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.

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.

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.

Larix resources in the Qinghai-Tibet Plateau have important ecological and economic values. However, the lack of genetic diversity background and related research hinders the development of conservation strategies. In this study, genetic diversity and distribution of five Larix species were investigated. Using 19 polymorphic microsatellite markers to study 272 representative individuals from 13 populations, the results show low genetic diversity at the population level, with variation explained mainly by differentiation among populations. The Larix populations were classified into two clades, one formed by eight populations, including three of the species in this study, L. kongboensis, L. speciosa, and L. potaninii var. australis. The other clade consists of five populations, including the other two species in this study, L. griffithii and L. himalaica. Genetic distance of the species was affected by geographical isolation and genetic diversity was mainly affected by altitude. The area suitable for Larix spp. decreased during the Last Glacial Maximum compared to the current distribution according to the niche model, but should increase in future climate scenarios (2050s), expanding westward along the Himalayas. These results provide an important scientific basis for the development of conservation strategies and further the sustainable utilization of Larix resources in the Qinghai-Tibet Plateau.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Gingko biloba accumulates high levels of secondary metabolites of pharmaceutical value. Ginkgo calli develop a typical browning that reduces its regenerative capacity and thus its usefulness. To elucidate the browning mechanism, histological, transcriptomic, and metabolic alterations were compared between green and browning calli derived from immature ginkgo embryos. Histological observations revealed that browning calli had a more loosely arranged cell structure and accumulated more tannins than in green calli. Integrated metabolic and transcriptomic analyses showed that phenylpropanoid metabolism was specifically activated in the browning calli, and 428 differentially expressed genes and 63 differentially abundant metabolites, including 12 flavonoid compounds, were identified in the browning calli compared to the green calli. Moreover, the expression of flavonol synthase (FLS) and UDP-glucuronosyl-transferase (UGT) genes involved in the flavonoid pathway was more than tenfold higher in browning calli than in green calli, thus promoting biosynthesis of flavonol, which serves as a substrate to form glycosylated flavonoids. Flavonoid glycosides constituted the major coloring component of the browning calli and may act in response to multiple stress conditions to delay cell death caused by browning. Our results revealed the cellular and biochemical changes in browning callus cells that accompanied changes in expression of browning-related genes, providing a scientific basis for improving ginkgo tissue culturability.

The stability of monocultural, even-aged spruce forests at lower altitudes in Central Europe is seriously threatened by the prospects of global climate change. The thermostability and water use efficiency of their photosynthetic apparatus might play a vital role in their successful acclimation. In this study, photosystem II (PSII) performance (OJIP transient, rapid light curves) and thermostability were analyzed in Norway spruce (Picea abies (L.) Karst.) throughout the growing season of the exceptionally warm year 2018 (May–September) in the Western Carpathians, Slovakia. These measurements were accompanied by analysis of pigment concentrations in the needles. In addition, gas-exchange temperature curves were produced weekly from June until September to obtain intrinsic water use efficiencies. At the beginning of the growing season, needles exposed to heat stress showed significantly higher basal fluorescence and lower quantum yield, performance index, critical temperature thresholds of PSII inactivation and non-photochemical yield in comparison to other months. The overall thermostability (heat-resistance) of PSII peaked in July and August, reflected in the lowest basal fluorescence and the highest quantum yield of PSII, critical temperature thresholds and yield of non-photochemical quenching under heat stress. Additionally, the ratio between chlorophyll and carotenoids was the highest in August and had a positive impact on PSII thermostability. Moreover, the high-temperature intrinsic water use efficiency was significantly higher during July and August than in June. Results show that 15-year-old trees of Picea abies at 840 m a.s.l. exhibited acclimative seasonal responses of PSII thermostability and intrinsic water use efficiency during an exceptionally warm year. Our results suggest that mountainous P. abies at lower altitudes can acclimate their photosynthetic apparatus to higher temperatures during summer.

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.

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.

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.

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.

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.

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.

Periodical cicadas (Magicicada spp.) are endemic to deciduous forests in the eastern United States. In successional forests, they must partition resources such as host trees to coexist. We measured tree size, emergence holes, oviposition scar bundles, and chorusing center abundances of Magicicada species on 12 common tree species in a deciduous forest to understand host-tree use. We predicted that the abundance of periodical cicadas and use of specific host-tree species would change depending on the Magicicada species and tree life stage. We considered the size of the tree (diameter at breast height) as a covariate to control for tree size and collected eggs for a greenhouse experiment to assess whether nymphs prefer to feed on Quercus rubra or Acer saccharum. More emergence holes were found below Quercus species than any other tree species. The abundance of periodical cicadas on host trees used for chorusing centers varied depending on the Magicicada species, but were most abundant on Quercus species. Oviposition scar bundles were also more frequent on Quercus. More nymphs were found on Quercus than Acer in the nymph preference study. Though periodical cicadas used Quercus hosts more than other tree species, their abundances on different host tree sizes and species differed significantly. Periodical cicada species may use specific host species and life stages as a way to partition resources and minimize competition among the Magicicada species during emergence years.

Ecological stoichiometry is an important indicator of biogeochemical cycles and nutrient limitations in terrestrial ecosystems. However, little is known about the response of ecological stoichiometry to plant growth. In this study, carbon (C), nitrogen (N), and phosphorus (P) concentrations were evaluated in plant tissues (trees, shrubs, and herbs), litter, and soil of young (≤ 40-year-old), middle-aged (41–60-year-old), near-mature (61–80-year-old), and mature (81–120-year-old) Quercus secondary forests on the Loess Plateau, China. Vegetation composition, plant biomass, and C stock were determined to illustrate their interaction with stoichiometry. Only tree biomass C significantly increased with stand development. Leaf N and trunk P concentrations generally increased, but branch P decreased with growth stage. Fine roots had the highest C and P concentrations at the middle-aged stage. In contrast, shrubs, herbs, litter, and soil C:N:P stoichiometry did not change significantly during stand development. Leaf N and P were positively correlated with soil C, N, P, and their ratios. However, there was no significant correlation between litter and leaves in terms of C:N:P stoichiometry. A redundancy analysis showed that soil N best explained leaf N and P variance, and tree biomass and C stock were related to biotic factors such as tree age and shrub biomass. Hierarchical partitioning analysis indicated that, compared with soil or litter variables, stand age only accounted for a relatively small proportion of leaf C, N, and P variation. Thus, secondary Quercus ecosystems might have inherent ability to maintain sensitive responses of metabolically active organs to environmental factors during stand aging. The results of this work help to elucidate the biogeochemical cycling of secondary forest ecosystems in tree development, provide novel insights into the adaptation strategies of plants in different organs and growth stages, and could be used to guide fertilization programs and optimize forest structure.

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.

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.

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.

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.

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.

With the expansion of eucalyptus crops to areas with severe water limitations, physiological studies involving eucalyptus clones to identify those that are tolerant to water stress become important. The objective of this study was to assess morphological and physiological responses by eucalyptus clones subjected to drought stress and rehydration. The experiment consisted of three eucalyptus clones: VC865, I224 and I144 and two water regimes: control and water stress followed by rehydration, with six replicates. Leaf water potential, gas exchange, maximum quantum efficiency of photosystem II and plant height and stem diameter were evaluated under drought stress and rehydration. After 6 d of rehydration, the number of leaves, leaf area and dry mass of root, leaf, stem and their total were evaluated. All clones showed intense reduction of gas exchange during the drought stress period, and only VC865 and I144 showed rapid recovery with 3 d of rehydration. Clone I224 showed greater reduction in height, stem diameter, number of leaves, water potential at midday (Ψ _{w Midday}), and maximum quantum efficiency of photosystem II (F _v/F _m). Clones VC865 and I144 showed lower reductions in Ψ _{w Midday} and F _v/F _m under stress. VC865 had lower reductions in leaf number, leaf area and higher leaf dry mass, while clone I144 had higher height and lower reduction in root dry mass under. Both these clones showed higher water use efficiency with 3 d of rehydration. These different phenotypic plasticities gave the clones VC865 and I144 efficient mechanisms of acclimatization to stress and more drought tolerance, enhancing their greater capacity for recovery after stress, which allowed lower dry mass reduction. Clone I224, however, was more susceptible to drought stress, undergoing greater physiological damage with only partial recovery during rehydration.

Lectins are natural proteins in animals, plants, and microorganisms and can be divided into 12 families. These lectins play important roles in various environmental stresses. Some polyploid plants show tolerance to environmental stresses and to insect pests. However, the mechanism of stress tolerance is unclear. Tetraploid Robinia pseudoacacia (4×) under salt stress showed higher tolerance than diploid R. pseudoacacia (2×). As lectin can improve stress tolerance, it was questioned whether the stress resistance of polyploid plants was related to the lectin protein. In this study, salt resistance of lectin gene TRpL1 was verified by its over-expression in plants. In addition, salt resistance of lectin protein by E. coli strains was detected. The data revealed that the over-expression transgenic plants of TRpL1 showed better salt tolerance than control plants under salt stress, and the TRpL1-expressing strain also grew better in the medium with added NaCl. Therefore, tetraploid plants can resist salt stress through TRpL1 protein regulation.

The diameter distribution of trees in a stand provides the basis for determining the stand’s ecological and economic value, its structure and stability and appropriate management practices. Scots pine (Pinus sylvestris L.) is one of the most common and important conifers in Turkey, so a well-planned management schedule is critical. Diameter distribution models to accurately describe the stand structure help improve management strategies, but developing reliable models requires a deep understanding of the growth, output and constraints of the forests. The most important information derived by diameter distribution models is primary data on horizontal stand structure for each diameter class of trees: basal area and volume per unit area. These predictions are required to estimate the range of products and predicted volume and yield from a forest stand. Here, to construct an accurate, reliable diameter distribution model for natural Scots pine stands in the Türkmen Mountain region, we used Johnson’s S _B distribution to represent the empirical diameter distributions of the stands using ground-based measurements from 55 sample plots that included 1219 trees in natural distribution zones of the forests. As an alternative, nonparametric approach, which does not require any predefined function, an artificial intelligence model was constructed based on support vector machine methodology. An error index was calculated to evaluate the results. Overall, both Johnson’s S _B probability density function with a three-parameter recovery approach and the support vector regression methodology provided reliable estimates of the diameter distribution of these stands.

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.

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.

Air temperature and photoperiod play an important role in the seedling development for tropical forest species. Both variables are sensitive to climate, and so evaluating thermal and photoperiodic effects on seedling development is fundamental, especially for climate change studies. Methods to quantify thermal time and the energy required for plants to reach a development stage include air temperature and cardinal temperatures. The photoperiod will also affect physiological reactions of a plant and thus its development. Here we evaluated the six thermal time methods widely used to compute thermal requirement, and identified the influence of the photoperiod from the 2015 and 2016 growing seasons and 12 sowing dates in Itajubá, Minas Gerais state, Brazil, on seedling development of three native tropical forest species Psidium guajava L. (Myrtaceae), Citharexylum myrianthum Cham. (Verbenaceae), and Bixa orellana L. (Bixaceae). The method used to quantify thermal time influenced the analytical results of seedling development; the one that considered three cardinal temperatures and compared them with the mean air temperature (Method 5) performed better in computing thermal requirements. The influence of photoperiod on seedling development was inconclusive for the three species, but all three developed better in mild temperatures (between 13.3 °C and 26.9 °C) with a photoperiod shorter than 13 h.