Accurate individual tree delineation (ITD) is essential for forest monitoring, biodiversity assessment, and ecological modeling. While remote sensing (RS) has significantly advanced forest ITD, challenges persist, especially in complex forest environments. The use of imagery data is compelling given the rapid increase in available high-resolution aerial and satellite imagery data, the increasing need for image-based analysis where reliable 3D data are unavailable, the widening gap between data supply and processing capabilities, and the limited validation of state-of-the-art (SOTA) methods across diverse real-world conditions. This study aims to advance ITD research by evaluating SOTA instance segmentation approaches, including both recently developed and established methods. The analysis evaluates ITD algorithm performance using the largest forest instance-segmentation imagery dataset to date and standardized evaluation protocols. This study identifies key factors affecting accuracy, reveals remaining challenges, and outlines future research directions. Findings in this study reveal that ITD accuracy is heavily influenced by image resolution, forest structure, and method design. Findings also reveal that, while algorithm innovations remain important, robustness and transferability that ensure generalization across diverse environments are what differentiate method performances. In addition, this study highlights that commonly used evaluation metrics may fail to adequately capture precise performance in specific applications, e.g., individual-tree-crown segmentation in this study. Assessment reliability can be strengthened through the adoption of stricter criteria. Future research should focus on expanding datasets, refining evaluation protocols, and developing adaptive models capable of handling varying canopy structures. These advancements will enhance ITD scalability and reliability, contributing to more effective forest research and management at a global scale.

Vertical stratification in forests acts as an ecological filter, driving woody plants to evolve specialized survival strategies. Angiosperms, in particular, develop secondary xylem with three interdependent functions-water transport, mechanical support, and storage. Trade-offs between these functions vary with resource heterogeneity and environmental pressures. Balancing these functions is based on trade-offs in xylem structure, particularly in the xylem space allocation of vessels, fibers, and parenchyma fractions. However, how plants optimize these trade-offs along forest vertical strata remains unexplored. Anatomical methods were used to determine the fractions of vessels, fibers, and parenchyma in the secondary xylem of 119 individuals within a multilayered forest in eastern China. Ternary plots and standardized major axis analyses were employed to evaluate variations in trade-offs between vessel and fiber fractions, and between parenchyma and fiber fractions across different vertical strata. We found that trade-offs in spatial allocation among cell types occur in all vertical strata. For the fiber-vessel trade-off, canopy and understory trees followed a similar pattern, but canopy trees consistently maintained a higher vessel fraction. In contrast, the fiber-parenchyma trade-off was markedly stronger in understory trees. Our results illustrate that forest vertical stratification significantly influences trade-offs in xylem cell allocation, suggesting functional trade-offs of xylem depend on forest strata. These findings will help clarify how trees adapt to stresses associated with vertical forest strata.

Urbanization profoundly reshapes the diversity patterns of urban spontaneous plants, which are effective indicators of urban environmental change. Categorizing ecological species groups (ESGs) are crucial for understanding species-environment relationships and for supporting biodiversity conservation. In this study, 586 spontaneous plants across 16 cities in Yunnan province, China, were classified into four ESGs using a two-way clustering approach that integrates urban-rural gradients (expressed by the distance to city boundary) and human activity intensity (the proportion of impervious surface), and their indicator species were subsequently identified. The four ESGs—disturbance-sensitive urbanphob plants (DSUP, 29.5%), disturbance-tolerant urbanphob plants (DTUP, 26.5%), disturbance-tolerant urbanophil plants (DTUO, 22.9%), and disturbance-sensitive urbanophil plants (DSUO, 21.2%). Trend analysis revealed that only DSUP shows consistent response across both urbanization gradients, suggesting that relying on a single urbanization metric may bias in ESG classification and obscure the complexity of plant responses to urbanization intensity. Functional diversity metrics combined with a null model approach revealed significant trait convergence within ESGs (except DSUO) and clear variability among them, suggesting a convergence in traits driven by urbanization filtering effects. Our findings revealed that indicator species of ESGs are predominantly by herbaceous, native, and autochorous species. Nonetheless, trait variations still emerged along disturbance gradients. In particular, fruit type composition varied substantially among indicator species of ESGs, with caryopsis predominated in DSUP (>60%), pod in DTUP (>25%), capsule and achene in DTUO (25.0% and 20.8%, respectively), and caryopsis (29.4%) and nut (23.5%) in DSUO. Our study emphasizes the difference in species adaptation strategies at different levels of urbanization, underscoring the imperative to develop appropriate habitat conservation strategies that align with species-specific habitat preferences.

Abstract Winter buds play a crucial role in regulating stem and leaf development. However, the cold resistance and their adaptive strategies have not been fully understood. In this study, we examined the morphological (maximum length), biochemical (water content, concentrations of nonstructural carbohydrates, total starch content and total soluble sugar) and physiological (the low semi-lethal temperature, LT50) traits of winter bud across 72 common woody species in a species-rich subtropical evergreen broad-leaved forest in Eastern China. Despite substantial interspecific variation in winter bud traits, total soluble sugar content showed phylogenetic conservation, with closely related species exhibiting similar levels. Evergreen broad-leaved species demonstrated higher cold resistance (lower LT50) than deciduous broad-leaved species, aligning with their resistance rather than avoidance strategies. Scaly buds had stronger cold resistance than naked buds, and bud length and carbohydrate storage were positively associated with cold resistance. At the organ level, the physiological cold resistance of winter buds is positively influenced by both their morphology and carbohydrate storage (concentrations of nonstructural carbohydrates and total soluble sugar), and also positively influenced by the whole plant economics spectrum at the species level. However, the morphological and biochemical traits of winter buds represent another new dimension decoupled from the whole plant economics spectrum. Our findings highlight winter bud traits as a complex but long-neglected functional dimension of species’ adaptive strategies to cope with cold temperatures in evergreen broad-leaved forests, and provides perspectives at different levels (organs and species) for understanding plant adaptations to winter bud growth.

The species pool hypothesis argues that local species diversity mainly depends on regional diversity, which is influenced by dispersal, historical and current environmental conditions. We hypothesize that regional factors, such as the size of the regional species pool, current climate, topographical variability, and historical climate stability, also impact local species-abundance patterns, like the rarity of local species, though their specific effects are not yet well understood. Analyzing data from 3307 species across 3923 forest plots in Chinese subtropical and tropical regions, we employed boosted regression trees and structural equation modeling to assess the roles of regional species pool size along with climatic seasonality, topography, and soil factors, in shaping local richness and rarity. We found that local tree species richness declined with increasing latitude, while species rarity decreased from west to east. The factors such as current regional environment, paleoclimate stability, and human disturbance significantly affected local richness and rarity, primarily through their effects on regional species pool size. The impacts of regional mean temperature and elevational range on local richness surpassed local influences. Conversely, local climatic seasonality exerted the strongest influence on species rarity, followed by human activity. Overall, the findings indicate that regions with large regional species pools tend to support diverse communities with high proportions of rare species.

Urbanization profoundly alters ecosystems, yet urban areas, home to more than half the world’s population, also support a wide range of biodiversity. Urban street trees, a crucial component of urban green space, are among the most frequently encountered green infrastructure in city environments for urban residents. Despite their vast range of benefits to urban quality of life, the taxonomic diversity and phylogenetic diversity patterns at the regional scale, and the underlying drivers, remain insufficiently understood. To address this, we explore and map geographic patterns of taxonomic and phylogenetic diversity of street trees across 116 county-level cities of Yunnan province and further analyze the factors influencing these patterns. Urban street trees comprise 180 species (119 genera, 47 families), with distribution highly uneven (81 species occurring only once and 30 species in over 10 cities). We found that climatic and anthropogenic (i.e., socio-economic and urbanization metrics) factors jointly influenced taxonomic and phylogenetic diversity, with anthropogenic factors primarily driving taxonomic diversity and climatic factors dominating phylogenetic diversity. Although urban expansion can introduce more species, the phylogenetic structure of street trees is still shaped by climate. Enhancing diversity requires introducing climate-resilient species that can adapt to current and future environmental stresses.

Severe droughts induced by climate change present substantial challenges to urban forests. While the role that species richness plays in enhancing drought resistance in natural ecosystems has been highlighted in previous studies, its impact within urban forests remains less understood. Leveraging extensive field-based measurements across 1115 forest patches and 477 tree species in 116 cities in Yunnan Province, China, we found that species richness and forest cover co-regulate drought resistance in urban settings. However, a consistent and significant positive effect of species richness was observed primarily in warm, cloudy, higher-income regions during infrequent dry-season droughts. Urban forests characterized by a higher proportion of non-native and evergreen species also exhibited greater drought resistance. These results underscore the importance of effective management in urban forests to enhance their resilience against extreme drought.

Urbanization and climate change are rapidly altering large-scale plant distributions and local community compositions, profoundly impacting ecosystem functions and services. However, it remains unclear how life form compositions, one of the key functional biodiversity components, respond jointly to urbanization and climate gradients. Here we investigated the life form compositions of 2,864 naturally regenerated spontaneous plant species across 129 cities in Yunnan province of China, a global biodiversity hotspot with diverse environmental condition. Our results showed perennial herbs (45.0%) predominated in urban ecosystem, followed by annual herbs (29.2%) and woody plants (25.8%). Bayesian hierarchical models revealed that as urban expansion, the proportions of annual herbs rise, while the proportions of both perennial herbs and woody plants decline, indicating urban expansion favors short-lived plants but is detrimental to long-lived plants. Increasing mean annual temperature with a decline in perennial herbs and a concurrent increase in woody plants, suggesting divergent adaptive responses to thermal stress. Our results highlight the complex, divergent responses of plant life forms to urbanization and climate change, emphasizing the need for targeted conservation strategies that consider both the resilience of short-lived species and the vulnerability of long-lived plants.

Climate change significantly affects the dynamics of mountain ecosystems, impacting not only species distributions but also their phenological characteristics. Nevertheless, our comprehension of the effects of climate change on biodiversity is still limited, primarily due to insufficient historical data. The dramatic temperature variations over short distances make permanent monitoring plots along elevational gradients an ideal natural laboratory for investigating species’ responses to climate change. Drawing on field survey information gathered from 2018 to 2022, we have developed a bryophyte species-trait dataset that encompasses 16,920 trait measurements across four categories: taxonomy, distribution, resistance traits, and reproductive traits, derived from 549 species in Eastern China. The compilation of this bryophyte species-trait dataset offers valuable opportunities to deepen our understanding of the factors, constraints, and effects associated with biodiversity variability, while also providing richer insights into predicting species distributions and implementing targeted in-situ conservation strategies.

Outdoor heat stress possesses significant health risks, contributing to thousands of premature deaths each summer. Urban greening has been widely recognized as a potential solution to mitigate this heat threat. However, the optimal way to maximize cooling effects from urban forest—specifically through the influences of plant leaf traits and canopy structure on local climate (temperature and humidity)—remains underexplored. To address this issue, we combined traditional forest inventory methods with advanced LiDAR observations to assess 3883 individual trees and 77 plant species in the urban forests of Shanghai during the summer of 2021. For all trees, we analysed six leaf traits: nitrogen content, phosphorus content, potassium content, leaf area, specific leaf area and leaf dry matter content. Additionally, three canopy structural characteristics—mean foliage height, foliage height diversity, and canopy coverage—were investigated. Near‐surface air temperature and relative humidity within and outside the forests were measured repeatedly using a state‐of‐the‐art mobile monitoring system during four time intervals: 07:00–10:00, 11:00–14:00, 16:00–19:00 and 21:00–24:00. Our findings revealed that leaf stoichiometric traits significantly contribute to the variation in cooling effects, with their relative importance being twice as high as that of canopy structure during morning and afternoon periods. Specifically, nitrogen (N) and phosphorus (P) in leaves positively influenced cooling and humidification, whereas potassium (K) had a negative impact. Synthesis and applications . To enhance the summer cooling potential of urban forests, we recommend incorporating tree species with high leaf N, leaf P and low leaf K in urban park designs, rather than solely expanding canopy coverage. This study highlights the importance of considering plant traits in future urban green design, planning and management for combating heat effectively.

Mountains in China are crucial for biodiversity conservation due to unique topography and climate, providing essential habitats and refugia for many plant species. Standardized open datasets along elevational gradients across multiple mountains remain limited. Here we used standardized field protocols to collect plant diversity data of 370 permanent sampling plots along elevations in 17 mountains. Species identity and abundance of all woody plants with ≥ 1 cm diameter at breast height were recorded. We calculated species-level basal area, abundance, and relative importance value for all plants, and separately for two vegetation layers. The dataset spans 46° longitude, 24° latitude, ranges from 166 to 3,835 m a.s.l., and includes 1,493 species from 121 families and 450 genera. It covers nearly all major ecosystems from tropical rainforests to tundra, providing baseline data for studying plant diversity changes along elevations and latitudes. This dataset enables direct comparisons across mountains, helping evaluate impacts of climate and land-use changes on species range shifts and ecosystem transitions, and inform conservation strategies for mountain ecosystems.

As a widely disseminated world religion, Buddhism's selection of religious species may profoundly impact candidate species distribution. This study sampled 246 Chinese temples covering diverse regions to investigate the selection modes of Buddhist tree species (BTS) and the alien religion's influence on Chinese indigenous biodiversity and spread. In species selection at the national scale, anthropogenic factors were less important for BTS's taxonomic, phylogenetic and religious‐use spectrum. Bioclimatic factors, especially the minimum temperature of the coldest month, were the dominant drivers. During the trans‐climatic‐zone dissemination of Buddhism in China, the growth of original BTS (OBTS) from the India source area was stifled outside tropical and subtropical zones. The climatic constraints demanded the recruitment of substitute BTS (SBTS) from the indigenous flora. The same suite of religious uses was assigned to different BTS through the substitution process. With a weak environmental filter, indigenous species with close phylogenetic relationships and morphological similarity to OBTS were preferentially selected as substitutes. However, under a strong environmental filter, the selection was compelled to favour indigenous species with a distant phylogenetic relationship but similar part‐specific organ morphology (leaf or fruit) to OBTS. Ultimately, Buddhism, as an alien religion, influenced indigenous biodiversity mainly by localizing BTS and facilitating their spread and preservation. Read the free Plain Language Summary for this article on the Journal blog.

PREMISE:Parenchyma is an important cell type in the secondary xylem of angiosperm trees, with considerable variability in its abundance. However, the functional significance of these variations and their roles in plant ecological strategies is poorly understood at the inter- and intraspecific levels. METHODS:For this study, fractions of axial parenchyma cells (AP) and ray parenchyma cells (RP) in xylem tissue were quantified for 156 individuals of 45 tree species along an elevational gradient from 600 to 1600 m a.s.l. in eastern China. Environmental factors and height of sampled trees at each sampling site were also measured. Linear mixed models were employed to assess the relative extent of both intraspecific and interspecific variations in parenchyma cells in xylem tissue fractions and to identify intraspecific variations along environmental gradients (e.g., temperature and humidity) and tree heights. RESULTS:Interspecific variations explained the large diversity in AP fractions. Conversely, intraspecific variations accounted for ~50% of the overall variations in RP fractions. Further, intraspecific variations in the RP and the total AP and RP fractions exhibited negative correlations with tree heights but showed no significant relationship with climate. CONCLUSIONS:Intraspecific variations in parenchyma cells in xylem tissue fractions are not necessarily an adaptation or acclimation to changes in the environment but are coordinated with tree heights.

Resilience to drought represents an important focus for trees during climate change, with the aim of predicting the resistance and recovery of species worldwide. Previous studies mainly linked tree growth resilience to plant functional traits that are related to resource acquisition and investment. Here, we investigate a potential link between resilience and the amount of parenchyma tissue in wood, a multifunctional tissue that may provide various physiological benefits to drought-related mechanisms. We compiled a global tree-ring data set to evaluate the relationship between growth resistance, resilience or recovery from drought and xylem parenchyma tissue fractions of 50 angiosperms, which was complemented with a local study of nine species from Mt. Tiantong in China. We also assessed the influence of climate and phylogeny on these relationships. We found that growth recovery after drought was positively related to the fractions of total parenchyma locally and globally. This association remained statistically significant when accounting for the effects of climate and phylogeny. No other associations between parenchyma fractions and growth resilience metrics were statistically significant. Our results suggest that drought recovery of angiosperm trees is affected by the amount of parenchyma. Incorporating xylem parenchyma fraction with other traits, such as hydraulic traits, could therefore enhance our comprehension of how various angiosperm tree species will respond to future droughts. Further studies should focus on unravelling the physiological roles of xylem parenchyma fraction.

Spontaneous plants, those not planted by people or remaining from before urbanization, are vital to urban biodiversity. Their distribution in urban systems is affected by seed dispersal mode and environmental factors such as natural dispersal limitation and habitat quality factors. We assessed four seed dispersal modes in 16 cities in Yunnan province, the most biodiverse province in China. Autochory, in which plants eject seeds or otherwise power their seeds’ dispersal, was the dominant seed dispersal mode of urban spontaneous plants in most cities (13 out of 16), whereas hydrochory, or passive seed dispersal by water, was the least frequent. Our research showed spontaneous plants in urban ecosystems adopt convergent strategies to address environmental stressors. The number of urban plants was significantly higher in colder and more-humid climates but decreased with increased dispersal limitations and reduced habitat quality. Sensitivities to these factors varied, with autochory especially sensitive to dispersal limitation and hydrochory sensitive to habitat quality and climate. Findings suggest improving habitat quality and creating green corridors would enhance conservation efforts for urban biodiversity. Plants are vital to healthy cities, yet urban environments filter the plant traits we find. This study assesses the relative dominance of different seed dispersal modes among plants that establish in cities without human intent, finding that many disperse their own seeds and that seed dispersal by water is less common.

Vegetation science research has been conducted for approximately 200 years; however, until now there has not been a unified classification principle or system that was acceptable to vegetation scientists. To facilitate the development of vegetation science and its applications in natural conservation, a unified vegetation classification system is urgently required. Here we propose a unified eco-physiognomic-floristic vegetation classification system (EcoFloVCS) that combines eco-physiognomic and floristic characteristic classification systems. Under the EcoFloVCS, plant communities are considered to have six key components (species composition, structure, habitat, development, locality, and function). Six associated characteristics are derived from these six components (dominant species, diagnostic species, physiognomy, distribution patterns, dynamics, and disturbance processes). These characteristics are used as the basis for community classification. The high-level units of this system agree with the UNESCO system, whereas the middle- and low-level units correspond to the Braun-Blanquet classification system. Both are connected by a Division (Subformation) unit. Based on the EcoFloVCS, a vegetation system was constructed for the four highest units worldwide that included seven Formation Classes, 22 Formation Subclasses, 39 Formation Groups, and 119 Formations. We assume that vegetation science will benefit from our unified EcoFloVCS through comparing and understanding community structures and functions on a global scale.

Beta diversity patterns along environmental gradients and underlying mechanisms constitute key research inquiries in biogeography. However, ecological processes often also influence the functional traits of biological communities, making the assessment of functional beta-diversity crucial. Ground beetles (Coleoptera: Carabidae) are one of the most species-rich groups in the insect community, displaying strong habitat specificity and morphological differences. In this study, we explored the patterns of taxonomic and functional beta diversity in ground beetle communities along the altitudinal gradient of warm-temperature forests. By partitioning beta diversity into turnover and nestedness components, we evaluated their relationship with spatial distance. Our findings indicate a decline in species and functional trait similarity with increasing elevation and geographic distance. Further analysis attributed both types of beta diversity in carabids to a combination of dispersal limitation and environmental filtering, with elevation and geographic distance emerging as significant factors. Interestingly, forest-type variations were found to have no impact on the beta diversity of these communities. Our study reveals the impact of environmental filtering and dispersal limitation on both taxonomic and functional beta-diversity, shedding light on carabid community assembly in localized warm-temperature forest areas in eastern China. In this study, we investigate the taxonomic and functional beta diversity patterns of ground beetle communities along the altitudinal gradient of warm-temperature forests in eastern China. We get the conclusion that dispersal limitation and environmental filtering jointly drive the taxonomic and functional beta-diversity of ground beetles. This study provides insight into carabid community assembly in Chinese warm-temperature forests.image

Spontaneous plants are crucial components of urban biodiversity. The distribution of spontaneous plants can be profoundly affected by their seed dispersal mode and environmental factors in urban systems. Since a comprehensive investigation into the drivers of successful seed dispersal modes of spontaneous plants is still lacking, we explored the impacts of natural factors, dispersal limitation, and habitat quality factors on the diversity pattern of spontaneous plants. We assessed the diversity patterns of four seed dispersal modes in 16 major cities in Yunnan province, the most biodiverse province in China. A total of 1,744 spontaneous plants of 916 genera and 175 families were recorded in 893 green patches. The dominating seed dispersal mode of urban spontaneous plants in most cities (13 out of 16) was autochory (33.5–38.7%), with hydrochory being least frequent (4.3–10.9%). Our research highlights spontaneous plants in heavily disturbed anthropogenic ecosystems, such as urban areas, tend to adopt convergent strategies to address environmental stressors. Their richness was significantly higher in colder and humid climates. However, as dispersal limitations (measured by distance to city boundary, city size and urbanization rate) increased and decrease in habitat quality (as expressed by patch area), the richness of all dispersal modes experienced a reduction. However, the sensitivities among different dispersal modes to these factors are divergent. Hydrochory exhibited the strongest sensitivity to habitat quality and climate factors. Whereas autochory demonstrated a strongest sensitivity, and anemochory showed a weakest sensitivity to dispersal limitation. These results suggest that include improving habitat quality or creating green corridors to mitigate dispersal limitation between urban areas and surrounding mountains will be valuable additions to urban biodiversity conservation efforts.