Eucalyptus harvest residues are attractive energy production resources for the forestry industry. However, their removal can have adverse impacts on soil quality and forest productivity, especially in sandy soils. In this study, we assessed the effects of Eucalyptus harvest residue managements with variable intensity on forest productivity and on physical, chemical, and biological indicators of the soil quality. The experiment was conducted in a Quartzipsamment (33 g kg⁻¹ clay) planted with Eucalyptus saligna in Barra do Ribeiro in southern Brazil. Before the Eucalyptus was planted, residues from the previous rotation were subjected to five different management treatments: (1) FRM, in which all forest residues (bark, branches, leaves, and litter) were allowed to remain on the soil and only trunk wood was removed; (2) FRMB, in which was identical to FRM except that bark was also removed; (3) FRMBr, in which only trunk wood and branches were removed; (4) FRR, which involved removing all types of residues (bark, branches, leaves, and litter); and, (5) FRRs, in which all forest residues from the previous rotation were removed, and leaves and branches from the new plantation were prevented from falling onto the soil surface using a shade net. Six years after planting, soil samples were collected at four different depths (0–2.5, 2.5–5, 5–10, and 10–20 cm) to determine 17 soil chemical, physical, and biological indicators. The results were combined into a soil quality index (SQI) using the principal component analysis approach. The SQI reduced by 30%, in the 0–20 cm layer, due to removal of harvest residues from the previous rotation, and collection of litter before it falls on the ground. The main drivers of SQI reduction were the principal components associated with soil organic matter and biological activity. Furthermore, the SQI was positively linearly related to tree height at P < 0.01 and to tree diameter at breast height at P = 0.07. The adverse impact on soil quality and forest productivity in our study indicates that removal of Eucalyptus harvest residues from sandy soils should be avoided.

Managing mature Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] stands to emulate the structural complexity of natural old-growth forest requires identifying structural targets at the sub-stand level at which neighborhood dynamics and patchy disturbance shape structure. We therefore sought to describe the archetypal shapes of predominant sub-stand diameter distribution types (DDTs) observed in natural tree neighborhoods in stands comprising a chronosequence (ca. 120–450+ yrs) encompassing mature, vertical diversification, and horizontal diversification development stages. The ten 1.0 ha stands are located in the southcentral Oregon Cascades, USA. Building on the known spatial position of each tree, natural tree neighborhoods were identified using the floating neighborhood approach based on spatial tessellation connecting neighboring trees at the first- (mean 61 m²) through fifth- (mean 2058 m²) order scales. Cluster analysis was then used to objectively identify the most predominant DDTs among the relative tree size distributions observed in the trans-scale neighborhoods within each stand. Repeated measures regression was used to classify each DDT to one of six observed archetypal shapes: negative exponential, unimodal, rotated sigmoid, bimodal, concave, or multi-modal. Only three of the 81 observed DDTs deviated by < 10% from the stand average, while every stand had at least one DDT that deviated by > 50% (maximum 83%). Within each stand, five to ten predominant DDTs were observed, which deviated from the stand average by 30–48% and were characterized by two to five different archetypal shapes. Consequently, in some stands the majority of tree neighborhoods were best characterized by a different shape from that assigned at the stand level. Deviation from the stand average increased from the youngest stand in the mature development stage through the middle stands in the vertical diversification stage to the oldest stands in the horizontal diversification stage. The complexity of DDT shapes tended to increase along the chronosequence (from negative exponential and uniform toward concave and multi-modal), with shape richness highest mid-sequence and evenness peaking in the oldest stands. The high diversity of sub-stand structural complexity reduces the utility of stand-level diameter distributions as old-growth restoration targets. However, the presence in early-sequence stands of sub-stand diameter distributions common to later-sequence stands may facilitate active management at the neighborhood level to promote future old-growth condition. Restoration of sub-stand diameter structures would likely require combining spatial perspectives, such as by augmenting tree-level crop-tree management with diameter distribution targets for the resulting tree neighborhoods.

To evaluate the relationships among clones and open pollinated families from the same plus trees and to select elite breeding materials, growth, and wood characteristics of 33-year-old Pinus koraiensis clones and families were measured and analyzed. The results show that growth and wood characters varied significantly. The variation due to clonal effects was higher than that of family effects. The ratio of genetic to phenotypic coefficient of variation of clones in growth and wood traits was above 90%, and the repeatability of these characteristics was more than 0.8, whereas the ratio of genetic to phenotypic coefficient of variation of families was above 90%. The broad-sense heritability of all characteristics exceeded 0.4, and the narrow-sense family heritability of growth traits was less than 0.3. Growth characteristics were positively correlated with each other, but most wood properties were weakly correlated in both clones and families. Fiber length and width were positively correlated between clones and families. Using the membership function method, eleven clones and four families were selected as superior material for improved diameter growth and wood production, and two families from clonal and open-pollinated trees showed consistently better performance. Generally, selection of the best clones is an effective alternative to deployment of families as the repeatability estimates from clonal trees were higher than narrow-sense heritability estimates from open pollinated families. The results provide valuable insight for improving P. koraiensis breeding programs and subsequent genetic improvement.

Fine roots (< 2 mm) play vital roles in water and nutrient uptake. However, intraspecific variations in their chemical traits and their controlling mechanisms remain poorly understood at a regional scale. This study examined these intraspecific variations in fine roots in Masson pine (Pinus massoniana Lamb.) plantations across subtropical China and their responses to environmental factors. Root nitrogen (N) and phosphorus (P) concentrations and their mass ratios (N:P) ranged from 3.5 to 11.7 g kg⁻¹, 0.2 to 0.9 g kg⁻¹, and 7.8 to 51.6 g kg⁻¹, respectively. These three chemical traits were significantly different between sites and in longitudinal patterns across subtropical China. Mean annual temperature was positively related to root N concentration but negatively related to root P concentration. There were significant, negative relationships between clay content and root P concentration and between pH and root N concentration. Available N had no significant relationship with root N concentration, while available P was a significantly positive relationship with root P concentration. The combined effects of altitude, climate (temperature and precipitation) and soil properties (pH, clay content, available N and P) explained 26% and 36% of the root N and P concentrations variations, respectively. These environmental variables had direct and indirect effects and exhibited disproportionate levels of total effects on root N and P concentrations. Root N and P concentrations explained 35% and 65% variations in their mass ratios, respectively. The results highlight different spatial patterns of chemical traits and various environmental controls on root N and P concentrations in these ecosystems. More cause-effect relationships of root chemical traits with abiotic and biotic factors are needed to understand nutrient uptake strategies and the mechanisms controlling intraspecific variations in plant traits.

Accurate decay detection and health assessment of trees at low temperatures is an important issue for forest management and ecology in cold areas. Low temperature ice formation on tree health assessment is unknown. Because electric resistance tomography and stress wave tomography are two widely used methods for the detection of tree decay, this study investigated the effect of ice content on trunk electrical resistance and stress wave velocity to improve tree health assessment accuracy. Moisture content, trunk electrical resistance and stress wave velocity using time domain reflectometry were carried out on Larix gmelinii and Populus simonii. Ice content is based on moisture content data. The ice content of both species showed a trend of increasing and then decreasing. This was opposite with ambient temperatures. With the decrease of temperatures, daily average ice content increased, but the range narrowed gradually and both electrical resistance and stress wave velocity increased. Both increased rapidly near 0 °C, mainly caused by ice formation (phase change and freezing of free water) in live trees. In addition, both are positively correlated with ice content. The results suggest that ice content should be considered for improving the accuracy of tree decay detection and health evaluation using electric resistance tomography and stress wave velocity methods under low temperatures.

Plant tolerance to aluminum (Al) toxicity can be enhanced by an ectomycorrhizal (ECM) fungus through biological filtering or physical blockage. To understand the roles of ECM colonization in Al absorption with regard to Al tolerance, Pinus massoniana seedlings were inoculated with either Lactarius deliciosus (L.:Fr.) Gray isolate 2 or Pisolithus tinctorius (Pers.) Coker et Couch isolate 715 and cultivated in an acid yellow soil with or without 1.0 mM Al³⁺ irrigation for 10 weeks. Biomass production, Al bioaccumulation and transport in seedlings colonized by the two ECM fungi were compared, and the three absorption kinetics (pseudo-first order, pseudo-second order and intraparticle diffusion) models used to evaluate variances in root Al³⁺ absorption capacity. Results show that both fungi increased aboveground biomass and Al tolerance of P. massoniana seedlings, but L. deliciosus 2 was more effective than P. tinctorius 715. Lower Al absorption capacity, fewer available active sites and decreased affinity and boundary layer thickness for Al³⁺, and higher Al accumulation and translocation contributed to the increased Al tolerance in the ECM-inoculated seedlings. These results advance our understanding of the mechanisms and strategies in plant Al-tolerance conferred by ECM fungi and show that inoculation with L. deliciosus will better enhance Al tolerance in P. massoniana seedlings used for forest plantation and ecosystem restoration in acidic soils, particularly in Southwest China and similar soils worldwide.

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.

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.

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.

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.

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.

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.

A solid understanding of the efficiency of early selection for fiber dimensions is a prerequisite for breeding slash pine (Pinus elliottii Engelm.) with improved properties for pulp and paper products. Genetic correlations between size of fibers, wood quality and growth properties are also important. To accomplish effective early selection for size of fibers and evaluate the impact for wood quality traits and ring widths, core samples were collected from 360 trees of 20 open-pollinated Pinus elliottii families from three genetic trials. Cores were measured by SilviScan, and the age trends for phenotypic values, heritability, early-late genetic correlations, and early selection efficiency for fiber dimensions, such as tangential and radial fiber widths, fiber wall thickness and fiber coarseness, and their correlations with microfibril angle (MFA), modulus of elasticity (MOE), wood density and ring width were investigated. Different phenotypic trends were found for tangential and radial fiber widths while fiber coarseness and wall thickness curves were similar. Age trends of heritability based on area-weighted fiber dimensions were different. Low to moderate heritability from pith to bark (~ 0.5) was found for all fiber dimension across the three sites except for tangential fiber width and wall thickness at the Ganzhou site. Early-late genetic correlations were 0.9 after age of 9 years, and early selection for fiber dimensions could be effective due to strong genetic correlations. Our results showed moderate to strong positive genetic correlations for modulus of elasticity and density with fiber dimensions. The effects on fiber dimensions were weak or moderate when ring width or wood quality traits were selected alone. Estimates of efficiency for early selection indicated that the optimal age for radial fiber width and fiber coarseness was 6–7 years, while for tangential fiber width and wall thickness was 9–10 years.

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.

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.

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.

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.

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.

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.

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.

Fraxinus mandshurica Rupr. is one of the main afforestation species in northeast China, and there is great demand for improved F. mandshurica varieties. The results of an investigation into and analysis of the growth traits of F. mandshurica provenances and families showed that there were significant differences in different periods. However, variations in growth traits decreased year by year. There was a significant negative correlation between tree heights of the provenances and sunshine hours in their areas of origin. The provenances of Xinglong, Hailin and Wuchang were selected based on the volume of 18-year-old trees. The average genetic gain from the selection of fast-growing provenances was 19.4%. Ten superior fast-growing families were selected. The average volume of the selected families was 22.6%, higher than that of all families. The correlation coefficient between heights at 6-year-old and at 18a was 0.838 for provenances, and between heights at 4-year-old and at 18-year-old was 0.303 for families. These results indicate that early selection for height in provenances or families could be performed at 6 years or 4 years, respectively. Early selection for DBH and volume in families could start at 8 years.

Due to considerable deforestation in North Korea, there is a need to plan forest restoration programs based on scientific forest management. In this study, a methodology was developed for estimating the site index values of six major tree species and the forest productivity potential. The site index values of these tree species were derived in South Korea using the Chapman-Richards equation. These values were used with data from the 6th National Forest Inventory, which included 20 types of edaphic, topographic, and climatic factors, and random forest analysis—a widely used machine learning technique for spatial prediction—to develop a new model for estimating the site index values of these species across South Korea. The prediction accuracy of this model was evaluated using the root mean square error. The results show that the prediction accuracy was high, with a root mean square error of ~ 1 m. Moreover, the importance of the variables related to climate and geography was generally high. The proposed site index estimation model for six tree species was applied across North Korea, and its effectiveness tested by comparing the estimated values with those reported in literature from North Korea. The differences between the model outputs and recorded data in the northern alpine regions were presumably due to the lack of data for high-altitude regions in South Korea. This model is based on the determination of the suitability of tree species in restoration efforts. Therefore, it can contribute to the evaluation of forest productivity in North Korea and may help plan efficient forest restoration programs.

Though riparian areas generally have a shallow water table and higher soil moisture compared to upslope areas, climatic seasonality may trigger water repellency in tropical riparian forests, which, if persistent, could negatively affect essential ecosystem functions related to water resources protection such as reduced overland-flow, sediment transport, and nutrient filtration. The objective of this study was to answer the following: can tropical riparian forests develop water repellency? If so, does water repellency affect infiltration on a seasonal basis? For this, water repellency and infiltration were measured in a grid of 72 points during a dry and a wet month of a tropical riparian forest with a shallow water table in a region with highly marked climatic seasonality. Water repellency and infiltration were significantly different between the wet and dry months. Water repellency affected negatively infiltration in the dry month, its effect in the wet month was insignificant. As a result, a higher infiltration capacity was observed over the wet period. Previous research has claimed that the development and persistence of repellency in soils could promote other hydrological processes such as overland flow. The findings shown here demonstrate that such phenomenon does not persist longer than the dry season.

Doubled haploid (DH) plants have been widely used for breeding and biological research in crops. Populus spp. have been used as model woody plant species for biological research. However, the induction of DH poplar plants is onerous, and limited biological or breeding work has been carried out on DH individuals or populations. In this study, we provide an effective protocol for poplar haploid induction based on an anther culture method. A total of 96 whole DH plant lines were obtained using an F₁ hybrid of Populus simonii ×  P. nigra as a donor tree. The phenotypes of the DH population showed exceptionally high variance when compared to those of half-sib progeny of the donor tree. Each DH line displayed distinct features compared to those of the other DH lines or the donor tree. Additionally, some excellent homozygous lines have the potential to be model plants in genetic and breeding studies.

Plantations of Rupprecht’s larch (Larix principis-rupprechtii) have been widely established in the drylands of northwest and north China under traditional fast-growing plantation management strategies. These strategies and the long-term logging ban have led to over-populated stands with lower structural and functional stability, less economic benefit and higher water consumption. To guide the sustainable management of larch plantations, field surveys and historical data compilation were undertaken in the Liupan Mountains of northwest China. The main influencing factors (stand structure and site condition) and their effects on mean tree height, mean DBH and timber volumes were determined based on up-boundary line analysis. Tree growth models coupling the effects of tree age, stand density, and elevation were established. Both height and DBH markedly increased initially and then slowly with tree age, decreased with stand density, and showed unimodal change with elevation. The coupled growth models accounted for 72–78% of the variations in tree height, DBH and timber growth. Recommendations for future plantation management are: (1) prolong the rotation to at least 60 years to produce large-diameter, high-quality timber and maintain greater carbon stocks; (2) zone the target functions of stands by elevation; and, (3) reduce stand density for balanced supply of multiple ecosystem services. The growth models developed can predict growth response of larch plantations to density alteration under given ages and elevations, and assist the transformation from traditional management for maximum timber production to site-specific and multifunctional management with longer rotations and moderate tree density.

Inventory data were available from 96 plots of even-aged, monoculture, tall-open forests of Eucalyptus pilularis Smith, aged 2–63 years, growing in sub-tropical regions along the east coast of Australia. A model was developed relating the maximum possible stem basal area growth rate of individual trees to their stem basal area. For any tree size, this maximum increased as site productivity increased. However, the size at which this maximum occurred decreased as productivity increased. Much research has shown that, at any stand age, trees of a particular stem basal area are taller on more productive sites than on less productive ones. Taller trees incur greater respiratory costs to ensure maintenance of the photosynthetic capacity of their canopies; this reduces their growth rates. It was concluded that trees with larger basal areas will have the maximum possible growth rate on a less productive site, whilst trees with smaller basal areas will have the maximum possible on a more productive site. The model developed may constitute the first stage of a complete individual tree growth model system to predict wood yields from these forests.

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.

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.

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.

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.

Red osier dogwood (Cornus sericea L.), widely distributed throughout North America, is essential for wildlife, thus biodiversity. It is recommended for reclamation or revegetation of sites disturbed by oil and gas extraction because it tolerates a wide range of soil types and high pH levels. Since germination of this species is extremely difficult with long stratification requirements and poor germination, cuttings facilitate propagation. In this study, to develop techniques to propagate the species from stem cuttings, four concentrations of indole-3-butyric acid (IBA) and two cutting ages previous year’s growth (PYG) and current year’s growth (CYG) were investigated for survival and growth. After 4 months, survival rate, height growth, and shoot biomass from PYG cuttings were enhanced with IBA. In contrast, IBA did not affect these parameters in CYG cuttings. Root morphology was significantly affected by IBA concentration and cutting age. IBA, at higher concentrations, increased root surface and length. Total root surface area and length of PYG cuttings were increased, which may facilitate the absorption of essential resources and consequently increase growth. The results indicate that increasing the concentration of IBA may be an effective way to have better plant survival and growth of previous year’s cuttings in red osier dogwood.

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.

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.

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.

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.

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.