In riparian forests, litter decay provides essential energy and nutrients for both terrestrial and fluvial ecosystems. Litter mixing effects (LMEs) are crucial in regulating litter decay and nutrient dynamics, yet how LMEs change over time is unclear in riparian forests. In this study, leaf litter of three common species (Alnus sibirica Fisch. ex Turcz, Betula platyphylla Sukaczev, and Betula fruticosa Pall.) were mixed in an equal mass ratio and LMEs were measured for mass and nitrogen (N) remaining in whole litter mixtures over a 3-year period in a boreal riparian forest, northeastern China. LMEs were also assessed for component litter mass and N remaining by separating litter mixtures by species. During the decay of litter mixtures, antagonistic effects on mass and N remaining were dominant after one and two years of decay, whereas only additive effects were observed after three years. LMEs correlated negatively with functional diversity after the first and two years of decay but disappeared after three years. When sorting litter mixtures by species, non-additive LMEs on mass and N remaining decreased over incubation time. Moreover, non-additive LMEs were more frequent for litter of both B. platyphylla and B. fruticosa with lower N concentration than for A. sibirica litter with higher N concentration. These results indicate that incubation time is a key determinant of litter mixing effects during decay and highlight that late-stage litter mixture decay may be predicted from single litter decay dynamics in boreal riparian forests.

Methanotrophs, organisms that obtain oxygen by oxidizing methane, are recognized as the only known biological sink for atmospheric CH₄, and forest soil methanotrophs play crucial roles in mitigating global warming. The succession patterns of methanotrophic communities and functions in Wudalianchi volcano forest soils could provide a basis for the study of evolutionary mechanisms between soil microorganisms, the environment, and carbon cycling of temperate forest ecosystems under climate change. In this study, the characteristics and drivers of methanotrophic community structure and function of two volcanic soils at different stages of development are analyzed, including an old volcano and a new volcano, which most recently erupted 300 years and 17 − 19 × 10⁵ years ago, respectively, and a non-volcano hills as control, based on space for time substitution and Miseq sequencing and bioinformation technology. The results showed that CH₄ fluxes were significantly higher in old-stage volcano forest soils than new-stage forest soils and non-volcano forest soils. There were significant differences in the community composition and diversity of soil methanotrophs from different volcano forest soils. Methylococcus was the dominant genus in all soil samples. Additionally, the relative abundance of Methylococcus, along with Clonothrix, Methyloglobulus, Methylomagum, Methylomonas and Methylosarcina, were the important genera responsible for the differences in methanotrophic community structure in different volcano forest soils. The relative abundance of methanotroph belonging to γ-proteobacteria was significantly higher than that belonging to α-proteobacteria (P < 0.05). Chao1, Shannon and Simpson indices of soil methanotrophic community were significantly lower in new-stage volcanos and were significantly affected by bulk density, total porosity, pH, nitrate, dissolved organic carbon and dissolved organic nitrogen. There were significant differences in community structure between new-stage and old-stage volcanoes. Bulk density and pH are important soil properties contributing to the divergence of methanotrophs community structure, and changes in soil properties due to soil development time are important factors driving differences in methanotrophs communities in Wudalianchi volcanic soils.

Afforestation has an important role in biodiversity conservation and ecosystem function improvement. A meta-analysis was carried out in China, which has the largest plantation area globally, to quantify the effects of plantings on soil microbial diversity. The results showed that the overall effect of afforestation on soil microbial diversity was positive across the country. Random forest algorithm suggested that soil carbon was the most important factor regulating microbial diversity and the positive response was only found with new plantings on low-carbon bare lands but not on high-carbon farmlands and grasslands. In addition, afforestation with broadleaved species increased microbial diversity, whereas planting with conifers had no effect on microbial diversity. This study clarified the effects of plantings on soil microbial diversity, which has an important implication for establishing appropriate policies and practices to improve the multiple functionalities (e.g., biodiversity conservation and climate change mitigation) during plantation establishment.

Effective development and utilization of wood resources is critical. Wood modification research has become an integral dimension of wood science research, however, the similarities between modified wood and original wood render it challenging for accurate identification and classification using conventional image classification techniques. So, the development of efficient and accurate wood classification techniques is inevitable. This paper presents a one-dimensional, convolutional neural network (i.e., BACNN) that combines near-infrared spectroscopy and deep learning techniques to classify poplar, tung, and balsa woods, and PVA, nano-silica-sol and PVA-nano silica sol modified woods of poplar. The results show that BACNN achieves an accuracy of 99.3% on the test set, higher than the 52.9% of the BP neural network and 98.7% of Support Vector Machine compared with traditional machine learning methods and deep learning based methods; it is also higher than the 97.6% of LeNet, 98.7% of AlexNet and 99.1% of VGGNet-11. Therefore, the classification method proposed offers potential applications in wood classification, especially with homogeneous modified wood, and it also provides a basis for subsequent wood properties studies.

Tree interactions are essential for the structure, dynamics, and function of forest ecosystems, but variations in the architecture of life-stage interaction networks (LSINs) across forests is unclear. Here, we constructed 16 LSINs in the mountainous forests of northwest Hebei, China based on crown overlap from four mixed forests with two dominant tree species. Our results show that LSINs decrease the complexity of stand densities and basal areas due to the interaction cluster differentiation. In addition, we found that mature trees and saplings play different roles, the first acting as “hub” life stages with high connectivity and the second, as “bridges” controlling information flow with high centrality. Across the forests, life stages with higher importance showed better parameter stability within LSINs. These results reveal that the structure of tree interactions among life stages is highly related to stand variables. Our efforts contribute to the understanding of LSIN complexity and provide a basis for further research on tree interactions in complex forest communities.

Light levels determine regeneration in stands and a key concern is how to regulate the light environment of different stand types to the requirements of the understory. In this study, we selected three stands typical in south China (a Cryptomeria japonica plantation, a Quercus acutissima plantation, and a mixed stand of both) and three thinning intensities to determine the best understory light environment for 3-year-old Phoebe bournei seedlings. The canopy structure, understory light environment, and photosynthesis and growth indicators were assessed following thinning. Thinning improved canopy structure and understory light availability of each stand; species composition was the reason for differences in the understory light environment. Under the same thinning intensity, the mixed stand had the greatest light radiation and most balanced spectral composition. P. bournei photosynthesis and growth were closely related to the light environment; all three stands required heavy thinning to create an effective and sustained understory light environment. In a suitable understory light environment, the efficiency of light interception, absorption, and use by seedlings was enhanced, resulting in a higher carbon assimilation the main limiting factor was stomatal conductance. As a shade-avoidance signal, red/far-red radiation is a critical factor driving changes in photosynthesis and growth of P. bournei seedlings, and a reduction increased light absorption and use capacity and height: diameter ratios. The growth advantage transformed from diameter to height, enabling seedlings to access more light. Our findings suggest that the regeneration of shade-tolerant species such as P. bournei could be enhanced if a targeted approach to thinning based on stand type was adopted.

Parameterization is a critical step in modelling ecosystem dynamics. However, assigning parameter values can be a technical challenge for structurally complex natural plant communities; uncertainties in model simulations often arise from inappropriate model parameterization. Here we compared five methods for defining community-level specific leaf area (SLA) and leaf C:N across nine contrasting forest sites along the North–South Transect of Eastern China, including biomass-weighted average for the entire plant community (AP_BW) and four simplified selective sampling (biomass-weighted average over five dominant tree species [5DT_BW], basal area weighted average over five dominant tree species [5DT_AW], biomass-weighted average over all tree species [AT_BW] and basal area weighted average over all tree species [AT_AW]). We found that the default values for SLA and leaf C:N embedded in the Biome-BGC v4.2 were higher than the five computational methods produced across the nine sites, with deviations ranging from 28.0 to 73.3%. In addition, there were only slight deviations (< 10%) between the whole plant community sampling (AP_BW) predicted NPP and the four simplified selective sampling methods, and no significant difference between the predictions of AT_BW and AP_BW except the Shennongjia site. The findings in this study highlights the critical importance of computational strategies for community-level parameterization in ecosystem process modelling, and will support the choice of parameterization methods.

Among the impacts of climate change, there is the intensification of phenomena such as the El Niño Southern Oscillation (ENSO) responsible for El Niño and La Niña. However, understanding their effects on the functional processes of forests is limited. Therefore, this study evaluated the effects of ENSO on litter stock and water holding capacity (WHC) in a successional forest in eastern Amazonia. Evaluations occurred in periods with the most rainfall in El Niño (2019) and least in La Niña (2021) years. Twelve permanent plots were used to sample litter. ENSO effects were evident for WHC, higher during El Niño. However, this influence was not clear for litter, as only in the rainy season effects were found. There was a positive correlation of WHC with precipitation and humidity, while litter stocks were negatively correlated with temperature and wind speed. Although the subject of this study requires long-term assessments, preliminary results suggests that, depending on the intensity of ENSO, forest functional processes can be strongly impacted and altered. The conclusion reinforces warnings by the scientific community about the impacts of climate change on the maintenance of litter stocks, decomposition and, consequently, the biogeochemical cycle and essential ecosystem services for the maintenance of Amazonia biodiversity. The need to develop long-term research to understand the effects of climatic change on litter stocks and water holding capacity is highlighted, especially in Amazonia.

As an important material for manufacturing resonant components of musical instruments, Paulownia has an important influence on the sound quality of Ruan. In this paper, a model for evaluating the sound quality of Ruan based on the vibration characteristics of wood is developed using machine learning methods. Generally, the selection of materials for Ruan manufacturing relies primarily on manually weighing, observing, striking, and listening by the instrument technician. Deficiencies in scientific theory have hindered the quality of the finished Ruan. In this study, nine Ruans were manufactured, and a prediction model of Ruan sound quality was proposed based on the raw material information of Ruans. Out of a total of 180 data sets, 145 and 45 sets were chosen for training and validation, respectively. In this paper, typical correlation analysis was used to determine the correlation between two single indicators in two adjacent pairwise combinations of the measured objects in each stage of the production process in Ruan. The vibration characteristics of the wood were tested, and a model for predicting the evaluation of Ruan’s acoustic qualities was developed by measuring the vibration characteristics of the resonating plate material. The acoustic quality of the Ruan sound board wood was evaluated and predicted using machine learning model generalized regression neural network. The results show that the prediction of Ruan sound quality can be achieved using Matlab simulation based on the vibration characteristics of the soundboard wood. When the model-predicted values were compared with the traditional predicted results, it was found that the generalized regression neural network had good performance, achieving an accuracy of 93.8% which was highly consistent with the experimental results. It was concluded that the model can accurately predict the acoustic quality of the Ruan based on the vibration performance of the soundboards.

There is considerable interest devoted to old-growth forests and their capacity to store carbon (C) in biomass and soil. Inventories of C stocks in old-growth forests are carried out worldwide, although there is a lack of information on their actual potential for C sequestration. To further understand this, soil organic carbon (SOC) was measured in one of Italy’s best-preserved old-growth forests, the Sasso Fratino Integral Nature Reserve. This reserve is on the World Heritage List along with other ancient beech forests of Europe, and it is virtually untouched due to the steepness of the terrain, even before legal constraints were imposed. Although the sandstone-derived soils are often shallow, they are rich in organic matter. However, no quantification had been carried out. By systematically sampling the topsoil across the forest, we accurately determined the average amount of SOC (62.0 ± 16.9 Mg ha^–1) and nitrogen (4.0 ± 1.2 Mg ha^–1) in the top 20 cm. Using the CENTURY model, future dynamics of SOC stocks were predicted to 2050 according to two climate scenarios, A1F1 and B2, the first of high concern and the second more optimistic. The model projected an increase of 0.2 and 0.3 Mg ha^–1 a^–1 by 2030 under the A1F1 and B2 scenarios, respectively, suggesting that the topsoil in old-growth forests does not reach equilibrium but continues accumulating SOC. However, from 2030 to 2050, a decline in SOC accumulation is predicted, indicating SOC net loss at high altitudes under the worst-case scenario. This study confirms that soils in old-growth forests play a significant role in carbon sequestration. It also suggests that climate change may affect the potential of these forests to store SOC not only in the long term but also in the coming years.

Heat shock transcription factors (Hsfs) have important roles during plant growth and development and responses to abiotic stresses. The identification and function of Hsf genes have been thoroughly studied in various herbaceous plant species, but not woody species, especially Phoebe bournei, an endangered, unique species in China. In this study, 17 members of the Hsf gene family were identified from P. bournei using bioinformatic methods. Phylogenetic analysis indicated that PbHsf genes were grouped into three subfamilies: A, B, and C. Conserved motifs, three-dimensional structure, and physicochemical properties of the PbHsf proteins were also analyzed. The structure of the PbHsf genes varied in the number of exons and introns. Prediction of cis-acting elements in the promoter region indicated that PbHsf genes are likely involved in responses to plant hormones and stresses. A collinearity analysis demonstrated that expansions of the PbHsf gene family mainly take place via segmental duplication. The expression levels of PbHsf genes varied across different plant tissues. On the basis of the expression profiles of five representative PbHsf genes during heat, cold, salt, and drought stress, PbHsf proteins seem to have multiple functions depending on the type of abiotic stress. This systematic, genome-wide investigation of PbHsf genes in P. bournei and their expression patterns provides valuable insights and information for further functional dissection of Hsf proteins in this endangered, unique species.

To study non-structural carbohydrate characteristics and nutrient utilization strategies of Pinus yunnanensis under continuous drought conditions, 2-year-old seedlings were planted in pots with appropriate water, light and moderate and severe drought treatments [(80 ± 5), (65 ± 5), (50 ± 5), and (35 ± 5)% of field water-holding capacity]. Non-structural carbohydrates, carbon (C), nitrogen (N), and phosphorus (P) concentrations were measured in each plant component. The results show that: (1) With increasing drought, non-structural carbohydrates gradually increased in leaves, stems, and coarse roots, while gradually decreased in fine roots; (2) C concentrations of all were relatively stable under different stress levels. Phosphorous utilization of each component increased under light and moderate drought conditions, while N and P utilization efficiency of each plant component decreased under severe drought. Growth was mainly restricted by N, first decreasing and then increasing with increased drought; (3) There was a correlation between the levels of non-structural carbohydrates and C, N, and P in each component. Changes in N concentration affected the interconversion between soluble sugar and starch, which play a regulatory role in the fluctuation of the concentration of non-structural carbohydrates; and, (4) Plasticity analysis showed that P. yunnanensis seedlings responded to drought mainly by altering starch concentration, the ratio of soluble sugar to starch in leaves and stems, and further by altering N and P utilization efficiencies. Overall, these results suggest that the physiological activities of all organs of P. yunnanensis seedlings are restricted under drought and that trade-offs exist between different physiological indicators and organs. Our findings are helpful in understanding non-structural carbohydrate and nutrient adaptation mechanisms under drought in P. yunnanensis seedlings.

Analyses of stable isotopes (C, O, H) in tree rings are increasingly important cross-disciplinary programs. The rapid development in this field documented in an increasing number of publications requires a comprehensive review. This study includes a bibliometric analysis-based review to better understand research trends in tree ring stable isotope research. Overall, 1475 publications were selected from the Web of Science Core Collection for 1974–2023. The findings are that: (1) numbers of annual publications and citations increased since 1974. From 1974 to 1980, there were around two relevant publications per year. However, from 2020 to 2022, this rose sharply to 109 publications per year. Likewise, average article citations were less than four per year before 1990, but were around four per article per year after 2000; (2) the major subjects using tree ring stable isotopes include forestry, geosciences, and environmental sciences, contributing to 42.5% of the total during 1974–2023; (3) the top three most productive institutions are the Chinese Academy of Sciences (423), the Swiss Federal Institute for Forest, Snow and Landscape Research (227), and the University of Arizona (204). These achievements result from strong collaborations; (4) review papers, for example, (Dawson et al., Annu Rev Ecol Syst 33:507–559, 2002) and (McCarroll and Loader, Quat Sci Rev 23:771–801, 2004), are among the most cited, with more than 1000 citations; (5) tree ring stable isotope studies mainly focus on climatology and ecology, with atmospheric CO₂ one of the most popular topics. Since 2010, precipitation and drought have received increasing attention. Based on this analysis, the research stages, key findings, debated issues, limitations and directions for future research are summarized. This study serves as an important attempt to understand the progress on the use of stable isotopes in tree rings, providing scientific guidance for young researchers in this field.

Birch has long suffered from a lack of active forest management, leading many researchers to use material without a detailed management history. Data collected from three birch (Betula pendula Roth, B. pubescens Ehrh.) sites in southern Sweden were analyzed using regression analysis to detect any trends or differences in wood properties that could be explained by stand history, tree age and stem form. All sites were genetics trials established in the same way. Estimates of acoustic velocity (AV) from non-destructive testing (NDT) and predicted AV had a higher correlation if data was pooled across sites and other stem form factors were considered. A subsample of stems had radial profiles of X-ray wood density and ring width by year created, and wood density was related to ring number from the pith and ring width. It seemed likely that wood density was negatively related to ring width for both birch species. Linear models had slight improvements if site and species were included, but only the youngest site with trees at age 15 had both birch species. This paper indicated that NDT values need to be considered separately, and any predictive models will likely be improved if they are specific to the site and birch species measured.

This study assessed the effect of patch scarification and mounding on the physical properties of the root layer and the success of tree planting in various types of forests. This study was conducted on 12 forest sites in taiga forests of the European part of Russia. A total of 54 plots were set up to assess seedling survival; root collar diameter, height, and heigh increment were measured for 240 seedlings to assess growth. In the rooting layer, 240 soil samples were taken to determine physical properties. The study showed that soil treatment methods had no effect on bulk density and total porosity in Cladina sites. However, reduced soil moisture was noted, particularly in mounds, resulting in increased aeration. In Myrtillus sites, there were increased bulk density, reduced soil moisture, and total porosity in the mounds. Mounding treatment in Polytrichum sites resulted in reduced soil moisture and increased aeration porosity. In the Myrtillus and Polytrichum sites, patch scarification had no effects on physical properties. In Polytrichum sites, survival rates, heights, and heigh increments of bareroot Norway spruce seedlings in mounds were higher than in patches; however, the same did not apply to diameter. In Cladina and Myrtillus sites, there was no difference in growth for bareroot and containerised seedlings with different soil treatments. Growing conditions and soil types should be considered when applying different soil treatment methods to ensure high survival rates and successful seedling growth.

Forest tree species reproduction is a key factor in maintaining the genetic diversity of future generations and the stability of forest ecosystems. The ongoing ash dieback disease could affect the reproductive ecology of Fraxinus excelsior L. and have a major impact on the quantity and quality of pollen and seeds. In this study, we investigated pollen production and viability of pollen and seeds of ash trees with different health status from 2018 to 2022. Inflorescences were collected from 105 trees (pollen production), pollen from 125 trees (pollen viability), and seeds from 53 trees (seed quality) in two seed orchards and in one floodplain forest in southern Germany. Not all parameters were examined at every site every year. The average pollen production per tree was estimated at 471.2 ± 647.9 billion pollen grains. In addition, we found that a high number of inflorescences did not equate to high pollen production per inflorescence. Pollen production of healthy and diseased trees did not differ significantly, although only 47% of severely diseased male trees (vs. 72% for healthy trees) produced flowers. With regards to pollen viability, the TTC test showed an average viability of 73% ± 17%. Overall, there was a slight tendency for diseased trees to have less viable pollen. However, a significant difference could only be calculated for trees in the floodplain forest. The percentage of germinable seeds in 2018 was 38% in the floodplain forest and 57% in one of the seed orchards. The percentage of viable seeds (TTC test) ranged from 17 to 22% in the orchards in 2020. Non-viable seeds were usually heavily infested by insects. In general, seed quality was not significantly different between healthy and diseased trees. Our results indicate that ash dieback affects flower formation and pollen viability but not pollen production or seed quality. Nevertheless, the fact that hardly any flowering was observed, especially for trees that were seriously affected, suggests a negative effect of ash dieback on reproductive performance. Thus, severely diseased trees will transfer their genes to a smaller extent to the next generation.

Atmospheric nitrogen (N) deposition is predicted to increase, especially in the subtropics. However, the responses of soil microorganisms to long-term N addition at the molecular level in N-rich subtropical forests have not been clarified. A long-term nutrient addition experiment was conducted in a subtropical evergreen old-growth forest in China. The four treatments were: control, low N (50 kg N ha⁻¹ a⁻¹), high N (100 kg N ha⁻¹ a⁻¹), and combined N and phosphorus (P) (100 kg N ha⁻¹ a⁻¹ + 50 kg P ha⁻¹ a⁻¹). Metagenomic sequencing characterized diversity and composition of soil microbial communities and used to construct bacterial/fungal co-occurrence networks. Nutrient-treated soils were more acidic and had higher levels of dissolved organic carbon than controls. There were no significant differences in microbial diversity and community composition across treatments. The addition of nutrients increased the abundance of copiotrophic bacteria and potentially beneficial microorganisms (e.g., Gemmatimonadetes, Chaetomium, and Aureobasidium). Low N addition increased microbiome network connectivity. Three rare fungi were identified as module hubs under nutrient addition, indicating that low abundance fungi were more sensitive to increased nutrients. The results indicate that the overall composition of microbial communities was stable but not static to long-term N addition. Our findings provide new insights that can aid predictions of the response of soil microbial communities to long-term N addition.

Thinning is an effective management step for sustainable forest development, yet less attention is paid to the restoration of soil microbiota after thinning. In this study, both abundant and rare soil microbial communities (i.e., bacterial, fungal), were evaluated under various thinning treatments in a mixed stand of Cunninghamia lanceolata and Sassafras tzumu using MiSeq sequencing. Thinning did not significantly change either abundant or rare bacterial and fungal community composition, but affected their alpha diversity. The Shannon– Wiener indexes of rare fungal taxa under medium thinning were significantly lower than in the light thinning (P < 0.05 level). Xanthobacteraceae dominated the abundant bacterial taxa, and Saitozyma and Mortierlla the abundant fungal taxa. The most common rare bacterial taxa varied; there was no prevalent rare fungal taxa under different thinnings. In addition, soil available nitrogen, total phosphorus, and pH had significant effects on rare bacterial taxa. Nutrients, especially available phosphorus, but not nitrogen, affected abundant and rare soil fungi. The results indicate that soil properties rather than plant factors affect abundant and rare microbial communities in soils of mixed stands. Thinning, through mediating soil properties, influences both abundant and rare bacterial and fungal communities in the mixed C. lanceolata and S. tzumu stand.

Due to the lack of a uniform and accurate definition of ‘drought’, several indicators have been introduced based on different variables and methods, and the efficiency of each of these is determined according to their relationship with drought. The relationship between two drought indices, SPI (standardized precipitation index) and SPEI (standardized precipitation-evapotranspiration index) in different seasons was investigated using annual rings of 15 tree samples to determine the effect of drought on the growth of oriental beech (Fagus orientalis Lipsky) in the Hyrcanian forests of northern Iran. The different evapotranspiration calculation methods were evaluated on SPEI efficiency based on Hargreaves-Samani, Thornthwaite, and Penman–Monteith methods using the step-by-step M5 decision tree regression method. The results show that SPEI based on the Penman–Monteith in a three-month time scale (spring) had similar temporal changes and a better relationship with annual tree rings (R ² = 0.81) at a 0.05 significant level. Abrupt change and a decreasing trend in the time series of annual tree rings are similar to the variation in the SPEI based on the Penman–Monteith method. Factors affecting evapotranspiration, temperature, wind speed, and sunshine hours (used in the Penman–Monteith method), increased but precipitation decreased. Using non-linear modeling methods, SPEI based on Penman–Monteith best illustrated climate changes affecting tree growth.

Tree-ring chronologies were developed for Sabina saltuaria and Abies faxoniana in mixed forests in the Qionglai Mountains of the eastern Tibetan Plateau. Climate-growth relationship analysis indicated that the two co-existing species reponded similarly to climate factors, although S. saltuaria was more sensitive than A. faxoniana. The strongest correlation was between S. saltuaria chronology and regional mean temperatures from June to November. Based on this relationship, a regional mean temperature from June to November for the period 1605–2016 was constructed. Reconstruction explained 37.3% of the temperature variance during th period 1961–2016. Six major warm periods and five major cold periods were identified. Spectral analysis detected significant interannual and multi-decadal cycles. Reconstruction also revealed the influence of the Atlantic Multi-decadal Oscillation, confirming its importance on climate change on the eastern Tibetan Plateau.

Forest fires are natural disasters that can occur suddenly and can be very damaging, burning thousands of square kilometers. Prevention is better than suppression and prediction models of forest fire occurrence have developed from the logistic regression model, the geographical weighted logistic regression model, the Lasso regression model, the random forest model, and the support vector machine model based on historical forest fire data from 2000 to 2019 in Jilin Province. The models, along with a distribution map are presented in this paper to provide a theoretical basis for forest fire management in this area. Existing studies show that the prediction accuracies of the two machine learning models are higher than those of the three generalized linear regression models. The accuracies of the random forest model, the support vector machine model, geographical weighted logistic regression model, the Lasso regression model, and logistic model were 88.7%, 87.7%, 86.0%, 85.0% and 84.6%, respectively. Weather is the main factor affecting forest fires, while the impacts of topography factors, human and social-economic factors on fire occurrence were similar.

On an agrosilvopastoral farm in central Italy where Maremmana cattle graze in Turkey oak forests, we evaluated the impact of different livestock densities on stand structure, tree diversity and natural regeneration in four types of grazed areas based on the grazing regime adopted: calf-grazed, high-intensity-grazed, low-intensity-grazed, ungrazed control. For each area, we set up three permanent circular plots (radius of 15 m) to survey the structural and dasometric characteristics of the overstorey, understorey, and regeneration layer. The results showed that grazing negatively affected the complexity of the forest structure and its potential to regenerate and maintain a high level of biodiversity. The differences in stand structure observed between the grazing areas were closely related to livestock density. The most sensitive components of the system were the understorey and the regeneration layers. Contrarily, the current grazing management did not affect the dominant tree structure or its composition. Our findings identified medium-term monitoring and regeneration management as the two significant aspects to consider when assessing sustainable livestock. New forests can be established by excluding grazing for about 20–25 years.

Quercus arkansana (Arkansas oak) is at risk of becoming endangered, as the total known population size is represented by a few isolated populations. The potential impact of climate change on this species in the near future is high, yet knowledge of its predicted effects is limited. Our study utilized the biomod2 R package to develop habitat suitability ensemble models based on bioclimatic and topographic environmental variables and the known locations of current distribution of Q. arkansana. We predicted suitable habitats across three climate change scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5) for 2050, 2070, and 2090. Our findings reveal that the current suitable habitat for Q. arkansana is approximately 127,881 km² across seven states (Texas, Arkansas, Alabama, Louisiana, Mississippi, Georgia, and Florida); approximately 9.5% is encompassed within state and federally managed protected areas. Our models predict that all current suitable habitats will disappear by 2050 due to climate change, resulting in a northward shift into new regions such as Tennessee and Kentucky. The large extent of suitable habitat outside protected areas suggests that a species-specific action plan incorporating protected areas and other areas may be crucial for its conservation. Moreover, protection of Q. arkansana habitat against climate change may require locally and regionally focused conservation policies, adaptive management strategies, and educational outreach among local people.

Needle chlorosis (NC) in Pinus taeda L. systems in Brazil becomes more frequent after second and third harvest rotation cycles. In a study to identify factors contributing to yellowing needle chorosis (YNC), trees were grown in soils originating from contrasting parent materials, and soils and needles (whole, green and chlorotic portions) from 1- and 2-year-old branches and the first and second needle flush release at four sites with YNC on P. taeda were analyzed for various elements and properties. All soils had very low base levels (Ca²⁺, Mg²⁺ and K⁺) and P, suggesting a possible lack of multiple elements. YNC symptoms started at needle tips, then extended toward the needle base with time. First flush needles had longer portions with YNC than second flush needles did. Needles from the lower crown also had more symptoms along their length than those higher in the canopy. Symptoms were similar to those reported for Mg. In chlorotic portions, Mg and Ca concentrations were well below critical values; in particular, Mg levels were only one third of the critical value of 0.3 g kg⁻¹. Collectively, results suggest that Mg deficiency is the primary reason for NC of P. taeda in various parent soils in Brazil.

In overlapping distribution areas of Sorbus pohuashanensis and S. discolor in North China (Mount Tuoliang, Mount Xiling and Mount Baihua), Sorbus individuals were found with pink fruit, which have never been recorded for the flora of China. Fourteen morphological characters combined with four chloroplast DNA markers and internal transcribed spacer (ITS) were used to analyze the origin of the Sorbus individuals with pink fruits and their relationship to S. pohuashanensis and S. discolor. PCA, SDA and one-way (taxon) ANOVA of morphological characters provided convincing evidence of the hybrid origin of Sorbus individuals with pink fruits based on a novel morphological character and many intermediate characters. Haplotype analysis based on four cpDNA markers showed that either S. pohuashanensis or S. discolor were maternal parents of Sorbus individuals with pink fruits. Incongruence of the position of Sorbus individuals with pink fruits between cpDNA and ITS in cluster trees supported by DNA sequence comparative analysis, implying former hybridization events between S. pohuashanensis and S. discolor. Multiple hybridization events between S. pohuashanensis and S. discolor might have contributed to the generation of Sorbus individuals with pink fruits. This study has provided insights into hybridization between species of the same genus in sympatric areas, which is of great significance for the study of interspecific hybridization.

The Tongbai Mountains is an ecologically sensitive region and the northern boundary of Pinus massoniana Lamb. To analyze the effect of different microenvironments on tree growth response to climate factors, we developed standard chronologies for earlywood width (EWW), latewood width (LWW), and total ring width (TRW) of P. massoniana at two sampling sites on slopes with different orientations, then analyzed characteristics of the chronologies and their correlations with climate variables from five stations in the region and with a regional normalized difference vegetation index (NDVI). Statistical results showed that the TRW/EWW/LWW chronology consistency and characteristics (mean sensitivity, signal to noise ratio, expressed population signal) for trees growing on the southeastern slope were much higher than for trees on the northeastern slope. Correlations indicated that temperature in current March and August has a significant positive effect on TRW/EWW/LWW formation, and the effect on the northeastern slope was weaker than on the southeastern slope. Compared to temperature, precipitation has more complicated effects on tree growth, but the effect on the northeastern slope was also generally weaker than on the southeastern slope. Stepwise linear regression analyses showed that temperature in August was the main limiting factor at the two sampling sites. Similarly, the response of tree growth on the southeastern slope as determined by the NDVI is better than on the northeastern slope, and the TRW/EWW/LWW chronologies for the southeastern slope explained over 50% of the total NDVI variances in June. Overall, the results indicate that the difference in the climate response of P. massoniana at two sampling sites is clearly caused by differences in the microenvironment, and such differences should be properly considered in future studies of forest dynamics and climate reconstructions.

Despite its enormous benefits, mining is responsible for intense changes to vegetation and soil properties. Thus, after extraction, it is necessary to rehabilitate the mined areas, creating better conditions for the establishment of plant species which is challenging. This study evaluated mineral and organic fertilization on the growth, and carbon and nitrogen (N) metabolism of two Crotalaria species [Crotalaria spectabilis (exotic species) and Crotalaria maypurensis (native species from Carajás Mineral Province (CMP)] established on a waste pile from an iron mine in CMP. A control (without fertilizer application) and six fertilization mixtures were tested (i = NPK; ii = NPK + micronutrients; iii = NPK + micronutrients + organic compost; iv = PK; v = PK + micronutrients; vi = PK + micronutrients + organic compost). Fertilization contributed to increased growth of both species, and treatments with NPK and micronutrients had the best results (up to 257% cf. controls), while organic fertilization did not show differences. Exotic Crotalaria had a greater number of nodules, higher nodule dry mass, chlorophyll a and b contents and showed free ammonium as the predominant N form, reflecting greater increments in biomass compared to native species. Although having lower growth, the use of this native species in the rehabilitation of mining areas should be considered, mainly because it has good development and meets current government legislation as an opportunity to restore local biodiversity.

A set of standard chronologies for tree-ring width (TRW), earlywood width (EWW) and latewood width (LWW) in Pinus tabuliformis Carr. along an altitudinal gradient (1450, 1400, and 1350 m a.s.l.) on Baiyunshan Mountain, Central China to analyze the effect of varying temperature and precipitation on growth along the gradient. Correlation analyses showed that at all three altitudes and the TRW and EWW chronologies generally had significant negative correlations with mean and maximum temperatures in the current April and May and with minimum temperatures in the prior July and August, but significant positive correlations with precipitation in the current May. Correlations were generally significantly negative between LWW chronologies and all temperatures in the prior July and August, indicating that the prior summer temperature had a strong lag effect on the growth of P. tabuliformis that increased with altitude. The correlation with the standardized precipitation evapotranspiration index (SPEI) confirmed that wet conditions in the current May promoted growth of TR and EW at all altitudes. Significant altitudinal differences were also found; at 1400 m, there were significant positive correlations between EWW chronologies and SPEI in the current April and significant negative correlations between LWW chronologies and SPEI in the current September, but these correlations were not significant at 1450 m. At 1350 m, there were also significant negative correlations between the TRW and the EWW chronologies and SPEI in the prior October and the current July and between LWW chronology and SPEI in the current August, but these correlations were not significant at 1400 m. Moving correlation results showed a stable response of EWW in relation to the SPEI in the current May at all three altitudes and of LWW to maximum temperature in the prior July–August at 1400 m from 2002 to 2018. The EWW chronology at 1400 m and the LWW chronology at 1450 m were identified as more suitable for climate reconstruction. These results provide a strong scientific basis for forest management decisions and climate reconstructions in Central China.

Tropical peat comprises decomposed dead plant material and acts like a sponge to absorb water, making it fully saturated. However, drought periods dry it readily and increases its vulnerability to fire. Peat fires emit greenhouse gases and particles contributing to haze, and prevention by constructing fire-break canals to reduce fire spread into forest reserves is crucial. This paper aims to determine peat physical and chemical properties near a fire-break canal at different fire frequency areas. Peat sampling was conducted at two forest reserves in Malaysia which represent low fire frequency and high fire frequency areas. The results show that peat properties were not affected by the construction of a fire-break canal, however lignin and cellulose content increased significantly from the distance of the canal in both areas. The study concluded that fire frequency did not significantly influence peat properties except for porosity. The higher fibre content in the high frequency area did not influence moisture content nor the ability to regain moisture. Thus, fire frequency might contribute differently to changes in physical and chemical properties, hence management efforts to construct fire- break canals and restoration efforts should protect peatlands from further degradation. These findings will benefit future management and planning for forest reserves.

In this study, we investigated how tree species affect N mineralization in connection to some soil properties and seconder metabolite levels of litter, in the soil of the oldest native forest communities. In the oldest pure communities of Pinus nigra (PN), Fagus orientalis (FO), and Abies bornmuelleriana (AB) in the mountain range of Mount Uludağ, Bursa, Turkey, annual net yield and N mineralization in the 0–5- and 5–20-cm soil layers were determined in a field incubation study over 1 year. Sampling locations were chosen from 1300 to 1600 m a.s.l., and moisture content (%), pH, water-holding capacity (%), organic C, total N, and C/N ratio, and annual net mineral N yield of the soil and hydrolyzed tannic acid and total phenolic compounds in litter were compared for these forest communities. F. orientalis had the highest annual net Nmin yield (43.9 ± 4.8 kg ha^–1 a^–1), P. nigra the lowest (30.5 ± 4.2 kg ha^–1 a^–1). Our findings show that in the oldest forest ecosystems, the seasonal soil moisture content and tree species play an essential role in N cycling and that hydrolyzed tannic acids and total phenolic compounds effectively control N turnover. Tannic acid and total phenolics in the litter were found to inhibit nitrification, but total phenolics were found to stimulate ammonification.

As a crucial component of terrestrial ecosystems, urban forests play a pivotal role in protecting urban biodiversity by providing suitable habitats for acoustic spaces. Previous studies note that vegetation structure is a key factor influencing bird sounds in urban forests; hence, adjusting the frequency composition may be a strategy for birds to avoid anthropogenic noise to mask their songs. However, it is unknown whether the response mechanisms of bird vocalizations to vegetation structure remain consistent despite being impacted by anthropogenic noise. It was hypothesized that anthropogenic noise in urban forests occupies the low-frequency space of bird songs, leading to a possible reshaping of the acoustic niches of forests, and the vegetation structure of urban forests is the critical factor that shapes the acoustic space for bird vocalization. Passive acoustic monitoring in various urban forests was used to monitor natural and anthropogenic noises, and sounds were classified into three acoustic scenes (bird sounds, human sounds, and bird-human sounds) to determine interconnections between bird sounds, anthropogenic noise, and vegetation structure. Anthropogenic noise altered the acoustic niche of urban forests by intruding into the low-frequency space used by birds, and vegetation structures related to volume (trunk volume and branch volume) and density (number of branches and leaf area index) significantly impact the diversity of bird sounds. Our findings indicate that the response to low and high frequency signals to vegetation structure is distinct. By clarifying this relationship, our results contribute to understanding of how vegetation structure influences bird sounds in urban forests impacted by anthropogenic noise.

Forest degradation induced by intensive forest management and temperature increase by climate change are resulting in biodiversity decline in boreal forests. Intensive forest management and high-end climate emission scenarios can further reduce the amount and diversity of deadwood, the limiting factor for habitats for saproxylic species in European boreal forests. The magnitude of their combined effects and how changes in forest management can affect deadwood diversity under a range of climate change scenarios are poorly understood. We used forest growth simulations to evaluate how forest management and climate change will individually and jointly affect habitats of red-listed saproxylic species in Finland. We simulated seven forest management regimes and three climate scenarios (reference, RCP4.5 and RCP8.5) over 100 years. Management regimes included set aside, continuous cover forestry, business-as-usual (BAU) and four modifications of BAU. Habitat suitability was assessed using a species-specific habitat suitability index, including 21 fungal and invertebrate species groups. “Winner” and “loser” species were identified based on the modelled impacts of forest management and climate change on their habitat suitability. We found that forest management had a major impact on habitat suitability of saproxylic species compared to climate change. Habitat suitability index varied by over 250% among management regimes, while overall change in habitat suitability index caused by climate change was on average only 2%. More species groups were identified as winners than losers from impacts of climate change (52%–95% were winners, depending on the climate change scenario and management regime). The largest increase in habitat suitability index was achieved under set aside (254%) and the climate scenario RCP8.5 (> 2%), while continuous cover forestry was the most suitable regime to increase habitat suitability of saproxylic species (up to + 11%) across all climate change scenarios. Our results show that close-to-nature management regimes (e.g., continuous cover forestry and set aside) can increase the habitat suitability of many saproxylic boreal species more than the basic business-as-usual regime. This suggests that biodiversity loss of many saproxylic species in boreal forests can be mitigated through improved forest management practices, even as climate change progresses.

Budding is an important grafting technique to asexually propagate pecan (Carya illinoinensis (Wangenh.) K. Koch). To determine factors that might hamper successful budding of the species, a representative easy-to-survive cultivar ‘Pawnee’ and a typical difficult-to-survive cultivar ‘Jinhua’ were used for comprehensive analysis. Morphological observation showed that cells surrounding the secretory cells or sieve tube had collapsed in ‘Jinhua’ but not in ‘Pawnee’ during grafting. ‘Jinhua’ might suffer more hypoxia stress than ‘Pawnee’ as ‘Jinhua’ had higher catalase, superoxide dismutase, polyphenol oxidase, pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH) activities during grafting and contained greater levels of hydrogen peroxide 12 days after grafting (DAG). Transcriptions of PDC and ADH were also up-regulated significantly in ‘Jinhua’ whereas they were not significantly affected in ‘Pawnee’. Phenylalanine ammonia-lyase activities of ‘Jinhua’ were consistently lower than that of ‘Pawnee’. Initial phenol contents were similar between the two cultivars. Graft-promoting substances, including soluble sugar, soluble protein, and gibberellin (GA) were incompletely recovered in ‘Jinhua’ 12 DAG while fully restored in ‘Pawnee’. Increased levels of trans-zeatin riboside in ‘Jinhua’ were much smaller than in ‘Pawnee’ 3 DAG. The contents of indole-3-acetic acid were similar, and the dynamics of abscisic acid were the same between the two genotypes. Results suggest that hypoxia stress and shortages of sugar, protein, GA, and cytokinin during the healing process might be key factors limiting successful budding of pecan. The degree of scion-rootstock compatibility and the content of phenols might be excluded as constraints for successful budding.

Differences in forest attributes and carbon sequestration of each organ and layer between broadleaved and conifer forests of central and outer urban areas are not well-defined, hindering the precise management of urban forests and improvement of function. To clarify the effect of two forest types with different urbanization intensities, we determined differences in vegetation composition and diversity, structural traits, and carbon stocks of 152 plots (20 m × 20 m) in urban park forests in Changchun, which had the largest green quantity and carbon density effectiveness. We found that 1.1-fold thicker and healthier trees, and 1.6- to 2.0-fold higher, healthier, denser, and more various shrubs but with sparser trees and herbs occurred in the central urban forests (p < 0.05) than in the outer forests. The conifer forests exhibited 30–70% obviously higher tree aboveground carbon sequestration (including stem and leaf) and 20% bigger trees, especially in the outer forests (p < 0.05). In contrast, 1.1- to 1.5-fold higher branch stocks, healthier and more diverse trees were found in broadleaved forests of both the inner and outer forests (p < 0.05). Plant size and dominant species had similarly important roles in carbon stock improvement, especially big-sized woody plants and Pinus tabuliformis. In addition, a higher number of deciduous or needle species positively affected the broadleaved forest of the central urban area and conifer forest of the outer urban area, respectively. These findings can be used to guide precise management and accelerate the improvement of urban carbon function in Northeast China in the future.

Minimum temperatures have remarkable impacts on tree growth at high-elevation sites on the Tibetan Plateau, but the shortage of long-term and high-resolution paleoclimate records inhibits understanding of recent minimum temperature anomalies. In this study, a warm season (April–September) reconstruction is presented for the past 467 years (1550–2016) based on Sabina tibetica ring-width chronology on the Lianbaoyeze Mountain of the central eastern Tibetan Plateau. Eight warm periods and eight cold periods were identified. Long-term minimum temperature variations revealed a high degree of coherence with nearby reconstructions. Spatial correlations between our reconstruction and global sea surface temperatures suggest that warm season minimum temperature anomalies in the central eastern Tibetan Plateau were strongly influenced by large-scale ocean atmospheric circulations, such as the El Niño-Southern Oscillation and the Atlantic Multidecadal Oscillation.

Discerning vulnerability differences among different aged trees to drought-driven growth decline or to mortality is critical to implement age-specific countermeasures for forest management in water-limited areas. An important species for afforestation in dry environments of northern China, Mongolian pine (Pinus sylvestris var. mongolica Litv.) has recently exhibited growth decline and dieback on many sites, particularly pronounced in old-growth plantations. However, changes in response to drought stress by this species with age as well as the underlying mechanisms are poorly understood. In this study, tree-ring data and remotely sensed vegetation data were combined to investigate variations in growth at individual tree and stand scales for young (9 − 13 years) and aging (35 − 52 years) plantations of Mongolian pine in a water-limited area of northern China. A recent decline in tree-ring width in the older plantation also had lower values in satellited-derived normalized difference vegetation indices and normalized difference water indices relative to the younger plantations. In addition, all measured growth-related metrics were strongly correlated with the self-calibrating Palmer drought severity index during the growing season in the older plantation. Sensitivity of growth to drought of the older plantation might be attributed to more severe hydraulic limitations, as reflected by their lower sapwood- and leaf-specific hydraulic conductivities. Our study presents a comprehensive view on changes of growth with age by integrating multiple methods and provides an explanation from the perspective of plant hydraulics for growth decline with age. The results indicate that old-growth Mongolian pine plantations in water-limited environments may face increased growth declines under the context of climate warming and drying.

Extreme climate has increasingly led to negative impacts on forest ecosystems globally, especially in semiarid areas where forest ecosystems are more vulnerable. However, it is poorly understood how tree growth is affected by different drought events. In 2006–2009, the larch plantations in the semiarid areas of Northwest China were negatively affected by four consecutive dry years, which was a very rare phenomenon that may occur frequently under future climate warming. In this study, we analyzed the effect of these consecutive dry years on tree growth based on the data of the tree rings in the dominant layer of the forest canopy on a larch plantation. We found that the tree-ring width index (RWI) in dry years was lower than that in normal years, and it experienced a rapidly decreasing trend from 2006 to 2009 (slope =  − 0.139 year⁻¹, r =  − 0.94) due to water supply deficits in those dry years. Drought induced legacy effects of tree growth reduction, and consecutive dry years corresponded with greater growth reductions and legacy effects. Growth reductions and legacy effects were significantly stronger in the third and fourth consecutive dry years than that of single dry year (p < 0.05), which might have been due to the cumulative stress caused by consecutive dry years. Our results showed that larch trees experienced greater tree growth reduction due to consecutive dry years and their legacy effect, and the trees had lower recovery rates after consecutive dry years. Our results highlight that consecutive dry years pose a new threat to plantations under climate warming, and thus, the effect of climate extremes on tree growth should be considered in growth models in semiarid areas.

Global warming will affect growth strategies and how trees will adapt. To compare the response of tree radial growth to climate warming in different slope directions, samples of Pinus armandii Franch were collected and tree-ring chronologies developed on northern and western slopes from the Lubanling in the Funiu Mountains. Correlation analyses showed that two chronologies were mainly limited by temperatures in the previous June–August and the combination of temperatures and moisture in the current May–July. The difference of the climate response to slopes was small but not negligible. Radial growth of the LBL01 site on the northern slope was affected by the combined maximum and minimum temperatures, while that of the LBL02 site was affected by maximum temperatures. With regards to moisture, radial growth of the trees on the north slope was influenced by the relative humidity in the current May–July, while on the western slope, it was affected by the relative humidity in the previous June–August, the current May–July and the precipitation in the current May–July. With the change in climate, the effects of the main limiting factors on growth on different slopes were visible to a certain extent, but the differences in response of trees on different slopes gradually decreased, which might be caused by factors such as different slope directions and the change in diurnal temperature range. These results may provide information for forest protection and ecological construction in this region, and a scientific reference for future climate reconstruction.

Native grasslands in the Pampas of South America are increasingly being replaced by Eucalyptus and Pinus stands. The short rotation regimes used for the stands require high nutrient levels, with litterfall being a major source of nutrient return. To model the litterfall production using climatic variables and assess the nutrient return in 14-year-old Eucalyptus grandis and Pinus taeda stands, we measured litter production over 2 years, using conical litter traps, and monitored climatic variables. Mean temperature, accumulated precipitation, and mean maximum vapor pressure deficit at the seasonal level influenced litterfall production by E. grandis; seasonal accumulated precipitation and mean maximum temperature affected litterfall by P. taeda. The regression tree modeling based on these climatic variables had great accuracy and predictive power for E. grandis (N = 33; MAE (mean absolute error) = 0.65; RMSE (root mean square error) = 0.91; R ² = 0.71) and P. taeda (N = 108; MAE = 1.50; RMSE = 1.59; R ² = 0.72). The nutrient return followed a similar pattern to litterfall deposition, as well as the order of importance of macronutrients (E. grandis: Ca > N > K > Mg > P; P. taeda: N > Ca > K > Mg > P) and micronutrients (E. grandis and P. taeda: Mn > Fe > Zn > Cu) in both species. This study constitutes a first approximation of factors that affect litterfall and nutrient return in these systems.

Increasing human activity is altering the structure of forests, which affects the composition of communities, including birds. However, little is known about the key forest structure variables that determine the richness of bird communities in European temperate oak forests. We, therefore, aimed to identify key variables in these habitats that could contribute to the design of management strategies for forest conservation by surveying 11 oak-dominated forest sites throughout the mid-mountain range of Hungary at 86 survey points to reveal the role of different compositional and structural variables for forest stands that influence the breeding bird assemblages in the forests at the functional group and individual species levels. Based on decision tree modelling, our results showed that the density of trees larger than 30 cm DBH was an overall important variable, indicating that large-diameter trees were essential to provide diverse bird communities. The total abundance of birds, the foliage-gleaners, primary and secondary cavity nesters, residents, and five specific bird species were related to the density of high trunk diameter trees. The abundance of shrub nesters was negatively influenced by a high density of trees over 10 cm DBH. The density of the shrub layer positively affected total bird abundance and the abundance of foliage gleaners, secondary cavity nesters and residents. Analysis of the co-dominant tree species showed that the presence of linden, beech, and hornbeam was important in influencing the abundance of various bird species, e.g., Eurasian Treecreeper (Certhia familiaris), Marsh Tit (Poecile palustris) and Wood Warbler (Phylloscopus sibilatrix). Our results indicated that large trees, high tree diversity, and dense shrub layer were essential for forest bird communities and are critical targets for protection to maintain diverse and abundant bird communities in oak-dominated forest habitats.

As one of the regions most affected by global climate warming, the Tianshan mountains has experienced several ecological crises, including retreating glaciers and water deficits. Climate warming in these mountains is considered mainly to be caused by increases in minimum temperatures and winter temperatures, while the influence of maximum temperatures is unclear. In this study, a 300-year tree-ring chronology developed from the Western Tianshan Mountains was used to reconstruct the summer (June–August) maximum temperature (T _max6–8) variations from 1718 to 2017. The reconstruction explained 53.1% of the variance in the observed T _max6–8. Over the past 300 years, the T _max6–8 reconstruction showed clear interannual and decadal variabilities. There was a significant warming trend (0.18 °C/decade) after the 1950s, which was close to the increasing rates of the minimum and mean temperatures. The increase in maximum temperature was also present over the whole Tianshan mountains and its impact on climate warming has increased. The T _max6-8 variations in the Western Tianshan mountains were influenced by frequent volcanic eruptions combined with the influence of solar activity and the summer North Atlantic Oscillation. This study reveals that climate warming is significantly influenced by the increase in maximum temperatures and clarifies possible driving mechanisms of temperature variations in the Western Tianshan mountains which should aid climate predictions.

Research has indicated that simple forest ecosystem composition, structure and diversity have uncomplicated community relationships and insufficient pest control capabilities. To investigate changing characteristics of plant and insect communities in under pest outbreaks in Larix principis-rupprechtii plantations, the research areas were defined as mature (48–50 years) and young (24–29 years) infested stands along with healthy stands. The results show a reduction in the complexity and diversity of plant communities and herbaceous plant guilds (polycultures of beneficial plants) and the complexity and dominance of insect communities, especially natural insect enemies. The results also show the relative simplicity of the main factors of community change and development that represent the characteristics of pest outbreaks in L. principis-rupprechtii plantations. The complexity and diversity of plant communities, particularly herbaceous plant guilds play a fundamental role in the regulation and development in forest ecosystems.

Disturbances such as forest fires, intense winds, and insect damage exert strong impacts on forest ecosystems by shaping their structure and growth dynamics, with contributions from climate change. Consequently, there is a need for reliable and operational methods to monitor and map these disturbances for the development of suitable management strategies. While susceptibility assessment using machine learning methods has increased, most studies have focused on a single disturbance. Moreover, there has been limited exploration of the use of “Automated Machine Learning (AutoML)” in the literature. In this study, susceptibility assessment for multiple forest disturbances (fires, insect damage, and wind damage) was conducted using the PyCaret AutoML framework in the Izmir Regional Forest Directorate (RFD) in Turkey. The AutoML framework compared 14 machine learning algorithms and ranked the best models based on AUC (area under the curve) values. The extra tree classifier (ET) algorithm was selected for modeling the susceptibility of each disturbance due to its good performance (AUC values > 0.98). The study evaluated susceptibilities for both individual and multiple disturbances, creating a total of four susceptibility maps using fifteen driving factors in the assessment. According to the results, 82.5% of forested areas in the Izmir RFD are susceptible to multiple disturbances at high and very high levels. Additionally, a potential forest disturbances map was created, revealing that 15.6% of forested areas in the Izmir RFD may experience no damage from the disturbances considered, while 54.2% could face damage from all three disturbances. The SHAP (Shapley Additive exPlanations) methodology was applied to evaluate the importance of features on prediction and the nonlinear relationship between explanatory features and susceptibility to disturbance.

Episodes of drought-induced decline in tree growth and mortality are becoming more frequent as a result of climate warming and enhanced water stress in semi-arid areas. However, the ecophysiological mechanisms underlying the impact of drought on tree growth remains unresolved. In this study, earlywood and latewood tree-ring growth, δ¹³C, and δ¹⁸O chronologies of Picea mongolica from 1900 to 2013 were developed to clarify the intra- and inter-annual tree-ring growth responses to increasingly frequent droughts. The results indicate that annual basal area increment residuals (BAI_res), which removed tree age and size effects, have significantly decreased since 1960. However, the decreasing trend of earlywood BAI_res was higher than that of latewood. Climate response analysis suggests that the dominant parameters for earlywood and latewood proxies (BAI_res, δ¹³C and δ¹⁸O) were drought-related climate variables (Palmer drought severity index, temperature, relative humidity, and vapor pressure deficit). The most significant period of earlywood and latewood proxies’ responses to climate variables were focused on June–July and July–August, respectively. BAI_res, and δ¹³C were significantly affected by temperature and moisture conditions, whereas δ¹⁸O was slightly affected. Decreasing stomatal conductance due to drought outweighed the influence of increasing CO₂ on intrinsic water use efficiency (iWUE), and ultimately led to a decline in BAI_res. Compared to latewood, the faster decreasing BAI_res and smaller increasing iWUE of earlywood suggested trees were more vulnerable to water stress in the early growing season. Our study provides insights into the inter- and intra-annual mechanisms of tree-ring growth in semi-arid regions under rising CO₂ and climate change.

Prediction, prevention, and control of forest fires are crucial on at all scales. Developing effective fire detection systems can aid in their control. This study proposes a novel CNN (convolutional neural network) using an attention blocks module which combines an attention module with numerous input layers to enhance the performance of neural networks. The suggested model focuses on predicting the damage affected/burned areas due to possible wildfires and evaluating the multilateral interactions between the pertinent factors. The results show the impacts of CNN using attention blocks for feature extraction and to better understand how ecosystems are affected by meteorological factors. For selected meteorological data, RMSE 12.08 and MAE 7.45 values provide higher predictive power for selecting relevant and necessary features to provide optimal performance with less operational and computational costs. These findings show that the suggested strategy is reliable and effective for planning and managing fire-prone regions as well as for predicting forest fire damage.

Populus alba ‘Berolinensis’ is a fast-growing, high-yielding species with strong biotic and abiotic stress resistance, and widely planted for timber, shelter belts and aesthetic purposes. In this study, molecular development is explored and the important genes regulating xylem formation in P. alba ‘Berolinensis’ under artificial bending treatments was identified. Anatomical investigation indicated that tension wood (TW) was characterized by eccentric growth of xylem and was enriched in cellulose; the degree of lignification was lower than for normal wood (NW) and opposite wood (OW). RNA-Seq-based transcriptome analysis was performed using developing xylem from three wood types (TW, OW and NW). A large number of differentially expressed genes (DEGs) were screened and 4889 counted. In GO and KEGG enrichment results, genes involved in plant hormone signal transduction, phenylpropanoid biosynthesis, and cell wall and secondary cell wall biogenesis play major roles in xylem development under artificial bending. Eight expansin (PalEXP) genes were identified from the RNA-seq data; four were differentially expressed during tension wood formation. Phylogenetic analysis indicated that PalEXLB1 belongs to the EXPB subfamily and that the other PalEXPs are members of the EXPA subfamily. A transcriptional regulatory network construction showed 10 transcription factors located in the first and second layers upstream of EXP, including WRKY, ERF and bHLH. RT‒qPCR analysis in leaves, stems and roots combined with transcriptome analysis suggests that PalEXPA2, PalEXPA4 and PalEXPA15 play significant regulatory roles in cell wall formation during tension wood development. The candidate genes involved in xylem cell wall development during tension wood formation marks an important step toward identifying the molecular regulatory mechanism of xylem development and wood property improvement in P. alba ‘Berolinensis’.

Quantifying the biomass of saplings in the regeneration component is critical for understanding biogeochemical processes of forest ecosystems. However, accurate allometric equations have yet to be developed in sufficient detail. To develop species-specific and generalized allometric equations, 154 saplings of eight Fagaceae tree species in subtropical China’s evergreen broadleaved forests were collected. Three dendrometric variables, root collar diameter (d), height (h), and crown area (ca) were applied in the model by the weighted nonlinear seemingly unrelated regression method. Using only d as an input variable, the species-specific and generalized allometric equations estimated the aboveground biomass reasonably, with

values generally > 0.85. Adding h and/or ca improved the fitting of some biomass components to a certain extent. Generalized equations showed a relatively large coefficient of variation but comparable bias to species-specific equations. Only in the absence of species-specific equations at a given location are generalized equations for mixed species recommended. The developed regression equations can be used to accurately calculate the aboveground biomass of understory Fagaceae regeneration trees in China’s subtropical evergreen broadleaved forests.

The role of the temperate mixed broadleaf-Korean pine forest (BKF) in global biogeochemical cycles will depend on how the tree species community responds to climate; however, species-specific responses and vulnerabilities of common trees in BKF to extreme climates are poorly understood. Here we used dendrochronological methods to assess radial growth of seven main tree species (Pinus koraiensis, Picea jezoensis, Abies nephrolepis, Fraxinus mandshurica, Phellodendron amurense, Quercus mongolica, and Ulmus davidiana) in an old-growth BKF in response to climate changes in the Xiaoxing’an Mountains and to improve predictions of changes in the tree species composition. Temperature in most months and winter precipitation significantly negatively affected growth of P. jezoensis and A. nephrolepis, but positively impacted growth of P. koraiensis and the broadleaf species, especially F. mandshurica and U. davidiana. Precipitation and relative humidity in June significantly positively impacted the growth of most tree species. The positive effect of the temperature during the previous non-growing season (PNG) on growth of F. mandshurica and Q. mongolica strengthened significantly with rapid warming around 1981, while the impact of PNG temperature on the growth of P. jezoensis and A. nephrolepis changed from significantly negative to weakly negative or positive at this time. The negative response of radial growth of P. jezoensis and A. nephrolepis to precipitation during the growing season gradually weakened, and the negative response to PNG precipitation was enhanced. Among the studied species, P. koraiensis was the most resistant to drought, and U. davidiana recovered the best after extreme drought. Ulmus davidiana, P. jezoensis and A. nephrolepis were more resistant to extreme cold than the other species. Climate warming generally exacerbated the opposite growth patterns of conifer (decline) and broadleaf (increase) species. Deciduous broadleaf tree species in the old-growth BKF probably will gradually become dominant as warming continues. Species-specific growth-climate relationships should be considered in future models of biogeochemical cycles and in forestry management practices.

Research on fires at the wildland-urban interface (WUI) has generated significant insights and advancements across various fields of study. Environmental, agriculture, and social sciences have played prominent roles in understanding the impacts of fires in the environment, in protecting communities, and addressing management challenges. This study aimed to create a database using a text mining technique for global researchers interested in WUI-projects and highlighting the interest of countries in this field. Author’s-Keywords analysis emphasized the dominance of fire science-related terms, especially related to WUI, and identified keyword clusters related to the WUI fire-risk-assessment-system—“exposure”, “danger”, and “vulnerability” within wildfire research. Trends over the past decade showcase shifting research interests with a growing focus on WUI fires, while regional variations highlighted that the “exposure” keyword cluster received greater attention in the southern Europe and South America. However, vulnerability keywords have relatively a lower representation across all regions. The analysis underscores the interdisciplinary nature of WUI research and emphasizes the need for targeted approaches to address the unique challenges of the wildland-urban interface. Overall, this study provides valuable insights for researchers and serves as a foundation for further collaboration in this field through the understanding of the trends over recent years and in different regions.

Forest productivity is closely linked to seasonal variations and vertical differentiation in leaf traits. However, leaf structural and chemical traits variation among co-existing species, and plant functional types within the canopy are poorly quantified. In this study, the seasonality of leaf chlorophyll, nitrogen (N), and phosphorus (P) were quantified vertically along the canopy of four major tree species and two types of herbs in a temperate deciduous forest. The role of shade tolerance in shaping the seasonal variation and vertical differentiation was examined. During the entire season, chlorophyll content showed a distinct asymmetric unimodal pattern for all species, with greater chlorophyll levels in autumn than in spring, and the timing of peak chlorophyll per leaf area gradually decreased as shade tolerance increased. Chlorophyll a:b ratios gradually decreased with increasing shade tolerance. Leaf N and P contents sharply declined during leaf expansion, remained steady in the mature stage and decreased again during leaf senescence. Over the seasons, the lower canopy layer had significantly higher chlorophyll per leaf mass but not chlorophyll per leaf area than the upper canopy layer regardless of degree of shade tolerance. However, N and P per leaf area of intermediate shade-tolerant and fully shade-tolerant tree species were significantly higher in the upper canopy than in the lower. Seasonal variations in N:P ratios suggest changes in N or P limitation. These findings indicate that shade tolerance is a key feature shaping inter-specific differences in leaf chlorophyll, N, and P contents as well as their seasonality in temperate deciduous forests, which have significant implications for modeling leaf photosynthesis and ecosystem production.

Acorn production in oak (Quercus spp.) shows considerable inter-annual variation, known as masting, which provides a natural defence against seed predators but a highly-variable supply of acorns for uses such as in commercial tree planting each year. Anthropogenic emissions of greenhouse gases have been very widely reported to influence plant growth and seed or fruit size and quantity via the ‘fertilisation effect’ that leads to enhanced photosynthesis. To examine if acorn production in mature woodland communities will be affected by further increase in CO₂, the contents of litter traps from a Free Air Carbon Enrichment (FACE) experiment in deciduous woodland in central England were analysed for numbers of flowers and acorns of pedunculate oak (Quercus robur L.) at different stages of development and their predation levels under ambient and elevated CO₂ concentrations. Inter-annual variation in acorn numbers was considerable and cyclical between 2015 and 2021, with the greatest numbers of mature acorns in 2015, 2017 and 2020 but almost none in 2018. The numbers of flowers, enlarged cups, immature acorns, empty acorn cups, and galls in the litter traps also varied amongst years; comparatively high numbers of enlarged cups were recorded in 2018, suggesting Q. robur at this site is a fruit maturation masting species (i.e., the extent of abortion of pollinated flowers during acorn development affects mature acorn numbers greatly). Raising the atmospheric CO₂ concentration by 150 μL L⁻¹, from early 2017, increased the numbers of immature acorns, and all acorn evidence (empty cups + immature acorns + mature acorns) detected in the litter traps compared to ambient controls by 2021, but did not consistently affect the numbers of flowers, enlarged cups, empty cups, or mature acorns. The number of flowers in the elevated CO₂ plots’ litter traps was greater in 2018 than 2017, one year after CO₂ enrichment began, whereas numbers declined in ambient plots. Enrichment with CO₂ also increased the number of oak knopper galls (Andricus quercuscalicis Burgsdorf). We conclude that elevated CO₂ increased the occurrence of acorns developing from flowers, but the putative benefit to mature acorn numbers may have been hidden by excessive pre- and/or post-dispersal predation. There was no evidence that elevated CO₂ altered masting behaviour.

Vegetation productivity on the southern edge of the Inner Mongolian Plateau, which plays a vital role in the ecological environment and in the arable and pastoral production in this region, can be characterized by the NDVI (normalized difference vegetation index). However, the observed NDVI data span only the last ~ 40 years. The growth of Pinus tabulaeformis Carr. is strongly correlated with the NDVI, making it a valuable proxy for extending the length of observed NDVI datasets. In this study, we reconstructed an NDVI series for 1776–2021 for the Daqing Mountains, based on a tree-ring width chronology. The reconstructed data accounted for 55% of the variance in the observed data, and its statistical characteristics and validation indicate that the reconstruction is dependable. Spatial correlation analysis demonstrated the consistency of climate signals in central Inner Mongolia in both the arable and pastoral zones. The results of superposed epoch analysis revealed a good temporal consistency between drought and flood events and the reconstructed NDVI sequence in this region.

Tree canopies influence atmospheric pollutant depositions depending on type, ecosystem characteristics, and local climatic conditions. This study investigated the impact of Pinus sylvestris L. and Picea abies (L.) H. Karst., and a mixture of both, on the chemical composition of precipitation. Three permanent plots within the ICP forest level II monitoring network in Lithuania were selected to illustrate typical hemiboreal coniferous forests. The study analysed (1) the concentrations of NO₂, NH₃ and SO₂ in the ambient air; (2) the concentrations of SO₄ ²⁻, NO₃ ⁻, NH₄ ⁺, Na⁺, K⁺, Ca²⁺ and Cl^– in throughfall beneath canopies and in precipitation collected in an adjacent field, and (3) S and total N, Na⁺, K⁺, Ca²⁺ and Cl⁻ depositions in throughfall and precipitation over 2006–2022. Results show a significant decrease in SO₂ emissions in the ambient air; NO₂ and NH₃ emissions also decreased. The canopies reduced the acidity of throughfall, although they led to notably higher concentrations of SO₄ ²⁻, NO₃ ⁻, Na⁺, and particularly K⁺. During the study, low variability in NO₃ ^– deposition and a decrease in NH₄ ⁺ deposition occurred. Deposition loads increased by 20–30% when precipitation passed through the canopy. The cumulative deposition of S, Cl, Na, K, Ca, and N was greater under P. abies than under P. sylvestris. However, K deposition in throughfall was considerably lower under P. sylvestris compared to the P. abies or mixed stand. Throughfall S depositions declined across all three coniferous plots. Overall, there was no specific effect of tree species on throughfall chemistry.

Temporal changes in the relationship between tree growth and climate have been observed in numerous forests across the world. The patterns and the possible regulators (e.g., forest community structure) of such changes are, however, not well understood. A vegetation survey and analyses of growth-climate relationships for Abies georgei var. Smithii (Smith fir) forests were carried along an altitudinal gradient from 3600 to 4200 m on Meili Snow Mountain, southeastern Tibetan Plateau. The results showed that the associations between growth and temperature have declined since the 1970s over the whole transect, while response to standardized precipitation-evapotranspiration indices (SPEI) strengthened in the mid- and lower-transect. Comparison between growth and vegetation data showed that tree growth was more sensitive to drought in stands with higher species richness and greater shrub cover. Drought stress on growth may be increased by heavy competition from shrub and herb layers. These results show the non-stationary nature of tree growth-climate associations and the linkage to forest community structures. Vegetation components should be considered in future modeling and forecasting of forest dynamics in relation to climate changes.

Urbanization has resulted in a significant degradation of soil quality, subjecting plants to persistent abiotic stressors such as heavy metal pollution, salinization, and drought. UDP-glycosyltransferases (UGTs) participate in protein glycosylation, secondary metabolite synthesis, and detoxification of exogenous toxic substances. Iris sanguinea Donn ex Hornem exhibits a high degree of resistance to various abiotic stressors. To enhance the plant’s response to adversity, a novel glycosyltransferase belonging to the UGT78 family, encoding flavonoid 3-O-glucosyltransferase (UF3GT), was cloned from the monocot species I. sanguinea. Compared with the control group, overexpression of IsUGT78 enhanced sensitivity to cadmium stress, while showing no significant impact under NaCl and d-sorbitol treatments. Under cadmium treatment, arabidopsis exogenously transformed with the IsUGT78 gene possessed lower germination, fresh weight, root length, and chlorophyll content and increased malondialdehyde content than the wild type arabidopsis. In addition, metabolomics in leaves led to the identification of 299 flavonoid metabolites, eight and 127 which were significantly up- and down-regulated, respectively, in the transgenic plants. Of note, all eight upregulated flavonoid compounds were glycosylated. Given that arabidopsis, which exogenously expresses the IsUGT78 gene, has reduced resistance to cadmium, IsUGT78 may lead to a reduced ability to cope with cadmium stress.

Evaluating long-term changes in precipitation resources is important for accurate hydrological evaluation and forecasting, water security and rational allocation of water resources. For this purpose in the Xinjiang Habahe area, tree-ring specimens were collected from Picea obovata, Larix sibirica, and Betula platyphylla to establish a tree-ring width chronology, which was used to analyse a correlation with the average temperature and precipitation per month for 1958–2016. Based on correlation coefficients for monthly temperature and precipitation with the chronology of tree-ring widths, radial tree growth was mainly restricted by precipitation, and tree-ring width chronology was significantly correlated with overall precipitation from the previous July to the next June (r = 0.641, P < 0.01). The above results were used to establish a transformation equation, and the overall precipitation from the previous July to the following June from 1800 to 2016 in Habahe was reconstructed after adjusted degrees of freedom, and obtain an explanatory rate of the variation up to 41.1% (40.0%). In addition to the reliability of the reconstructed values, the stability of the conversion function was determined via the “leave-one-out” method, which is commonly used in research on tree rings, and by cross-checking the conversion function with the reduced error value (RE), product mean test (t), with a sign test (ST). During the last 217 years, there were nine dry periods: 1803–1829, 1861–1865, 1872–1885, 1892–1905, 1916–1923, 1943–1954, 1961–1966, 1973–1981, and 2005–2011; and 12 wet periods: 1830–1834, 1836–1860, 1866–1871, 1886–1891, 1906–1915, 1925–1930, 1934–1942, 1955–1960, 1967–1972, 1982–1996, 2000–2004, and 2012–2016. Comparisons of the reconstructions for neighboring regions and a spatial correlation analysis showed that the reconstructed sequence of the present precipitation data better represented the changes in precipitation in Habahe. Additionally, a power spectrum analysis revealed that precipitation over the past 217 years in Habahe Province exhibited 2–5 years of quasiperiodic variation. A power spectrum analysis and wavelet analysis indicated that El Niño-Southern Oscillation influenced the precipitation cycles. This reconstruction provides more information on high-frequency precipitation, which is an important supplement to the existing tree-ring reconstruction of precipitation in the study area. The reconstruction of regional high-resolution precipitation changes over the last several hundred years provides unique, important data for understanding regional differences in climate at the decadal-centennial scale.

This paper introduces a new method of calculating crown projection area (CPA), the area of level ground covered by a vertical projection of a tree crown from measured crown radii through numerical interpolation and integration. This novel method and other four existing methods of calculating CPA were compared using detailed crown radius measurements from 30 tall trees of Eucalyptus pilularis variable in crown size, shape, and asymmetry. The four existing methods included the polygonal approach and three ways of calculating CPA as the area of a circle using the arithmetic, geometric and quadratic mean radius. Comparisons were made across a sequence of eight non-consecutive numbers (from 2 to 16) of measured crown radii for each tree over the range of crown asymmetry of the 30 trees through generalized linear models and multiple comparisons of means. The sequence covered the range of the number of crown radii measured for calculating the CPA of a tree in the literature. A crown asymmetry index within the unit interval was calculated for each tree to serve as a normative measure. With a slight overestimation of 2.2% on average and an overall mean error size of 7.9% across the numbers of crown radii that were compared, our new method was the least biased and most accurate. Calculating CPA as a circle using the quadratic mean crown radius was the second best, which had an average overestimation of 4.5% and overall mean error size of 8.8%. These two methods remained by and large unbiased as crown asymmetry increased, while the other three methods showed larger bias of underestimation. For the conventional method of using the arithmetic mean crown radius to calculate CPA as a circle, bias correction factors were developed as a function of crown asymmetry index to delineate the increasing magnitude of bias associated with greater degrees of crown asymmetry. This study reveals and demonstrates such relationships between the accuracy of CPA calculations and crown asymmetry and will help increase awareness among researchers and practitioners on the existence of bias in their CPA calculations and for the need to use an unbiased method in the future. Our new method is recommended for calculating CPA where at least four crown radius measurements per tree are available because that is the minimum number required for its use.

The combined use of LiDAR (Light Detection And Ranging) scanning and field inventories can provide spatially continuous wall-to-wall information on forest characteristics. This information can be used in many ways in forest mapping, scenario analyses, and forest management planning. This study aimed to find the optimal way to obtain continuous forest data for Catalonia when using kNN imputation (kNN stands for “k nearest neighbors”). In this method, data are imputed to a certain location from k field-measured sample plots, which are the most similar to the location in terms of LiDAR metrics and topographic variables. Weighted multidimensional Euclidean distance was used as the similarity measure. The study tested two different methods to optimize the distance measure. The first method optimized, in the first step, the set of LiDAR and topographic variables used in the measure, as well as the transformations of these variables. The weights of the selected variables were optimized in the second step. The other method optimized the variable set as well as their transformations and weights in one single step. The two-step method that first finds the variables and their transformations and subsequently optimizes their weights resulted in the best imputation results. In the study area, the use of three to five nearest neighbors was recommended. Altitude and latitude turned out to be the most important variables when assessing the similarity of two locations of Catalan forests in the context of kNN data imputation. The optimal distance measure always included both LiDAR metrics and topographic variables. The study showed that the optimal similarity measure may be different for different regions. Therefore, it was suggested that kNN data imputation should always be started with the optimization of the measure that is used to select the k nearest neighbors.

COVID-19 posed challenges for global tourism management. Changes in visitor temporal and spatial patterns and their associated determinants pre- and peri-pandemic in Canadian Rocky Mountain National Parks are analyzed. Data was collected through social media programming and analyzed using spatiotemporal analysis and a geographically weighted regression (GWR) model. Results highlight that COVID-19 significantly changed park visitation patterns. Visitors tended to explore more remote areas peri-pandemic. The GWR model also indicated distance to nearby trails was a significant influence on visitor density. Our results indicate that the pandemic influenced tourism temporal and spatial imbalance. This research presents a novel approach using combined social media big data which can be extended to the field of tourism management, and has important implications to manage visitor patterns and to allocate resources efficiently to satisfy multiple objectives of park management.

This study comprehensively assessed long-term vegetation changes and forest fragmentation dynamics in the Himalayan temperate region of Pakistan from 1989 to 2019. Four satellite images, including Landsat-5 TM and Landsat-8 Operational Land Imager (OLI), were chosen for subsequent assessments in October 1989, 2001, 2011 and 2019. The classified maps of 1989, 2001, 2011 and 2019 were created using the maximum likelihood classifier. Post-classification comparison showed an overall accuracy of 82.5% and a Kappa coefficient of 0.79 for the 2019 map. Results revealed a drastic decrease in closed-canopy and open-canopy forests by 117.4 and 271.6 km², respectively, and an increase in agriculture/farm cultivation by 1512.8 km². The two-way ANOVA test showed statistically significant differences in the area of various cover classes. Forest fragmentation was evaluated using the Landscape Fragmentation Tool (LFT v2.0) between 1989 and 2019. The large forest core (> 2.00 km²) decreased from 149.4 to 296.7 km², and a similar pattern was observed in medium forest core (1.00–2.00 km²) forests. On the contrary, the small core (< 1.00 km²) forest increased from 124.8 to 145.3 km² in 2019. The perforation area increased by 296.9 km², and the edge effect decreased from 458.9 to 431.7 km². The frequency of patches also increased by 119.1 km². The closed and open canopy classes showed a decreasing trend with an annual rate of 0.58% and 1.35%, respectively. The broad implications of these findings can be seen in the studied region as well as other global ecological areas. They serve as an imperative baseline for afforestation and reforestation operations, highlighting the urgent need for efficient management, conservation, and restoration efforts. Based on these findings, sustainable land-use policies may be put into place that support local livelihoods, protect ecosystem services, and conserve biodiversity.

Deciduous oaks (Quercus spp.) are distributed from subalpine to tropical regions in the northern hemisphere and have important roles as carbon sinks and in climate change mitigation. Determining variations in plant functional traits at multiple biological levels and linking them to environmental variables across geographical ranges is important for forecasting range-shifts of broadly-distributed species under climate change. We sampled leaves of five deciduous Quercus spp. covering approximately 20° of latitude (~ 21° N − 41° N) and 20 longitude (~ 99° E − 119° E) across China and measured 12 plant functional traits at different biological levels. The traits varied distinctively, either within each biological level or among different levels driven by climatic and edaphic variables. Traits at the organ level were significantly correlated with those at the cellular and tissue levels, while traits at the whole-plant level only correlated with those at the tissue level. The Quercus species responded to changing environments by regulating stomatal size, leaf thickness and the palisade mesophyll thickness to leaf thickness ratios with contrasting degree of effect to adjust the whole-plant functioning, i.e., intrinsic water use efficiency (iWUE), carbon supply and nitrogen availability. The results suggest that these deciduous Quercus spp. will maintain vigour by increasing iWUE when subjected to large temperature changes and insufficient moisture, and by accumulating leaf non-structural carbohydrates under drought conditions. The findings provide new insights into the inherent variation and trait coordination of widely distributed tree species in the context of climate change.

Long-term temperature variations inferred from high-resolution proxies provide an important context to evaluate the intensity of current warming. However, temperature reconstructions in humid southeastern China are scarce and particularly lack long-term data, limiting us to obtain a complete picture of regional temperature evolution. In this study, we present a well-verified reconstruction of winter-spring (January–April) minimum temperatures over southeastern China based on stable carbon isotopic (δ¹³C) records of tree rings from Taxus wallichiana var. mairei from 1860 to 2014. This reconstruction accounted for 56.4% of the total observed variance. Cold periods occurred during the 1860s–1910s and 1960s–1970s. Although temperatures have had an upward trend since the 1920s, most of the cold extremes were in recent decades. The El Niño-Southern Oscillation (ENSO) variance acted as a key modulator of regional winter-spring minimum temperature variability. However, teleconnections between them were a nonlinear process, i.e., a reduced or enhanced ENSO variance may result in a weakened or intensified temperature-ENSO relationship.

Anthropogenic disturbances are widespread in tropical forests and influence the species composition in the overstory. However, the impacts of historical disturbance on tropical forest overstory recovery are unclear due to a lack of disturbance data, and previous studies have focused on understory species. In this study, the purpose was to determine the influence of historical disturbance on the diversity, composition and regeneration of overstory species in present forests. In the 20-ha Xishuangbanna tropical seasonal rainforest dynamics plot in southwestern China, the historical disturbance boundaries were delineated based on panchromatic photographs from 1965. Factors that drove species clustering in the overstory layer (DBH ≥ 40 cm) were analyzed and the abundance, richness and composition of these species were compared among different tree groups based on multiple regression tree analysis. The coefficient of variation of the brightness value in historical panchromatic photographs from 1965 was the primary driver of species clustering in the overstory layer. The abundance and richness of overstory species throughout the regeneration process were similar, but species composition was always different. Although the proportion of large-seeded and vigorous-sprouting species showed no significant difference between disturbed and undisturbed forests in the treelet layer (DBH < 20 cm), the difference became significant when DBH increased. The findings highlight that historical disturbances have strong legacy effects on functional group composition in the overstory and the recovery of overstory species was multidimensional. Functional group composition can better indicate the dynamics of overstory species replacement during secondary succession.

Bushfires are devastating to forest managers, owners, residents, and the natural environment. Recent technological advances indicate a potential for faster response times in terms of detecting and suppressing fires. However, to date, all these technologies have been applied in isolation. This paper introduces the latest fire detection and suppression technologies from ground to space. An operations research method was used to assemble these technologies into a theoretical framework for fire detection and suppression. The framework harnesses the advantages of satellite-based, drone, sensor, and human reporting technologies as well as image processing and artificial intelligence machine learning. The study concludes that, if a system is designed to maximise the use of available technologies and carefully adopts them through complementary arrangements, a fire detection and resource suppression system can achieve the ultimate aim: to reduce the risk of fire hazards and the damage they may cause.

Global forests are increasingly crucial for achieving net-zero carbon emissions, with a quarter of the mitigation efforts under the Paris Climate Agreement directed towards forests. In China, forests currently contribute to 13% of the global land's carbon sink, but their stability and persistence remain uncertain. We examined and identified that published studies suffered from oversimplifications of ecosystem succession and tree demographic dynamics, as well as poor constraints on land quality. Consequently, substantial estimations might have been suffered from underrepresented or ignored crucial factors, including tree demographic dynamics, and disturbances and habitat shifts caused by global climate change. We argue that these essential factors should be considered to enhance the reliability and accuracy of assessments of the potential for forest carbon sinks.

Trees progress through various growth stages, each marked by specific responses and adaptation strategies to environmental conditions. Despite the importance of age-related growth responses on overall forest health and management policies, limited knowledge exists regarding age-related effects on dendroclimatic relationships in key subtropical tree species. In this study, we employed a dendrochronological method to examine the impact of rapid warming on growth dynamics and climatic sensitivity of young (40–60 years) and old (100–180 years) Pinus massoniana forests across six sites in central-southern China. The normalized log basal area increment of trees in both age groups increased significantly following rapid warming in 1984. Trees in young forests further showed a distinct growth decline during a prolonged severe drought (2004–2013), whereas those in old forests maintained growth increases. Tree growth was more strongly influenced by temperature than by moisture, particularly in old forests. Spring temperatures strongly and positively impacted the growth of old trees but had a weaker effect on young ones. Old forests had a significantly lower resistance to extreme drought but faster recovery compared to young forests. The “divergence problem” was more pronounced in younger forests due to their heightened sensitivity to warming-induced drought and heat stress. With ongoing warming, young forests also may initially experience a growth decline due to their heightened sensitivity to winter drought. Our findings underscore the importance of considering age-dependent changes in forest/tree growth response to warming in subtropical forest management, particularly in the context of achieving “Carbon Peak & Carbon Neutrality” goals in China.

Different chemical compositions of soil organic carbon (SOC) affect its persistence and whether it significantly differs between natural forests and plantations remains unclear. By synthesizing 234 observations of SOC chemical compositions, we evaluated global patterns of concentration, individual chemical composition (alkyl C, O-alkyl C, aromatic C, and carbonyl C), and their distribution evenness. Our results indicate a notably higher SOC, a markedly larger proportion of recalcitrant alkyl C, and lower easily decomposed carbonyl C proportion in natural forests. However, SOC chemical compositions were appreciably more evenly distributed in plantations. Based on the assumed conceptual index of SOC chemical composition evenness, we deduced that, compared to natural forests, plantations may have higher possible resistance to SOC decomposition under disturbances. In tropical regions, SOC levels, recalcitrant SOC chemical composition, and their distributed evenness were significantly higher in natural forests, indicating that SOC has higher chemical stability and possible resistance to decomposition. Climate factors had minor effects on alkyl C in forests globally, while they notably affected SOC chemical composition in tropical forests. This could contribute to the differences in chemical compositions and their distributed evenness between plantations and natural stands.

Forest disturbances at gap levels are one of the most important events for the regeneration and establishment of intermediate tree species. Abrupt canopy openings expose plants to high light intensity and high evaporative demands that stress shade-acclimated plants. Later, the slow closure of gaps reduces light availability to plants established when the incident irradiation was higher. This work evaluated the morphological and physiological acclimation of Cabralea canjerana (Vell) Mart. regeneration to sudden and to gradual changes in canopy cover. A pot experiment was carried out with plants exposed to a sudden opening. A few days after the light shock, plants rapidly increased photosynthetic rates and decreased leaf water potential. After two months, plants activated physiological responses at leaf and whole plant levels to high light and water stresses, e.g., increased stomatal conductance, stomatal index and reduction of leaf: fine roots ratio and chlorophyll. After seven months, hydraulic conductivity of petioles and the whole leaf increased, and growth was much higher than plants that remained under the canopy. In a field experiment in gaps in the rainforest, plants acclimated to all canopy covers. Seven years after planting, growth was maximum in open environments within the gaps, even if the canopy closed during the first 20 months after planting. In conclusion, if this species is planted to enrich the rainforest, positions within gaps with lower canopy cover should be chosen and gap closure will not affect growth. To manage C. canjerana natural regeneration, the opening of gaps and removal of understory will increase survival and growth without the risk that the stress caused by these sudden openings could lead to the death of seedlings. Combining pot and field experiments helps to understand the autecology of trees with particular ecological interest, and to build sound restoration practices.

Unstable environments intensify the frequency of extreme disasters. Long-term climate changes can lead to agricultural and ecological degradation that threatens population sustainability. To better understand past climatic events and consequences, here we present a reconstruction of the self-calibrating Palmer drought severity index (scPDSI) from September to August for the desert margins of northern China, dating back to 1742. The reconstruction accounts for 42.9% of the variation of meteorological data between 1951 and 2020. Our spatial correlation analyses showed significant correlations between scPDSI, runoff, and precipitation. Over the past 279 years, the study area has undergone nine dry and eight wet periods, with the most severe climate extremes between the 1850s and 1890s. This period of prolonged drought in northeastern China coincided with the combined impacts of climatic factors and human influences, contributing to the fall of the Qing Dynasty. Analysis of periodicity and anomalies in sea surface temperatures indicate a strong association between wet and dry cycles and El Niño-Southern Oscillations. Our findings offer insights into long-term dry and wet fluctuations at the desert margins in northern China and elucidate the relationship between drought and the dynamics of civilizations. They also highlight the potential impact of extremes in climate on modern society, especially under the four projected shared socioeconomic pathways climatic scenarios, which predict worsening droughts in northern China.

The use of mobile laser scanning to survey forest ecosystems is a promising, scalable technology to describe forest 3D structures at high resolution. To confirm the consistency in the retrieval of forest structural parameters using hand-held laser scanning (HLS), before operationalizing the method, confirming the data is crucial. We analyzed the performance of tree-level mapping based on HLS under different phenology conditions on a mixed forest in western Spain comprising Pinus pinaster and two deciduous species, Alnus glutinosa and Quercus pyrenaica. The area was surveyed twice during the growing season (July 2022) and once in the deciduous season (February 2022) using several scanning paths. Ground reference data (418 trees, 15 snags) was used to calibrate the HLS data and to assess the influence of phenology when converting 3D data into tree-level attributes (DBH, height and volume). The HLS-based workflow was robust at isolating tree positions and recognizing stems despite changes in phenology. Ninety-six percent of all pairs matched below 65 cm. For DBH, phenology barely altered estimates. We observed a strong agreement when comparing HLS-based tree height distributions. The values exceeded 2 m when comparing height measurements, confirming height data should be carefully used as reference in remote sensing-based inventories, especially for deciduous species. Tree volume was more precise for pines (r = 0.95, and relative RMSE = 21.3 –23.8%) compared to deciduous species (r = 0.91 –0.96, and relative RMSE = 27.3–30.5%). HLS data and the forest structural complexity tool performed remarkably, especially in tree positioning considering mixed forests and mixed phenology conditions.

Rapid increase in desertification is an environmental concern, especially for the health and sustainability of ecosystems in changing climates. How ecosystems respond to such changes may be partially understood by studying interactions and performance of critically important groups such as soil fungi functional groups. This study investigated variations in diversities of three soil fungi functional guilds (saprotrophic, symbiotic, pathogenic) and influencing abiotic factors in a Pinus densata forest on the southeast Tibetan Plateau where desertification is intense. The results indicate desertification significantly decreased the proportion of dominant fungal guild-symbiotic fungi (mean relative abundance decreasing from 97.0% to 68.3%), in contrast to saprotrophic fungi (increasing from 2.7% to 25.7%) and pathogenic (from 0.3% to 5.9%). Soil pH had the most significant impact on fungal community structure and negatively correlated with symbiotic fungal richness, which was significantly lower in arid soils, and positively correlated with saprotrophic and pathogenic fungal alpha-diversity, which were abundant. Different community structures and regulators of the three fungi communities were observed, with pH, total phosphorus and ammonium (NH₄ ⁺) as the main determinants. This study links the biotic and abiotic components during desertification and the interactions between them, and may be used as indicators of ecosystem health and for amendments to mitigate the effects of a changing climate.

Forest ecosystems within national parks are threatened by various biotic and abiotic factors. To determine the causes of the desiccation and death of trees in mixed coniferous and deciduous forests of Tara National Park (TNP), Serbia, we monitored defoliation and mortality of individual trees in permanent experimental plots. Data on the desiccation of a large number of trees were gathered by determining the total volume of dry trees and areas of forests under drying stress. The two sets of data were combined to determine the impact of climatic events, primarily drought periods, on the desiccation of forests. Combining data from the International Co-operative Program on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) with TNP data helped relate forest desiccation to climate events. Key climate signals were identified by monitoring tree defoliation changes in two permanent experimental plots, and then assessed for their influence on tree desiccation in the entire national park. The standardized precipitation evapotranspiration index (SPEI) was used for a more detailed analysis of the drought period. Despite the lack of climate data for a certain period, the SPEI index revealed a link between climate variables and the defoliation and desiccation of forests. Furthermore, the desiccation of trees was preceded by a long drought period. Although mixed coniferous-deciduous forests are often considered less vulnerable to natural influences, this study suggests that forest ecosystems can become vulnerable regardless of tree species composition due to multi-year droughts. These findings contribute to a better understanding of important clues for predicting possible future desiccation of forests. Continuous monitoring of the state of forests and of more permanent experimental plots in national parks could provide better quality data and timely responses to stressful situations.

In recent decades, the rapid climate warming in polar and alpine regions has been accompanied by an expansion of shrub vegetation. However, little is known about how changes in shrub distribution will change as the distribution of tree species and snow cover changes as temperatures rise. In this work, we analyzed the main environmental factors influencing the distribution and structure of Juniperus sibirica, the most common shrub species in the Southern Ural Mountains. Using mapping and digital elevation models, we demonstrated that J. sibirica forms a well-defined vegetation belt mainly between 1100 and 1400 m a.s.l. Within this zone, the abundance and cover of J. sibirica are influenced by factors such as rockiness, slope steepness, water regime and tree (Picea obovata) cover. An analysis of data spanning the past 9 years revealed an upward shift in the distribution of J. sibirica with a decrease in its area. The primary limiting factors for the distribution of J. sibirica were the removal of snow cover by strong winter winds and competition with trees. As a consequence of climatic changes, the tree line and forest limit have shifted upward, further restricting the distribution of J. sibirica to higher elevations where competition for light with trees is reduced and snow cover is sufficiently deep.

Investing in projects that support environmental benefits, such as tree harvesting, has the potential to reduce air pollution levels in the atmosphere in the future. However, this kind of investment may increase the current level of emissions. Therefore, it is necessary to estimate how much the policy affects the current level of CO₂ emissions. This makes sure the policy doesn’t increase the level of CO₂ emissions. This study aims to analyze the effect of the One Billion Trees program on CO₂ emissions in New Zealand by employing the 2020 input–output table analysis. This investigation examines the direct and indirect effects of policy on both the demand and supply sides across six regions of New Zealand. The results of this study for the first year of plantation suggest that the policy increases the level of CO₂ emissions in all regions, especially in the Waikato region. The direct and indirect impact of the policy leads to 64 kt of CO₂ emissions on the demand side and 270 kt of CO₂ emissions on the supply side. These lead to 0.19 and 0.74% of total CO₂ emissions being attributed to investment shocks. Continuing the policy is recommended, as it has a low effect on CO₂ emissions. However, it is crucial to prioritize the use of low-carbon machinery that uses fossil fuels during the plantation process.

In the context of ongoing climate change, relationships between tree growth and climate present uncertainties, which limits the predictions of future forest dynamics. Northwest China is a region undergoing notable warming and increased precipitation; how forests in this region will respond to climate change has not been fully understood. We used dendrochronological methods to examine the relationship between climate and the radial growth of four tree species in a riparian forest habitat in Altai region: European aspen (Populus tremula), bitter poplar (Populus laurifolia), Swedish birch (Betula pendula), and Siberian spruce (Picea obovata). The results reveal that European aspen was insensitive to climate changes. In contrast, bitter poplar showed a positive response to elevated temperatures and negative to increased moisture during the growing season. Swedish birch and Siberian spruce were adversely affected by higher temperatures but benefited from increased precipitation. A moving correlation analysis suggested that, against a backdrop of continuous warming, growth patterns of these species will diverge: European aspen will require close monitoring, bitter poplar may likely to show accelerated growth, and the growth of Swedish birch and Siberian spruce may be inhibited, leading to a decline. These findings offer insight into the future dynamics of riparian forests under changing climate.

In recent years, the situation of the Hyphantria cunea (Drury) (Lepidoptera: Erebidae), infestation in China has been serious and has a tendency to continue to spread. A comprehensive analysis was carried out to examine the spatial distribution trends and influencing factors of H. cunea. This analysis involved integrating administrative division and boundary data, distribution data of H. cunea, and environmental variables for 2021. GeoDetector and gravity analysis techniques were employed for data processing and interpretation. The results show that H. cunea exhibited high aggregation patterns in 2021 and 2022 concentrated mainly in eastern China. During these years, the focal point of the infestation was in Shandong Province with a spread towards the northeast. Conditions such as high vegetation density in eastern China provided favorable situations for growth and development of H. cunea. In China, the spatial distribution of the moth is primarily influenced by two critical factors: precipitation during the driest month and elevation. These play a pivotal role in determining the spread of the species. Based on these results, suggestions are provided for a multifaceted approach to prevention and control of H. cunea infestation.

The addition of ectomycorrhizal fungi (ECMF), beneficial rhizosphere microorganisms, to the soil can promote plant growth and resistance. Here, Populus davidiana ×  Populus bolleana tissue culture seedlings were grown for 3 months in soils inoculated with one of the species, then seedlings were assessed for mycorrhizal colonization rate and growth, physiological and root traits. Suillus luteus and Populus involutus each formed ectomycorrhizal associations with the seedlings. Seedling height, ground diameter, biomass, and leaf area were significantly greater after treatment with ECMF than in the non-inoculated controls. Treatment improved all physiological and root variables assessed (chlorophylls and carotenoids, cellulose, and soluble sugars and proteins; root length, surface area, projected area, mean diameter, volume, number of root tips). Seedlings inoculated with S. luteus outperformed those inoculated with P. involutus.

Under global warming, drought will reduce productivity of Pinus halepensis s.l. (subspecies halepensis and brutia) and cause a retreat from its rear edge distribution (latitudinal/elevational) in the Mediterranean. To test whether topography can influence this scenario, we studied for approximately 40 years the growth of six natural pine stands in water-limited habitats on the islands of Zakinthos and Samos (eastern Mediterranean Greece), and determined the critical moisture sources that drove pine growth. Dominant pines were selected with no permanent water sources under contrasting moisture conditions created by topography (“wet”-gulley/valley vs. “dry”-upslope habitats). The responses of P. halepensis s.l. to drought under a moderate and a worst case scenario were tested, projected under global warming (approx. − 25% and 40% in annual precipitation compared to 1961–1990 average). Our results show that “wet” habitat pines had higher productivity under normal to wet climate. However, the more precipitation declined, “wet” habitat tree growth was reduced at a significantly faster rate, but also showed a faster recovery, once rainfall returned. Thus, Pinus halepensis s.l. populations in gullies/valleys, may be more drought resilient and less likely to retreat towards higher elevation/latitudes under global warming, compared to pines on dry upslope sites. Under moderate drought, both ecosystems relied on deeper moisture pools supplied by rainfall of the previous 3–6 years (including the year of growth). However, valley/gully habitat pines on significantly deeper soils (and probably on deeper heavily weathered bedrock), appeared to utilize surface moisture from winter/spring rainfall more efficiently for survival and recovery. Thus, deep soils may provide the key “buffer” for pine survival in such ecosystems that could act as potential refugia for P. halepensis s.l. under climate change.

Ecoregion-based height-diameter models were developed in the present study for Scots pine (Pinus sylvestris L.) stands in Turkiye and included several ecological factors derived from a pre-existing ecoregional classification system. The data were obtained from 2831 sample trees in 292 sample plots. Ten generalized height–diameter models were developed, and the best model (HD10) was selected according to statistical criteria. Then, nonlinear mixed-effects modeling was applied to the best model. The R ² for the generalized height‒diameter model (Richards function) modified by Sharma and Parton is 0.951, and the final model included number of trees, dominant height, and diameter at breast height, with a random parameter associated with each ecoregion attached to the inverse of the mean basal area. The full model predictions using the nonlinear mixed-effects model and the reduced model (HD10) predictions were compared using the nonlinear sum of extra squares test, which revealed significant differences between ecoregions; ecoregion-based height–diameter models were thus found to be suitable to use. In addition, using these models in appropriate ecoregions was very important for achieving reliable predictions with low prediction errors.

In northern China, light and temperature are major limiting factors for plant growth, particularly during seed production and seedling establishment. While previous studies suggested a possible role for the MYB97 gene in cold-stress, confirmation through documented evidence was lacking. In this study, we transformed the MYB97 gene from Iris laevigata into tobacco, and discovered that the gene boosted photosynthesis, photoprotection and resilience to cold. The transgenic tobacco seeds exhibited enhanced germination and accelerated seedling growth. Moreover, these plants had decreased levels of MDA (Malondialdehyde) and relative conductance, coupled with elevated concentrations of proline and soluble sugars. This response was accompanied by heightened activity of antioxidant enzymes during periods of cold stress (4 and − 2 °C). Exposure to low temperatures (0–15 °C) also reduced heights but accentuated primary root growth in transgenic tobacco plants. Additionally, tobacco leaves showed an increased growth along with higher chlorophyll levels, net photosynthetic rates, stomatal conductance, transpiration rates and non-photochemical quenching coefficient. This study shows that IlMYB97 (The MYB97 genes in I. laevigata) improves cold-resistance, and enhances photosynthesis and photoprotective ability, and thus overall growth and development. These findings would offer the genetic resources to further study cold resistance and photosynthesis.

Plant stoichiometry and nutrient allocation may reflect adaptation strategies to environmental nutrient changes. Fire, as a major disturbance in forests, mediates soil nutrient availability that may influence plant nutrient dynamics. However, plant–soil stoichiometric allocation strategies during different post-fire periods and the effects of soil, enzymes, and microbial biomass on plant stoichiometry are largely unknown. The pioneer tree species Betula platyphylla in burnt forests of northern China was the object of this study, and severely burned areas selected with different fire years. Nearby unburned areas acted as a control. Carbon (C), nitrogen (N), and phosphorus (P) contents in leaves, branches, and fine roots and rhizosphere soil, C-, N- and P-acquiring enzyme activities were examined. Microbial biomass C, N, and P were measured, and factors influencing C:N:P stoichiometry of plants during the burned area restoration were explored. Our results show that C and N contents in leaves increased with time since fire, while C and P in branches and C, N and P in fine roots decreased. Activities of C-, N-, and P-acquiring enzymes and microbial biomass N increased with time since fire. Redundancy analysis showed that changes in soil N-acquiring enzyme activity, microbial biomass C, and N had significant effects on plant ecological stoichiometry. These results show a significant flexibility in plant nutrient element allocation strategies and C:N:P stoichiometric characteristics. Soil extracellular enzyme activity drives the changes in stoichiometry during the process of post-fire restoration.

Annual tree rings are widely recognized as valuable tools for quantifying and reconstructing historical forest disturbances. However, the influence of climate can complicate the detection of disturbance signals, leading to limited accuracy in existing methods. In this study, we propose a random under-sampling boosting (RUB) classifier that integrates both tree-ring and climate variables to enhance the detection of forest insect outbreaks. The study focused on 32 sites in Alberta, Canada, which documented insect outbreaks from 1939 to 2010. Through thorough feature engineering, model development, and tenfold cross-validation, multiple machine learning (ML) models were constructed. These models used ring width indices (RWIs) and climate variables within an 11-year window as input features, with outbreak and non-outbreak occurrences as the corresponding output variables. Our results reveal that the RUB model consistently demonstrated superior overall performance and stability, with an accuracy of 88.1%, which surpassed that of the other ML models. In addition, the relative importance of the feature variables followed the order RWIs > mean maximum temperature (T _max) from May to July > mean total precipitation (P _mean) in July > mean minimum temperature (T _min) in October. More importantly, the dfoliatR (an R package for detecting insect defoliation) and curve intervention detection methods were inferior to the RUB model. Our findings underscore that integrating tree-ring width and climate variables as predictors in machine learning offers a promising avenue for enhancing the accuracy of detecting forest insect outbreaks.

The reverse J-shaped diameter distribution is considered an inherent attribute of natural forests, crucial for forest resource utilization and community stability. However, in karst regions, intense habitat heterogeneity might alter species composition, spatial distribution, growth, biomass allocation, and mortality processes, yet its impact on diameter structure remains unclear. A fixed plot of 200 m × 110 m was established in the Nanpan River Basin, Southwest China, within an old-growth oak forest (> 300 years old), and the influence of site substrates (i.e., rock and soil), topographic factors, sample area, and orientation on diameter distribution was analyzed. Trees on both rock and soil exhibited a reverse-J shape, quantifiable through the Weibull function. The substrates had a similar density, approximately 2100 plants/ha. However, the average and range of diameter of trees on rock were smaller than those on soil, suggesting that rock constrains tree growth. The diameter distribution of trees across microtopography also displayed a reverse-J shape. Yet, higher elevations and sunny slopes showed a greater curvature of diameter classes compared to lower elevations and shady slopes, indicating habitat preferences in karst trees. Sample area and orientation had minimal effects on diameter class curve that reached stability when the plot size was 6000 m². These results suggest that the reverse J-shaped diameter distribution prevails at small scales in karst old-growth forests, encompassing multiple curvatures and spanning forest ecosystems.

The rate of fire spread is a key indicator for assessing forest fire risk and developing fire management plans. The Rothermel model is the most widely used fire spread model, established through laboratory experiments on homogeneous fuels but has not been validated for conifer-deciduous mixed fuel. In this study, Pinus koraiensis and Quercus mongolica litter was used in a laboratory burning experiment to simulate surface fire spread in the field. The effects of fuel moisture content, mixed fuel ratio and slope on spread rate were analyzed. The optimum packing ratio, moisture-damping coefficient and slope parameters in the Rothermel model were modified using the measured spread rate which was positively correlated with slope and negatively with fuel moisture content. As the Q. mongolica load increased, the spread rate increased and was highest at a fuel ratio of 4:6. The model with modified optimal packing ratio and slope parameters has a significantly lower spread rate prediction error than the unmodified model. The spread rate prediction accuracy was significantly improved after modifying the model parameters based on spread rates from laboratory burning simulations.

Pine wood nematode infection is a devastating disease. Unmanned aerial vehicle (UAV) remote sensing enables timely and precise monitoring. However, UAV aerial images are challenged by small target size and complex surface backgrounds which hinder their effectiveness in monitoring. To address these challenges, based on the analysis and optimization of UAV remote sensing images, this study developed a spatio-temporal multi-scale fusion algorithm for disease detection. The multi-head, self-attention mechanism is incorporated to address the issue of excessive features generated by complex surface backgrounds in UAV images. This enables adaptive feature control to suppress redundant information and boost the model’s feature extraction capabilities. The SPD-Conv module was introduced to address the problem of loss of small target feature information during feature extraction, enhancing the preservation of key features. Additionally, the gather-and-distribute mechanism was implemented to augment the model’s multi-scale feature fusion capacity, preventing the loss of local details during fusion and enriching small target feature information. This study established a dataset of pine wood nematode disease in the Huangshan area using DJI (DJ-Innovations) UAVs. The results show that the accuracy of the proposed model with spatio-temporal multi-scale fusion reached 78.5%, 6.6% higher than that of the benchmark model. Building upon the timeliness and flexibility of UAV remote sensing, the proposed model effectively addressed the challenges of detecting small and medium-size targets in complex backgrounds, thereby enhancing the detection efficiency for pine wood nematode disease. This facilitates early preemptive preservation of diseased trees, augments the overall monitoring proficiency of pine wood nematode diseases, and supplies technical aid for proficient monitoring.

Typhoons are becoming frequent and intense with ongoing climate change, threatening ecological security and healthy forest development in coastal areas. Eucalyptus of a predominant introduced species in southern China, faces significant growth challenges because of typhoon. Therefore, it is vital to investigate the variation of related traits and select superior breeding materials for genetic improvement. Variance, genetic parameter, and correlation analyses were carried out on wind damage indices and eight wood properties in 88 families from 11 provenances of 10-year-old Eucalyptus camaldulensis. The selection index equation was used for evaluating multiple traits and selecting superior provenances and family lines as future breeding material. The results show that all traits were highly significantly different at provenance and family levels, with the wind damage index having the highest coefficient of genetic variation. The heritability of each trait ranged from 0.48 to 0.87, with the wind damage index, lignin and hemicellulose contents, and microfibril angle having the highest heritabilities. The wind damage index had a positive genetic correlation with wood density, a negative correlation with lignin content, a negative phenotypic correlation and a negative genetic correlation with microfibril angle. Wind damage index and genetic progress in the selection of eight wood traits varied from 7.2% to 614.8%. Three provenances and 12 superior families were selected. The genetic gains of the wind damage index were 10.2% and 33.9% for provenances and families, and these may be starting material for genetic modification for wind resistance in eucalyptus and for their dissemination to typhoon-prone coastal areas of southern China.

Effective breeding requires multiplying desired genotypes, keeping them at a convenient location to perform crosses more efficiently, and building orchards to generate material for reforestation. While some of these aims can be achieved by conventional grafting involving only rootstock and scion, topgrafting is known to deliver all in a shorter time span. In this study, Scots pine scions were grafted onto the upper and lower tree crowns in two clonal archives with the aim of inducing early female and male strobili production, respectively. Their survival rates and strobili production were analyzed with generalized linear mixed models. Survival was low (14%) to moderate (41%), and mainly affected by the topgraft genotype, interstock genotype, crown position and weather conditions in connection with the grafting procedure. Survival was not affected by the cardinal position in the crown (south or north). Male flowering was ample three years after grafting and reached 56% in the first year among live scions, increasing to 62 and 59% in consecutive years. Female flowering was scarce and was 9% at first, later increasing to 26 and 20% of living scions but was strongly affected by the topgraft genotype. In one subset of scions, female flowering was observed 1 year after grafting. Overall, flowering success was mainly affected by the topgraft and interstock genotypes, and secondary growth of scions. This is one of few reports on topgrafting in functional Scots pine clonal archives.

Cold stress severely limits the distribution of mangrove species worldwide and it remains unclear how mangroves respond and adapt to cold temperatures. In this study, we investigated the effects of cold acclimation and/or inhibition of serotonin levels on reactive oxygen species (ROS), reactive nitrogen species (RNS), melatonin (MEL) and serotonin (SER) accumulation during cold stress in Kandelia obovata. Morphologic observation and parameter analysis revealed that cold acclimation mitigated the photoinhibition of photosystem I (PSI) and photosystem II (PSII), maintained optimal ROS and RNS redox homeostasis, and increased the contents of SER and MEL in leaves. This suggests that cold acclimation reshapes the MEL/ROS/RNS redox network. In particular, the tryptophan/tryptamine/Ser/N-acetylserotonin/MER pathway was identified as a branch of the MEL synthesis pathway. Inhibition of endogenous SER exacerbated damage caused by cold stress, indicating the crosstalk of SER synthesis and cold acclimation. In this study, we report a coordinated regulation of cold stress by a complex defense network in K. obovata.

Plant carbon (C) concentration is a fundamental trait for estimating C storage and nutrient utilization. However, the mechanisms of C concentration variations among different tree tissues and across species remains poorly understood. In this study, we explored the variations and determinants of C concentration of nine tissues from 216 individuals of 32 tree species, with particular attention on the effect of wood porosity (i.e., non-porous wood, diffuse-porous wood, and ring-porous wood). The inter-tissue pattern of C concentration diverged across the three porosity types; metabolically active tissues (foliage and fine roots, except for the foliage of ring-porous species) generally had higher C levels compared with inactive wood. The poor inter-correlations between tissue C concentrations indicated a necessity of measuring tissue- and specific-C concentrations. Carbon concentration for almost all tissues generally decreased from non-porous, to diffuse-porous and to ring-porous. Tissue C was often positively correlated with tissue (foliage and wood) density and tree size, while negatively correlated with growth rate, depending on wood porosity. Our results highlight the mediating effect of type of wood porosity on the variation in tissue C among temperate species. The variations among tissues were more important than that among species. These findings provided insights on tissue C concentration variability of temperate forest species.

To study the effect of thinning intensity on the carbon sequestration by natural mixed coniferous and broadleaf forests in Xiaoxing’an Mountains, China, we established six 100 m × 100 m experimental plots in Dongfanghong Forest that varied in thinning intensity: plot A (10%), B (15%), C (20%), D (25%), E (30%), F (35%), and the control sample area (0%). A principal component analysis was performed using 50 different variables, including species diversity, soil fertility, litter characteristics, canopy structure parameters, and seedling regeneration parameters. The effects of thinning intensity on carbon sequestration were strongest in plot E (0.75), followed by D (0.63), F (0.50), C (0.48), B (0.22), A (0.11), and the control (0.06). The composite score of plot E was the highest, indicating that the carbon sequestration effect was strongest at a thinning intensity of 30%. These findings provide useful insights that could aid the management of natural mixed coniferous and broadleaf forests in Xiaoxing’an Mountains, China. This information has implications for future studies of these forests, and the methods used could aid future ecological assessments of the natural forests in Xiaoxing’an Mountains, China.

Recent advances in spectral sensing techniques and machine learning (ML) methods have enabled the estimation of plant physiochemical traits. Nitrogen (N) is a primary limiting factor for terrestrial forest growth, but traditional methods for N determination are labor-intensive, time-consuming, and destructive. In this study, we present a rapid, non-destructive method to predict leaf N concentration (LNC) in Metasequoia glyptostroboides plantations under N and phosphorus (P) fertilization using ML techniques and unmanned aerial vehicle (UAV)- based RGB (red, green, blue) images. Nine spectral vegetation indices (VIs) were extracted from the RGB images. The spectral reflectance and VIs were used as input features to construct models for estimating LNC based on support vector machine, random forest (RF), and multiple linear regression, gradient boosting regression and classification and regression trees (CART). The results show that RF is the best fitting model for estimating LNC with a coefficient of determination (R ²) of 0.73. Using this model, we evaluated the effects of N and P treatments on LNC and found a significant increase with N and a decrease with P. Height, diameter at breast height (DBH), and crown width of all M. glyptostroboides were analyzed by Pearson correlation with the predicted LNC. DBH was significantly correlated with LNC under N treatment. Our results highlight the potential of combining UAV RGB images with an ML algorithm as an efficient, scalable, and cost-effective method for LNC quantification. Future research can extend this approach to different tree species and different plant traits, paving the way for large-scale, time-efficient plant growth monitoring.

Urban and community forestry is a specialized discipline focused on the meticulous management of trees and forests within urban, suburban, and town environments. This field often entails extensive civic involvement and collaborative partnerships with institutions. Its overarching objectives span a spectrum from preserving water quality, habitat, and biodiversity to mitigating the Urban Heat Island (UHI) effect. The UHI phenomenon, characterized by notably higher temperatures in urban areas compared to rural counterparts due to heat absorption by urban infrastructure and limited urban forest coverage, serves as a focal point in this study. The study focuses on developing a methodological framework that integrates Geographically Weighted Regression (GWR), Random Forest (RF), and Suitability Analysis to assess the Urban Heat Island (UHI) effect across different urban zones, aiming to identify areas with varying levels of UHI impact. The framework is designed to assist urban planners and designers in understanding the spatial distribution of UHI and identifying areas where urban forestry initiatives can be strategically implemented to mitigate its effect. Conducted in various London areas, the research provides a comprehensive analysis of the intricate relationship between urban and community forestry and UHI. By mapping the spatial variability of UHI, the framework offers a novel approach to enhancing urban environmental design and advancing urban forestry studies. The study’s findings are expected to provide valuable insights for urban planners and policymakers, aiding in creating healthier and more livable urban environments through informed decision-making in urban forestry management.

Available water for communities is insufficient in the central part of Myanmar due to limited rainfall and surface water resources. Over the last two decades, afforestation and reforestation projects have been implemented in this region to provide sufficient water to local communities, expecting forested areas to store more rainwater than other land uses. However, there has been no research and very limited information on rainfall partitioning into throughfall (TF) and stemflow (SF), particularly concerning tree characters. Gross rainfall, TF under different canopy types, and SF of different tree types were measured in 2019. TF and SF were frequently observed even without rain but under foggy conditions. Therefore, both were partitioned into TF and SF from rainfall and fog individually. Sparser canopies resulted in larger TF from rainfall than denser canopies. However, a denser canopy delivered larger TF from fog than a sparser one. TF rates from rainfall in sparser and denser canopies were 54.5% and 51.5%, respectively, while those from fog were 15.2% and 27.2%, respectively. As a result, total TF rate in the denser canopy (70.7%) was significantly larger than that from the sparser one (64.3%). Short trees with small crown projection area and smooth bark (Type I) resulted in larger SF from rainfall than taller trees with large crown projection area and rough bark (Type II). However, Type II trees resulted in larger SF from fog. SF rates by rainfall from Type I and II trees were 17.5% and 12.2%, respectively, while those by fog were 22.2% and 39.5%, respectively. No significant total SF rates were found for Type I (22.5%) and II trees (20.1%). A denser canopy results in larger TF, and Type I trees result in larger SF. In an area where foggy conditions occur frequently and for a lengthy period, however, Type II trees will result in larger SF. These three tree characters (dense canopies, short trees with small crown projection area and smooth bark, and tall trees with large crown projection area and rough bark) should be considered for afforestation and reforestation projects in the Popa Mountain Park to enhance net water input by forests.

Stand age is an important indicator of tree growth and life cycle, and has implications for ecological and biological processes. This study examined changes in soil microbial biomass (SMB) as well as enzyme activities of different aged plantations and revealed their relationship to soil properties. SMB, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorous (MBP) and enzyme activities (β-1,4-glucosidase (β-G), β-1,4-xylosidase (β-X), cellobiohydrolase (CBH), leucine aminopeptidase (LAP), β-1,4-n-acetylglucosamine (NAG) and acid phosphatase (ACP)) were measured in Oromosia hosiei plantations of different ages. The soil quality index (SQI) model assessed soil quality. SMB contents significantly decreased in young (7-year-old) and mature plantations (45-year-old) compared to middle-aged (20-year-old) plantations. Activity of soil β-G, β-X, CBH and NAG in the 20-year-old plantations was markedly higher than in the other plantations except for β-G, CBH and NAG in the 45-year-old plantations. Soil organic carbon (SOC), total potassium (TK), total porosity, dissolved organic carbon, nitrate nitrogen (NO₃ ⁻-N) and non-capillary porosity were key factors affecting SMB, while soil bulk density, pH, SOC, NO₃ ⁻-N, TK and forest litter (FL) were the main factors affecting soil enzyme activities. SQI decreased in the order: middle-aged > mature > young. The efficiency of soil organic matter conversion, the effect of nitrogen mineralization and fixation by microorganisms, and the better efficiency of phosphorus utilization in mid-age plantations, which improves soil physical properties, better facilitates tree growth, and further improves the buffering of the soil against acidity and alkalinity. FL quality was the only soil biological factor affecting soil enzyme activity. Our findings demonstrate that different aged plantations affect soil microbial biomass, enzyme activity, and soil quality.

The most important process before leaf senescence is nutrient resorption, which reduces nutrient loss and maximizes plant fitness during the subsequent growth period. However, plants must retain certain levels of nitrogen (N) in their leaves to maintain carbon assimilation during hardening. The objective of this study was to investigate the tradeoffs in N investment between leaf N resorption and N for photosynthesis in seedlings with increased soil fertility during the hardening period. A field experiment was conducted to determine if and how soil fertility treatments (17, 34, or 68 mg N seedling⁻¹) affected N resorption and allocation to the photosynthetic apparatus in Quercus mongolica leaves during the hardening period. Seedlings were sampled at T₁ (after terminal bud formation), T₂ (between terminal bud formation and end of the growing period), and T₃ (at the end of the growing period). Results showed that photosynthetic N content continued to rise in T₂, while N resorption started from non-photosynthetic N. Leaf N allocation to the photosynthetic apparatus increased as soil fertility increased, delaying N resorption. Additionally, soil fertility significantly affected N partitioning among different photosynthetic components, maintaining or increasing photosynthetic traits during senescence. This study demonstrates a tradeoff in N investment between resorption and photosynthesis to maintain photosynthetic assimilation capacity during the hardening period, and that soil fertility impacts this balance. Q. mongolica leaves primarily resorbed N from the non-photosynthetic apparatus and invested it in the photosynthetic apparatus, whereas different photosynthetic N component allocations effectively improved this pattern.

The spatial pattern of trees is an important feature of forests, and different spatial patterns of trees exhibit different ecological stability. Research has confirmed that natural forests with random patterns have higher biodiversity and stronger resistance to unstable factors such as pests and diseases. Even if they are disturbed or destroyed by unstable factors such as pests and diseases, they can still recover and rescue themselves; while artificial forests with uniform and clustered patterns have lower biodiversity and are susceptible to unstable factors such as pests and diseases. And once pests and diseases occur, it’s more difficult for them to recover. In order to promote the healthy and stable development of the forestry industry and protect the diversity of the biological environment, it is necessary to protect the random pattern of natural forests from being destroyed in the process of forest management, while effectively transforming the spatial pattern of artificial forests into a random pattern. Therefore, in order to ensure the convenient and accurate determination of the type of forest spatial pattern, research on methods for determining forest spatial pattern has become particularly important. Based on the theory of uniformity, this study proposes definitions and related theories of included exclusive sphere, included exclusive body, included random pattern, and included uniformity. Under the guidance of the definition of inclusion uniformity and related theories, and by using mathematical method, it is proved that the uniformity of inclusion (CL) is asymptotically subject to the Eq. 18, Therefore, the relationship between the included uniformity (CL) and the number of trees in the sample plot was established, and the corresponding relationship formula was obtained, and then the determination of the spatial pattern type of trees was completed by using the corresponding relationship formula. Through rigorous reasoning and case verification, the determination method of forest spatial pattern is effective.

A decline in tree growth has occurred in numerous regions over recent decades and is associated with enhanced water deficits driven by climate warming. This phenomenon may be more noticeable at lower latitudes with higher temperatures. However, the process by which these elevated temperatures alter growth performance is not well understood. In this study, by combining tree-ring data (including 340 increment cores) and remotely sensed vegetation index data, we investigated the long-term growth performance of Pinus sylvestris var. mongolica Litv. (Mongolian pine), an important species for afforestation in northern China, in response to environmental factors in an area of introduction (lower latitude) and its native range (higher latitude). More notable decreases in both tree-ring width index (RWI) and basal area increment at breast height coincided with lower values and larger variations in the satellite-derived vegetation index in the area of introduction. The RWI showed stronger negative correlations with temperature and positive correlations with the self-calibrating Palmer drought severity index during most months in the introduction area. These results indicate that enhanced drought stress caused by elevated temperatures in lower latitudes might be a key factor for the growth decline in Mongolian pine plantations. The negative impact of increased temperatures on tree growth through exacerbating drought stress at lower latitudes with water deficit highlights the need to reduce water stress in forest management in such areas under climate warming-driven aridification.

Glutathione-S-transferase (GST, EC2.5.1.18) multifunctional protease is important for detoxification, defense against biotic and abiotic stresses, and secondary metabolic material transport for plant growth and development. In this study, 71 members of the BpGST family were identified from the entire Betula platyphylla Suk. genome. Most of the members encode proteins with amino acid lengths ranging from 101 to 875 and were localized to the cytoplasm by a prediction. BpGSTs can be divided into seven subfamilies, with a majority of birch U and F subfamily members according to gene structure, conserved motifs and evolutionary analysis. GST family genes showed collinearity with 22 genes in Oryza sativa L., and three genes in Arabidopsis thaliana; promoter cis-acting elements predicted that the GST gene family is functional in growth, hormone regulation, and abiotic stress response. Most members of the F subfamily of GST (BpGSTFs) were expressed in roots, stems, leaves, and petioles, with the most expression observed in leaves. On the basis of the expression profiles of F subfamily genes (BpGSTF1 to BpGSTF13) during salt, mannitol and ABA stress, BpGSTF proteins seem to have multiple functions depending on the type of abiotic stress; for instance, BpGSTs may function at different times during abiotic stress. This study enhances understanding of the GST gene family and provides a basis for further exploration of their function in birch.

Acorn production in oaks (Quercus spp.) shows considerable inter-annual variation, known as masting. The effects of pollen sourced from trees within or outside the stand on acorn production were investigated in pedunculate oak (Quercus robur L.) in an ancient mixed woodland during two moderate masting years. Comparisons were made between natural pollination, hand pollinations with out-of-stand pollen, in-stand pollen or a 1:1 combination of the two pollen sources, and for bagged flowers left unpollinated. After all treatments, > 85% of the flowers or developing acorns were aborted between May and August of both years. When flowers were protected with pollen bags and no pollen added, no acorns were produced. In contrast, hand pollination with out-of-stand pollen produced the most acorns both years and significantly more than within-stand pollen or natural pollination in 2022. Hand pollination with out-of-stand or within-stand pollen provided significantly more acorns than natural pollination in 2023. In 2022, hand pollination with a 1:1 mixture of out-of-stand and within-stand pollen yielded an intermediate number of mature acorns between those for the out-of-stand and within-stand pollination treatments. The study provides clear evidence of maternal choice during acorn development in pedunculate oak and of the benefits of pollen supplementation. It also confirms that pedunculate oak is a fruit-maturation masting species; abortion of pollinated flowers and immature acorns determines a mast year (rather than the number of flowers produced) at this site.

Although numerous studies have proposed explanations for the specific and relative effects of stand structure, plant diversity, and environmental conditions on carbon (C) storage in forest ecosystems, understanding how these factors collectively affect C storage in different community layers (trees, shrubs, and herbs) and forest types (mixed, broad-leaved (E), broad-leaved (M), and coniferous forest) continues to pose challenges. To address this, we used structural equation models to quantify the influence of biotic factors (mean DBH, mean height, maximum height, stem density, and basal area) and abiotic factors (elevation and canopy openness), as well as metrics of species diversity (Shannon–Wiener index, Simpson index, and Pielou’s evenness) in various forest types. Our analysis revealed the critical roles of forest types and elevation in explaining a substantial portion of variability in C storage in the overstory layer, with a moderate influence of stand factors (mean DBH and basal area) and a slightly negative impact of tree species diversity (Shannon–Wiener index). Notably, forest height emerged as the primary predictor of C storage in the herb layer. Regression relationships further highlighted the significant contribution of tree species diversity to mean height, understory C storage, and branch biomass within the forest ecosystem. Our insights into tree species diversity, derived from structural equation modeling of C storage in the overstory, suggest that the effects of tree species diversity may be influenced by stem biomass in statistical reasoning within temperate forests. Further research should also integrate tree species diversity with tree components biomass, forest mean height, understory C, and canopy openness to understand complex relationships and maintain healthy and sustainable ecosystems in the face of global climate challenges.

Understanding why elements are distributed in tree xylem in a particular way is a significant challenge in dendrochemistry. This study explored a hypothesis that metal elements in the xylem interact due to differences in physical properties such as ionic radius and ionization potential. Scots pine in an even-aged stand established during the early 1970s in eastern Siberia was the study species. Increment cores were taken from the north and south sides of trees and scanned with an X-ray fluorescent multi scanner. With the help of X-ray scanning, the following elements were analyzed: aluminum (Al), potassium (K), calcium (Ca), titanium (Ti), manganese (Mn), iron (Fe), copper (Cu), strontium (Sr) and zinc (Zn). Scanning data on the elements were split into early-wood and late-wood data for each year of growth. The following ratios were analyzed: Ca/Sr, Fe/Ca, Fe/Sr, Al/Cu, Al/Zn, Ti/Mn, and Mn/K. Among these, ones having a consistent pattern across tree rings, the ratios show a more or less dependable relationship: that an element shows a larger decrease (relative another element) that has a larger ionic radius and lower ionization potential. Hypothetically, this may be due to the advantage of an ion with smaller ionic radius and higher ionization potential under a deficit of accommodation centers in organic molecules. An experiment approach should be applied to clarify the relationships.

Based on the survey data of nine primitive broad-leaved Korean pine forest plots ranging from 1 to 10.4 ha in Heilongjiang Province, this study used the moving window method and GIS technology to analyze the variation characteristics of the spatial distribution pattern of forest biomass in each plot. We explored the minimum area that can reflect the structural and functional characteristics of the primitive broad-leaved Korean pine forest, and used computer simulation random sampling method to verify the accuracy of the minimum area. The results showed that: (1) Through the analysis of the spatial distribution raster map of biomass deviation in the plots at various scales of 10 − 100 m, there is a minimum area (0.64 ha) for the critical range of biomass density variation in the primitive broad-leaved Korean pine forest. This minimum area based on biomass density can indirectly reflect the comprehensive characteristics of productivity level per unit area, structure, function, and environmental quality of the primitive broad-leaved Korean pine forest community. (2) Using computer simulation random sampling, it was found that only by sampling in a specific plot larger than or equal to the minimum area can equivalent or similar results be achieved as random sampling within the plot, indicating that the minimum area determined by the moving window method is accurate. (3) The minimum area determined in this paper is an excellent indicator reflecting the complexity of community structure, which can be used for comparing changes in community structure and function before and after external disturbances, and has a good evaluation effect. This minimum area can also be used as a basis for scientific and reasonable setting of plot size in the investigation and monitoring work of broad-leaved Korean pine forests in this region, thereby achieving the goals of improving work efficiency and saving work costs.

Forest hydrology, the study of water dynamics within forested catchments, is crucial for understanding the intricate relationship between forest cover and water balances across different scales, from ecosystems to landscapes, or from catchment watersheds. The intensified global changes in climate, land use and cover, and pollution that occurred over the past century have brought about adverse impacts on forests and their services in water regulation, signifying the importance of forest hydrological research as a re-emerging topic of scientific interest. This article reviews the literature on recent advances in forest hydrological research, intending to identify leading countries, institutions, and researchers actively engaged in this field, as well as highlighting research hotspots for future exploration. Through a systematic analysis using VOSviewer, drawing from 17,006 articles retrieved from the Web of Science Core Collection spanning 2000–2022, we employed scientometric methods to assess research productivity, identify emerging topics, and analyze academic development. The findings reveal a consistent growth in forest hydrological research over the past two decades, with the United States, Charles T. Driscoll, and the Chinese Academy of Sciences emerging as the most productive country, author, and institution, respectively. The Journal of Hydrology emerges as the most co-cited journal. Analysis of keyword co-occurrence and co-cited references highlights key research areas, including climate change, management strategies, runoff-erosion dynamics, vegetation cover changes, paired catchment experiments, water quality, aquatic biodiversity, forest fire dynamics and hydrological modeling. Based on these findings, our study advocates for an integrated approach to future research, emphasizing the collection of data from diverse sources, utilization of varied methodologies, and collaboration across disciplines and institutions. This holistic strategy is essential for developing sustainable approaches to forested watershed planning and management. Ultimately, our study provides valuable insights for researchers, practitioners, and policymakers, guiding future research directions towards forest hydrological research and applications.

Small heat shock proteins (sHSPs) act as molecular chaperones that can prevent the accumulation of damaged proteins during abiotic stress, especially heat shock, but the mechanism is not clear. To study the function of sHSPs in Lenzites gibbosa, a common polypore in northern temperate forests that causes spongy white rot of broadleaf trees, under temperature stress, L. gibbosa mycelia were grown at 25 °C for 9 d, treated at 33 °C for 15, 30, 60, and 120 min before sequencing the transcriptomes. From among 32 heat shock protein (HSP) genes found in the screen of the transcriptome data, a highly expressed gene was cloned and named Lghsp17.4. RT-qPCR was used to analyze the expression of the gene Lghsp17.4 under heat shock and dye stress. Both treatments induced higher expression of Lghsp17.4 at the transcriptional level, indicating that Lghsp17.4 might function in the response to heat stress and dye degradation. We previously found that L. gibbosa generally had a heat shock reaction (HSR) during degradation of aromatic compounds, and HSPs were always produced with manganese peroxidases (MnPs) and other lignin-degrading enzymes. Therefore, we measured the activity of MnPs in L. gibbosa after 33 °C heat shock to analyze the relationship between MnPs expression and Lghsp17.4 expression. Heat shocks of 0–30 min increased MnPs activity, and the change in MnPs activity were closely positively correlated with the expression levels of Lghsp17.4 over time, indicating a potential connection and interaction between LgHSP17.4 and MnPs during the HSR in L. gibbosa. Thus, LgHSP17.4 might have a positive regulatory effect on the HSR in L. gibbosa and be a critical component of a stress resistance mechanism.

The survival strategy of plants is to adjust their functional traits to adapt to the environment. However, these traits and survival strategies of evergreen broad-leaved forest species are not well understood. This study examined 10 leaf functional traits (LFTs) of 70 common plant species in an evergreen broad-leaved forest in Huangshan Mountain to decipher their adaptive strategies. The phylogenetic signals of these LFTs were assessed and phylogenetically independent contrasts (PIC) and correlation analyses were carried out. LFTs were analyzed to determine their CSR (C: competitor, S: stress-tolerator, R: ruderal) strategies. The results show that plant species exhibit different leaf functional traits and ecological strategies (nine strategies were identified; the most abundant were S/CS and S/CSR strategies). Some traits showed significant phylogenetic signals, indicating the effect of phylogeny on LFTs to an extent. Trait variations among species suggest distinct adaptation strategies to environmental changes. The study species were mainly clustered on the C-S strategy axis, with a high S component. Species leaning toward the C-strategy end (e.g., deciduous species), favored a resource acquisition strategy characterized by higher specific leaf area (SLA), greater nutrient contents (N and P), lower leaf dry matter content (LDMC), and reduced nutrient utilization efficiency (C: N and C: P). Conversely, species closer to the S-strategy end (e.g., evergreen species) usually adopted a resource conservative strategy with trait combinations contrary to those of C-strategy species. Overall, this study corroborated the applicability of the CSR strategy at a local scale and provides insights into the varied trait combinations and ecological strategies employed by plant species to adapt to their environment. These findings contribute to a better understanding of the mechanisms involved in biodiversity maintenance.

Botryosphaeria laricina (larch shoot blight) was first identified in 1973 in Jilin Province, China. The disease spread rapidly and caused considerable damage because its pathogenesis was unknown at the time and there were no effective controls or quarantine methods. At present, it shows a spreading trend, but most research can only conduct physiological analyses within a relatively short period, combining individual influencing factors. Nevertheless, methods such as neural network models, ensemble learning algorithms, and Markov models are used in pest and disease prediction and forecasting. However, there may be fitting issues or inherent limitations associated with these methods. This study obtained B. laricina data at the county level from 2003 to 2021. The dataset was augmented using the SMOTE algorithm, and then algorithms such as XGBoost were used to select the significant features from a combined set of 12 features. A new stacking fusion model has been proposed to predict the status of B. laricina. The model is based on random forest, gradient boosted decision tree, CatBoost and logistic regression algorithms. The accuracy, recall, specificity, precision, F₁ value and AUC of the model reached 90.9%, 91.6%, 90.4%, 88.8%, 90.2% and 96.2%. The results provide evidence of the strong performance and stability of the model. B. laricina is mainly found in the northeast and this study indicates that it is spreading northwest. Reasonable means should be used promptly to prevent further damage and spread.

Temperate woodland vegetation is initially determined by spatiotemporal and historical factors, mediated by complex biotic interactions. However, catastrophic events such as disease outbreaks (e.g., sweet chestnut blight, ash dieback), infestations of insect pests, and human-accelerated climate change can create canopy gaps due to systematic decline in, or loss of, tree species that was once an important part of the canopy. Resultant cascade effects have the potential to alter the composition of woodland ecosystems quickly and radically, but inherent lag times make primary research into these effects challenging. Here, we explore change in woodland vegetation at 10 sites in response to canopy opening using the Elm Decline, a rapid loss of Ulmus in woodlands across northwestern Europe ~ 5800 years ago that coexisted alongside other stressors such as increasing human activity, as a palaeoecological analogue. For arboreal taxa, community evenness significantly decreased, within-site turnover significantly increased, and richness remained unchanged. Changes in arboreal taxa were highly site-specific but there was a substantial decline in woody climbing taxa, especially Hedera (ivy), across the majority of sites. For shrub taxa, richness significantly increased but evenness and turnover remained consistent. Interestingly, however, there was a significant increase in abundance of shrubs at 70% of sites, including Calluna (heather), Ilex (holly) and Corylus (hazel), suggesting structural change. Surprisingly, there was no change in richness, evenness or turnover for herb taxa, possibly because change was highly variable spatially. However, there was a marked uptick in the disturbance indicator Plantago (plantain). Overall, these findings suggest that woodlands with sustained reduction in, or loss of, a tree species that once formed an important part of the canopy has profound, but often spatially idiosyncratic, impacts on vegetation diversity (richness), composition (evenness), stability (turnover), and on abundance of specific taxa, especially within the shrub layer. Use of this palaeoecological analogue, which was itself complicated by cooccurring changes in human activity, provides a valuable empirical insight into possible cascade effects of similar change in canopy opening in contemporary settings, including Ash Dieback.

The defense mechanisms induced in wild Chinese pine (Pinus tabuliformis) in response to herbivores are not well characterized, especially in the field. To address this knowledge gap, we established a biological model system to evaluate proteome variations in pine needles after feeding by the Chinese pine caterpillar (Dendrolimus tabulaeformis), a major natural enemy and dominant herbivore. Quantitative tandem mass tag (TMT) proteomics and bioinformatics were utilized to systematically identify differentially abundant proteins implicated in the induced defense response of Chinese pine. We validated key protein changes using parallel reaction monitoring (PRM) technology. Pathway analysis revealed that the induced defenses involved phenylpropanoid, coumarin, and flavonoid biosynthesis, among other processes. To elucidate the regulatory patterns underlying pine resistance, we determined the activities of defense enzymes and levels of physiological and biochemical compounds. In addition, the expression of upstream genes for key proteins was validated by qRT-PCR. Our results provide new molecular insights into the induced defense mechanisms in Chinese pine against this caterpillar in the field. A better understanding of these defense strategies will inform efforts to breed more-resistant pine varieties.

The physiological structure and growth of trees in extreme environments (freezing temperatures, prolonged drought, wildfires, pest infestations, and diseases) can be inhibited, including radial growth, and stagnant growth or missing annual rings is highly possible. In this study, we analyzed the radial growth of Siberian larch (Larix sibirica) in the Hongshanzui area of the Altai Mountains, China. The overall missing ring rate at the sampling point was 2.39%, with years with the highest missing rings since meteorological site data were available (1960) identified as 1960, 1961, 1971, 1973, 1985, 1987, and 1995. Radial growth in high altitudes was mainly affected by temperatures in May and June (average temperature, average minimum temperature, and average maximum temperature). Frequent periods of freezing may lead to missing annual rings. However, while Larix sibirica shows resilience after prolonged freezing temperatures, it still requires time for the trees to return to normal growth levels.