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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The number and composition of species in a community can be quantified with α-diversity indices, including species richness (R), Simpson’s index (D), and the Shannon–Wiener index ($H^\prime$). In forest communities, there are large variations in tree size among species and individuals of the same species, which result in differences in ecological processes and ecosystem functions. However, tree size inequality (TSI) has been largely neglected in studies using the available diversity indices. The TSI in the diameter at breast height (DBH) data for each of 999 20 m × 20 m forest census quadrats was quantified using the Gini index (GI), a measure of the inequality of size distribution. The generalized performance equation was used to describe the rotated and right-shifted Lorenz curve of the cumulative proportion of DBH and the cumulative proportion of number of trees per quadrat. We also examined the relationships of α-diversity indices with the GI using correlation tests. The generalized performance equation effectively described the rotated and right-shifted Lorenz curve of DBH distributions, with most root-mean-square errors (990 out of 999 quadrats) being < 0.0030. There were significant positive correlations between each of three α-diversity indices (i.e., R, D, and $H^\prime$) and the GI. Nevertheless, the total abundance of trees in each quadrat did not significantly influence the GI. This means that the TSI increased with increasing species diversity. Thus, two new indices are proposed that can balance α-diversity against the extent of TSI in the community: (1 − GI) ×  D, and (1 − GI) × $H^\prime$. These new indices were significantly correlated with the original D and $H^\prime$, and did not increase the extent of variation within each group of indices. This study presents a useful tool for quantifying both species diversity and the variation in tree sizes in forest communities, especially in the face of cumulative species loss under global climate change.

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

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

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

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

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

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

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

Betula platyphylla and Betula costata are important species in mixed broadleaved-Korean pine (Pinus koraiensis) forests. However, the specific ways in which their growth is affected by warm temperatures and drought remain unclear. To address this issue, 60 and 62 tree-ring cores of B. platyphylla and B. costata were collected in Yichun, China. Using dendrochronological methods, the response and adaptation of these species to climate change were examined. A “hysteresis effect” was found in the rings of both species, linked to May–September moisture conditions of the previous year. Radial growth of B. costata was positively correlated with the standardized precipitation-evapotranspiration index (SPEI), the precipitation from September to October of the previous year, and the relative humidity in October of the previous year. Growth of B. costata is primarily restricted by moisture conditions from September to October. In contrast, B. platyphylla growth is mainly limited by minimum temperatures in May–June of both the previous and current years. After droughts, B. platyphylla had a faster recovery rate compared to B. costata. In the context of rising temperatures since 1980, the correlation between B. platyphylla growth and monthly SPEI became positive and strengthened over time, while the growth of B. costata showed no conspicuous change. Our findings suggest that the growth of B. platyphylla is already affected by warming temperatures, whereas B. costata may become limited if warming continues or intensifies. Climate change could disrupt the succession of these species, possibly accelerating the succession of pioneer species. The results of this research  are of great significance for understanding how the growth changes of birch species under warming and drying conditions, and contribute to understanding the structural adaptation of mixed broadleaved-Korean pine (Pinus koraiensis) forests under climate change.

Understanding the relationship between forest management and water use efficiency (WUE) is important for evaluating forest adaptability to climate change. However, the effects of thinning and understory removal on WUE and its key controlling processes are not well understood, which limits our comprehension of the physiological mechanisms of various management practices. In this study, four forest management measures (no thinning: NT; understory removal: UR; light thinning: LT; and heavy thinning: HT) were carried out in Pinus massoniana plantations in a subtropical region of China. Photosynthetic capacity and needle stable carbon isotope composition (δ ¹³C) were measured to assess instantaneous water use efficiency (WUE_inst) and long-term water use efficiency (WUE_i). Multiple regression models and structural equation modelling (SEM) identified the effects of soil properties and physiological performances on WUE_inst and WUE_i. The results show that WUE_inst values among the four treatments were insignificant. However, compared with the NT stand (35.8 μmol·mol⁻¹), WUE_i values significantly increased to 41.7 μmol·mol⁻¹ in the UR, 50.1 μmol·mol⁻¹ in the LT and 46.6 μmol·mol⁻¹ in HT treatments, largely explained by photosynthetic capacity and soil water content. Understory removal did not change physiological performance (needle water potential and photosynthetic capacity). Thinning increased the net photosynthetic rate (A _n) but not stomatal conductance (g _s) or predawn needle water potential (ψ _pd), implying that the improvement in water use efficiency for thinned stands was largely driven by radiation interception than by soil water availability. In general, thinning may be an appropriate management measure to promote P. massoniana WUE to cope with seasonal droughts under future extreme climates.

Soil pedestals have long been used as qualitative indicators of soil splash erosion. In rangelands, plant-capped pedestals, generally grass tussocks, have also been used to quantitatively estimate soil loss since the first half of the twentieth century. In agricultural lands, forests, and badlands, stone-capped pedestals have been used as qualitative and semi-quantitative indicators of active, ‘extreme’ erosion. Little work has been reported on using capstone pedestal data for quantifying soil loss. We postulate that three distinct capstone pedestal types may be present in any given location and that a detailed analysis of a pedestal height histogram may be used to recognize their populations. This analysis can subsequently inform if soil loss can be reliably estimated and if so, which of the existing methods using pedestal height data will provide more accurate results. The three proposed capstone pedestal types are: (1) neo-pedestals formed underneath surface stones exposed by (partial) removal of the soil surface cover; (2) endo-pedestals formed underneath stones that were buried in the soil but have been exposed by erosion; and (3) phoenix-pedestals formed underneath stones from collapsed pedestals. In the pedestal height histogram of any given location, a skew to smaller heights may indicate the existence of endo- and/or phoenix-pedestals, which may be revealed as a bi-(or tri) modal distribution when using a smaller bin size. This concept was applied to a case study where soil loss had been monitored for control plots and mulched plots during a 5-year period following wildfire in a eucalypt plantation. We measured pedestal heights and used methods to quantitatively assess soil loss from soil pedestal data in the available literature. Soil pedestal data at the end of the 5-year period under or overestimated soil loss in the control treatment, with results ranging from 60 to 115% of measured soil loss, depending on the method. It is postulated that phoenix- and endo-pedestals may be a driving factor behind the observed discrepancies. We discuss how future research may provide more insight into dominant processes, and how frequency distributions may be used to select the best methods for estimating soil loss from pedestals.

In our previous screening of the transcriptome of the causal agent of the devastating pine wilt disease, pine wood nematode (PWN, Bursaphelenchus xylophilus), after treatment with the nematicide fomepizole, Surfeit locus gene sft-4, which encodes a regulatory factor, was found to be downregulated. In situ hybridization results showed that the sft-4 was continuously expressed from egg to adult and was especially high in the reproductive system. Here in a study of the effect of RNA interference (RNAi) of sft-4 and recombinant SFT-4 on PWN activity, treatment with sft-4 dsRNA inhibited feeding, reproduction, oviposition and egg hatching of PWN with the greatest inhibition on reproduction and oviposition, whereas recombinant SFT-4 had the opposite effect. In addition, RNAi of sft-4 changed the female–male ratio and lifespan of PWN. In bioassays of PWNs, with RNAi of sft-4 on seedlings and 2-year-old Pinus thunbergii trees, none of the treated plants developed symptoms during the monitoring period, indicating that virulence of PWNs was either significantly weakened. These results indicate that the influence of sft-4 on PWN pathogenicity may be mainly through regulating reproductive function of PWN and its lifespan.

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

Recent methodological advances in quantitative wood anatomy have provided new insights into the climatic responses of radial growth at the scale of cell structure of tree rings. This study considered long-term chronologies of tracheid measurements, indexed by a novel approach to separate their specific climatic responses from signal recorded in cell production (closely reflected in tree-ring width). To fill gaps in understanding the impact of climate on conifer xylem structure, Scots pine (Pinus sylvestris L.) trees > 200 years old were selected within the forest-steppe zone in southern Siberia. Such habitats undergo mild moisture deficits and the resulting climatic regulation of growth processes. Mean and maximum values of cell radial diameter and cell wall thickness were recorded for each tree ring. Despite a low level of climatogenic stress, components of cell chronologies independent of cambial activity were separated to obtain significant climatic signals revealing the timing of the specific stages of tracheid differentiation. Cell expansion lasted from mid-April to July and was impacted similarly to tree-ring width (stimulated by precipitation and stressed by heat), maximum cell size formed late June. A switch in the climatic responses of mean anatomical traits indicated transition to latewood in mid-July. Secondary wall deposition lasted until mid-September, suppressed by end of season temperatures. Generally, anatomical climatic responses were modulated by a less dry May and September compared with summer months.

The regeneration of Tetracentron sinense Oliv. is poor in the understory and in open areas due to the characteristics of natural regeneration of the species on forest edges and in gaps. It is unclear whether different light intensities in various habitats affect eco-physiological characteristics of saplings and their natural regeneration. In this study, the light intensity in T. sinense habitats was simulated by artificial shading (L1: 100% NS (natural sunlight) in the open; L2: 50% NS in a forest gap or edge; L3: 10% NS in understory) to investigate differences in morphology, leaf structure, physiology, and photosynthesis of 2-year-old saplings, and to analyze the mechanism of light intensity on sapling establishment. Significant differences were observed in morphology (including leaf area, and specific leaf area) under different light intensities. Compared to L1 and L3, chloroplast structure in L2 was intact. With increasing time, superoxide dismutase (SOD) and catalase (CAT) activities in L2 became gradually higher than under the other light intensities, while malondialdehyde (MDA) content was opposite. Shading decreased osmoregulation substance contents of leaves but increased chlorophyll. The results suggest that light intensities significantly affect the eco-physiological characteristics of T. sinense saplings and they would respond most favorably at intermediate levels of light by optimizing eco-physiological characteristics. Therefore, 50% natural sunlight should be created to promote saplings establishment and population recovery of T. sinense during in situ conservation, including sowing mature seeds in forest edges or gaps and providing appropriate shade protection for seedlings and saplings in the open.

Changes in annual radial growth is an important indication of climate change. Dendroclimatology studies in northern China have focused on linear statistical analysis, but lacking studies based on the process of ring formation to clarify the radial growth of trees. Tree-ring width standard chronology (STD) was established using samples of Larix principis-rupprechtii collected at 2303 m altitude on Luya Mountain. Using the Vaganov-Shashkin (VS) model to simulate growth and development, the internal physiological mechanism of radial growth is identified. It was concluded that: (1) the growing season of L. principis-rupprechtii was May to September; (2) soil moisture was a significant factor in the early and late growing seasons, and temperature was the dominant factor in its main growth period; and (3) formation of narrow ring widths was closely related to drought stress, the development of wide ring widths will be restricted by increasing future temperatures. The VS model is applicable for radial growth simulation of subalpine coniferous forests and for guiding the cultivation of local tree species in the future.

Biodiversity loss is a significant problem at a global scale and may be amplified by climate change. In recent years, coniferous forests have had substantial dieback across Europe due to drought and subsequent bark-beetle outbreaks. As many studies on the consequences of disturbance and subsequent management have focused on natural stands, management implications for managed spruce stands are not well understood, even though such stands are widespread throughout Europe. In this study, beetle taxonomy, conservation value, and community composition are compared among spruce plantations and four post-disturbance management approaches: standing deadwood, lying deadwood, clear cuts, and long-term succession. Diversity and community composition differed significantly among management categories, while different beetle families responded similarly. Intact spruce stands harbored the lowest beetle diversity while the highest taxonomic diversity and conservation value was on clear cuts and stands with lying or standing deadwood. The proportion of forest specialists was highest in successional forests. In summary, different forest management categories harbored distinct beetle communities at the family-, species-, and ecological guild levels. Therefore, post-disturbance management should consider the landscape scale and include different management types. This enhances landscape heterogeneity and thus overall biodiversity but could also mitigate negative impacts of natural disturbances on ecosystem services.

Global warming and frequent extreme drought events lead to tree death and extensive forest decline, but the underlying mechanism is not clear. In drought years, cambial development is more sensitive to climate change, but in different phenological stages, the response relationship is nonlinear. Therefore, the dynamic relationship between tree radial growth and climatic/environmental factors needs to be studied. We thus continuously monitored radial growth of Qinghai spruce (Picea crassifolia Kom.) and environmental factors from January 2021 to November 2022 using point dendrometers and portable meteorological weather stations in the central area of the Qilian Mountains. The relationship and stability between the radial growth of Qinghai spruce and environmental factors were compared for different levels of drought in 2021 and 2022. The year 2022 had higher temperatures and less precipitation and was drier than 2021. Compared with 2021, the growing period in 2022 for Qinghai spruce was 10 days shorter, maximum growth rate (Grmax) was 4.5 μm·d⁻¹ slower, and the initiation of growth was 6 days later. Growth of Qinghai spruce was always restricted by drought, and the stem radial increment (SRI) was more sensitive to precipitation and air relative humidity. Seasonal changes in cumulative radial growth were divided into four phenological stages according to the time of growth onset, cessation, and maximum growth rate (Grmax) of Qinghai spruce. Stability responses of SRI to climate change were stronger in Stage 3 and Stage 4 of 2021 and stronger in Stage 1 (initiation growth stage) and Stage 3 of 2022. The results provide important information on the growth of the trees in response to drought and for specific managing forests as the climate warms.

Latewood width (LWW) indices of trees are considered a reliable proxy of summer precipitation in the Northern Hemisphere. However, the strong coupling and high correlation between earlywood width (EWW) and LWW indices often prevent registration of climate signals of the LWW index. In this study, 328-year-long earlywood width and latewood width chronologies were developed from Chinese pine at two sites in the Hasi Mountains, north central China. The climate responses of these chronologies were analyzed and the LWW index used to derive summer precipitation signals. Correlation analyses showed that LWW was particularly influenced by earlywood growth and recorded stronger climate signals of the previous year as EWW, rather than those of the current year with infrequent summer climate signals. However, after removing the effect of earlywood growth using a simple regression model, the adjusted LWW chronology (LWW_adj) showed a strong relationship with July precipitation in dry years. This suggests that the LWW_adj chronology has the potential to be used to investigate long-term variability in summer precipitation in drought-limited regions.