Aims Plant functional traits reflect the trade-off mechanism for resource acquisition, and plants can be classified as resource-acquisitive and resource-conservative based on their trait combinations. Nitrogen (N) is essential for plant growth, and increased N deposition can affect plant traits and resource acquisition strategies by altering the ecosystem N cycle. However, most studies on the effects of N deposition on plant traits and strategies have focused on the tree layer, with relatively little research on understory plant communities, especially in boreal forests.

Methods This study relied on a thirteen-year of N addition experiments in Larix gmelinii forests to explore the effects of N addition on understory plant traits at the species and community levels, and to analyse changes in plant resource use strategies.

Important findings The results showed that N addition promoted plant height, specific leaf area and relative cover of acquisitive species (e.g. Betula fruticosa and Deyeuxia angustifolia), while it suppressed the plant height, relative cover and photosynthetic rate of conservative plants (e.g. Vaccinium vitis-idaea), suggesting that N addition favoured the growth of plants with acquisitive strategies. At the community level, N addition significantly promoted leaf N content, specific leaf area, and plant height; and significantly reduced leaf phosphorus content in community-weighted mean traits, and these changes were mainly caused by intraspecific variation. In contrast, N addition did not significantly change the functional dispersion of most traits, and these changes were mainly related to interspecific variation. More importantly, the changes in community traits reflect that N addition has shifted in the resource use strategy of boreal forest understory plant communities from conservative to acquisitive. In summary, this study reveals how long-term N addition changes resource use strategies of boreal forest understory plant communities and their relationship with plant community composition and growth response.

Aims Insect herbivory leads to leaf damage in subtropical forests, but it remains unclear whether nitrogen (N) and phosphorus (P) additions alter the insect resistance of saplings. This study focused on the saplings of six dominant tree species in the evergreen broad-leaved forest of Jiulian Mountain, Jiangxi Province. An eight-year N and P addition experiment was conducted to examine the effects of these nutrients on insect resistance. We measured leaf herbivory damage rate, stoichiometric ratios, mechanical resistance, and chemical resistance under different treatments.

Methods In this study, we conducted an eight-year N and P addition experiment in an evergreen broad-leaved forest in Jiulianshan, Jiangxi Province to determine effects of N and P on the saplings of six dominant tree species leaf herbivory damage, leaf stoichiometry, mechanical resistance, and chemical resistance of saplings.

Important findings Saplings exhibited strong resistance to herbivory, with an average leaf damage rate of 5.4%, which was neither affected by N addition, nor by P addition nor by both. However, significant interspecific differences were found, with light-demanding species showing significantly higher damage rates than shade-tolerant species. N addition and combined N and P addition significantly increased leaf nitrogen concentration per unit mass but did not significantly alter leaf stoichiometric ratios. P addition significantly increased leaf phosphorus concentration and decreased the carbon-to-phosphorus ratio. Both N addition and P addition showed no significant changes in leaf mechanical resistance such as force to tear and force to punch. In contrast, N addition significantly increased amino acid content, and P addition elevated total phenolics content, while tannin levels remained stable. Notably, light-demanding species exhibited higher damage due to higher leaf N concentration, whereas shade-tolerant species exhibited lower damage due to stronger mechanical resistance and chemical defense. These findings suggest that saplings in subtropical forests maintain high resistance to background insect herbivory pressure through stable physical defenses and flexible chemical defenses, potentially enhancing the ecological stability of natural regeneration within the context of global change.

Aims Elevated atmospheric ozone (O₃) concentrations significantly affect plant nutrient allocation, thereby regulating litter decomposition. However, the stoichiometric responses of leaf and fine root litters to O₃ stress remain unclear. This study aimed to investigate how elevated O₃ influenced the dynamics and regulatory mechanisms of carbon (C), nitrogen (N), and phosphorus (P) stoichiometry during the decomposition of leaf and fine root litter.

Methods A 12-month decomposition experiment was conducted using Koelreuteria paniculata and Camellia sinensis at the O₃-FACE platform in Yanqing, Beijing. We applied two treatments i.e., ambient air (NF) and elevated O₃ (NF60, ambient air + 60 nmol·mol^-1 O₃). At four decomposition stages (0, 1, 3, and 12 month), we measured litter C, N, and P concentrations and stoichiometric ratios (C:N, C:P, N:P).

Important findings Elevated O₃ concentration significantly altered the initial stoichiometric structure and residual characteristics of the litter. Under NF60, the initial C:N ratio of K. paniculata leaves increased by 7.6%, while N:P decreased by 17.7%, leading to a 10.3% increase in mass remaining after 12 months. In C. sinensis fine root litter, phosphorus (P) concentration increased by 11.1% and the C:P ratio decreased by 14.5%, showing organ- and species-specific stoichiometric shifts. Litter mass remaining (%) was significantly correlated with C:N, C:P, and N:P ratios. During decomposition, the N:P ratio of leaf litter increased significantly in both species (K. paniculata: 43.6%-68.0%; C. sinensis: 52.9%-59.3%), indicating enhanced P limitation in the later stages. Consistent with the microbial growth rate hypothesis, fine root litter also exhibited organ-specific increases in N:P, but the magnitude and treatment effects depended on species. O₃ altered litter stoichiometric characteristics, particularly C:P balance, which may have influenced microbial nutrient acquisition and contributed to slower carbon turnover; moreover, leaf litter and fine roots showed distinct response patterns. Leaves and fine roots exhibited contrasting responses: K. paniculata leaves were more constrained by P availability, while C. sinensis fine roots maintained higher decomposition efficiency through enhanced P redistribution. These findings highlight organ-specific adaptive strategies under O₃ stress and provide novel insights into stoichiometric regulation of litter decomposition under global change.

Aims Previous studies have shown that different stages of growing season and twig ages are the key factors influencing variation in plant twig traits. However, few studies have simultaneously investigated how twig traits and their relationship shift in response to changes in growing season stages and twig ages.

Methods In this study, Pinus koraiensis, Picea koraiensis, and Abies nephrolepis, typical evergreen conifers in northeast China, were studied. We measured seven twig traits in 135 trees across three growing season stages (early: July; middle: September; late: November): specific twig length (STL), twig dry matter content (TDMC), twig wood density (TWD), pith proportion cross-sectional area ratio, xylem proportion cross-sectional area ratio, phloem proportion cross-sectional area ratio and resin channel proportion cross-sectional area ratio. Both annual and perennial twigs from these trees were analyzed to explore how twig traits and their correlations change throughout seasonal progression and with twig aging.

Important findings In the early growing season, twig dry matter content and twig wood density were significantly lower than those in the middle and late stages. Xylem proportion cross-sectional area ratio and phloem proportion cross-sectional area ratio increased significantly with twig age. The negative correlation between specific twig length and twig dry matter content was only observed in the early growing season. Notably, annual twigs displayed a “quick investment-return” survival strategy characterized by high specific twig length and low twig dry matter content in the early season, contrasting with the “slow investment-return” survival strategy in the late growing season and perennial twigs. Our findings provide insight into how plants adapt to habitat changes by regulating twig traits.

Aims Exploring the differences in the life strategies of the “twig system” (old twig, new twig and leaf) of Corylus mandshurica in different seasons can provide a theoretical basis for the protection and management of wild C. mandshurica. At the same time, it can promote the understanding of the multi-organ coordinated response of plants to climate change.

Methods In this study, taking the dominant species in the shrub layer of the broad-leaved Korean pine forest, C. mandshurica, as an example, nine traits including carbon, nitrogen, phosphorus, soluble sugar, starch, total non-structural carbohydrates, total phenol, tannin and flavonoid contents in the old twigs, new twigs and leaves of C. mandshurica were measured in three seasons, namely spring (May), summer (July) and autumn (September).

Important findings The results showed that, except that the effect of the organ on starch was not significant, the season, the organ and their interaction had a relatively significant effect on the functional traits of C. mandshurica. In spring and summer, the contents of total phenol and tannin in the old twigs were relatively high, while in autumn, the contents of soluble sugars and other substances were relatively high. In spring, the nitrogen content in the new twigs was relatively high, while in summer and autumn, the contents of total non-structural carbon, tannin, flavonoid and other substances in the new twigs were relatively high. In spring and summer, the nitrogen and phosphorus contents in the leaves were relatively high, while in autumn, the contents of flavonoid and other substances in the leaves were relatively high. In addition, in spring and summer, compared with the new twigs and old twigs, the trait correlation network of the leaves was more complex; in autumn, the situation was the opposite. This reflects that in the “twig system” (old twig, new twig and leaf) of C. mandshurica, in spring, the leaves and new twigs tend to adopt a “growth” strategy, and the old twigs tend to adopt a “defense” strategy; in summer, the leaves tend to adopt a “growth” strategy, while the new twigs and old twigs tend to adopt a “defense” strategy. In autumn, the leaves tend to adopt a “defense” strategy, and the new twigs and old twigs tend to adopt a “resource recycling” strategy. The research results reveal that there are differences in the growth and defense strategies of the “twig system” of C. mandshurica, which is conducive to promoting the theoretical research on how plants respond to environmental changes towards the direction of systematization and refinement.

Aims As a dominant and keystone species in temperate coniferous forests of China, Pinus tabuliformis exhibits strong environmental adaptability. Investigating the stoichiometric characteristics of leaves, twigs and roots in both current-year (newly developed) and perennial (≥1 year old, mature) organs, as well as their relationships, is essential for understanding intraspecific variation and plant resource allocation strategies.

Methods This study was conducted in natural P. tabuliformis forests across nine regions in China. A total of 81 individual trees were sampled to measure the carbon (C), nitrogen (N) and phosphorus (P) content in their six organs (current-year leaves, perennial leaves, current-year twigs, perennial twigs, absorptive roots and transport roots).

Important findings (1) Current-year organs exhibited higher N and P contents but lower C:N, C:P, and N:P ratios compared to perennial organs. Stoichiometric traits showed considerable intraspecific variation across organs of different ages, with organ age identified as the primary factor influencing these differences. (2) Standardized major axis analysis revealed that perennial leaves had higher P content per unit mass than current-year leaves, whereas current-year twigs and absorptive roots showed higher C, N and P contents than their perennial counterparts (perennial twigs and transport roots). (3) Additionally, absorptive roots had significantly higher C, N and P contents per unit mass than both current-year leaves and twigs. (4) Redundancy analysis indicated that the main environmental drivers of stoichiometric traits in current-year and perennial leaves were mean annual temperature and soil P content, respectively. The most significant environmental factors affecting the stoichiometric traits of current-year and perennial twigs were annual precipitation and soil P content, respectively; while the main environmental factors influencing absorptive and transport roots were soil moisture and soil N content, respectively. This study reveals the resource allocation strategies and environmental adaptability of leaves, twigs, and roots across different age classes in P. tabuliformis. The findings demonstrate that the studies on the stoichiometry of evergreen species should fully consider age-related differences among organs, which is essential for elucidating their nutrient allocation strategies and environmental adaption mechanisms.

Aims Clarify the variation patterns and corresponding response mechanisms of plant functional traits and carbon-nitrogen stoichiometry in artificial plantations of different tree species under the age gradient.

Methods In this study, Populus tomentosa, Platycladus orientalis and Styphnolobium japonicum at different ages were selected as the research objects to determine and explore the changes and relationships of different organ functional traits, carbon-nitrogen stoichiometry and soil physicochemical properties.

Important findings (1) With the increase of forest age, the content of soil nutrients, clay and silt of different tree plantations increased significantly. While soil total phosphorus content of Populus tomentosa plantations, and soil pH value of Platycladus orientalis plantations decreased. (2) The specific leaf area of different tree species increased significantly with the increase of forest age, while the specific leaf mass decreased significantly. The root carbon content (average 36.25%) was lower than that of branches (45.52%) and leaves (44.83%), and the leaf nitrogen content (1.98%) was higher than that of roots (1.30%) and branches (0.64%). With the increase of forest age, the nutrient content and carbon-nitrogen ratio of different organs varied with tree species. (3) The functional traits of Populus tomentosa plantations of different organs were coordinated, while the functional traits of leaves and roots of Platycladus orientalisplantations evolved independently, forming a decoupling strategy. (4) The increase of soil water content and the improvement of soil texture are important reasons for the changes in plant traits. (5) The soil total nitrogen content was significantly negatively correlated with the carbon content in leaves and roots. Redundancy analysis showed that soil electrical conductivity significantly affected plant functional traits. (6) Random forest analysis showed that the significant factors affecting the carbon-nitrogen ratio of leaves, branches and roots included soil total phosphorus and clay contents, specific leaf area, leaf dry matter mass and plant nutrient content. The research results reveal the differences in plant functional traits and organ carbon and nitrogen distribution among different tree species under the forest age gradient, enriching the theoretical framework of the plant economic spectrum.

Aims Mycorrhizal fungi are closely related to the host’s carbon (C), nitrogen (N), phosphorus (P) concentrations, and C, N, P stoichiometric characteristics. However, whether the C, N, P stoichiometric characteristics in leaves and fine roots of different mycorrhizal tree species are significantly correlated in subtropical forests remains unclear. This study collected leaf and fine root samples of 81 arbuscular mycorrhizal (AM) tree species and 16 ectomycorrhizal (ECM) tree species from the forest dynamic monitoring sample plot in Heishiding Nature Reserve, located in Guangdong Province, and measured their C, N, and P concentrations to clarify the differences of the C, N, P stoichiometric characteristics in leaves and fine roots between AM and ECM tree species, and whether the C, N, P stoichiometric ratio in leaves and fine roots of AM and ECM tree species changes consistently.

Methods We calculated Blomberg’s K statistic to test phylogenetic signals, used the linear mixed model to test the differences in C, N and P concentrations and stoichiometric ratios of leaves and fine roots among different mycorrhizal species, and used the Pearson correlation coefficient to test the correlation between C, N and P concentrations and stoichiometric ratios in leaves and fine roots of different mycorrhizal species. Finally, we used standardised major axis regression to analyze the relationship of C, N and P concentrations and stoichiometric ratios between leaves and fine roots in different mycorrhizal species.

Important findings The P concentration in fine roots of AM species was higher than that of ECM species, but C:P was lower than that of ECM species. There was a significant positive correlation between the N and P concentrations, C:N and C:P in the leaves and fine roots of AM and ECM tree species. There was a significant correlation between the concentrations of C, N and P and stoichiometric ratios of leaves and fine roots in AM species, while there was a significant correlation between N concentration, C:N and N:P of leaves and fine roots in ECM species. The results of this study confirm that the colonization of mycorrhizal fungi affected the chemical element composition and stoichiometric ratio of plants, but the C, N and P stoichiometric ratios between leaves and fine roots in AM and ECM tree species were all significantly correlated.

Aims The reabsorption of nitrogen (N) by leaves can reduce the tropical and dependence of root systems on soil N after the decomposition of fallen leaves. However, whether N reabsorption efficiency is dependent on the N contents in fresh leaves and in soils remains poorly understood, and whether this coupling varies with life forms is also largely unknown.

Methods Here we collected fresh and senescent leaves of 92 woody plants in tropical and subtropical forests in southern China and complied a global dataset of N reabsorption efficiencies from 54 literatures to evaluate the coupling of N reabsorption efficiency with N contents in fresh leaves and in soils across various life forms.

Important findings We found that: 1) In tropical and subtropical forests and on the global scale, there was no significant difference in leaf N reabsorption efficiency between evergreen and deciduous and between angiosperms and gymnosperms species. On the global scale, the leaf N reabsorption efficiency of trees was significantly greater than that of shrubs, and the efficiency of ectomycorrhizal woody plants was significantly higher than that of arbuscular mycorrhizal woody plants. 2) The N reabsorption efficiency of evergreen woody plants, trees and shrubs was significantly correlated with the initial nitrogen content of leaves, while that of angiosperms and gymnosperms, as well as arbuscular mycorrhizal and ectomycorrhizal woody plants, was not significantly correlated with the initial nitrogen content of leaves. 3) The N reabsorption efficiencies of evergreen, angiosperms and ectomycorrhizal woody plants were significantly correlated with soil N content at the sampling sites, while those of deciduous, gymnosperms and arbuscular mycorrhizal woody plants were not significantly correlated with the soil N content. Our results suggest that there are differences in N reabsorption efficiency among woody plants with different life forms. These differences are primarily influenced by nutrient acquisition strategies, which is of great significance for revealing the differentiated nutrient utilization strategies among plants.

Aims The objective of this study was to determine whether leaf stoichiometry is predominantly shaped by habitat filtering or phylogenetic conservatism in the extreme dry-hot valley of the Jinsha River. We further evaluated the applicability of the biogeochemical niche and stoichiometric plasticity hypotheses at a regional scale.

Methods We collected 240 leaf samples from 13 shrub and herbaceous species at 5 sampling sites along the Jinsha River. Leaf carbon (C), nitrogen (N), and phosphorus (P) stoichiometric traits were measured. Corresponding soil physicochemical properties were also analyzed. Bayesian phylogenetic linear mixed models were used to quantify the relative contributions of habitat factors and phylogeny to variation in leaf stoichiometry, and to explore how major habitat gradients regulate plant nutrient use strategies.

Important findings Habitat factors collectively explained 1.9% to 13.7% of the variability in leaf elements and their stoichiometric ratios. Elevation was the primary driver of leaf C and P concentrations and of C:P and N:P, whereas soil pH was the main regulator of leaf N concentration and C:N. Importantly, significant phylogenetic signals were observed in leaf N and P concentrations, as well as in C:N and C:P, indicating the conservatism of these traits. In addition to phylogenetic constraints, we found that leaf C concentration was primarily associated with plant life form and N:P showed greater intraspecific plasticity. In conclusion, regional leaf stoichiometric patterns were governed mainly by phylogenetic conservatism and refined by phenotypic plasticity. These findings enhance our understanding of how plant diversity is maintained under habitat stress and broaden knowledge of plant nutrient-use strategies at regional scales.

Aims The stoichiometric characteristics of plant leaves are closely linked to their physiological and ecological functions, such as photosynthesis and water-use efficiency. Among tree species within the same habitat, variations in leaf stoichiometry reflect distinct strategies for utilizing environmental and nutritional resources. In China’s Saihanba region, extensive plantations of Larix gmeliniivar. principis-rupprechtii and Pinus sylvestrisvar. mongholica exhibit declining productivity and weakened ecosystem services, largely due to a lack of theoretical knowledge to inform traditional nutrient management. The objective of this study was to clarify the adaptive divergence and driving factors controlling the nutrient-use patterns of the dominant species used for afforestation projects and to use this knowledge to provide scientific guidance for tree species selection and ecosystem enhancement in semi-arid regions.

Methods We established permanent field plots in the Saihanba region and collected leaf and soil samples from both dominant species in these plots to measure their carbon (C), nitrogen (N), and phosphorus (P) content. We used Redundancy analysis (RDA) and mixed-effects models to identify key environmental drivers of variations in their leaf stoichiometry.

Important findings 1) Total soil C, N and P contents in the L. gmeliniivar. principis-rupprechtii forest were higher than those in the P. sylvestris var. mongholica forest. The total N and P contents in the leaves of L. gmeliniivar. principis-rupprechtii, as well as the intraspecific variation in N-related nutrient stoichiometric ratios, were all higher than those of P. sylvestris var. mongholica, while the leaf C content was lower than that of P. sylvestris var. mongholica; 2) In terms of the environmental factors driving the stoichiometric characteristics of leaves, the influence of soil nutrient content surpassed that of atmospheric variables. Total soil C content accounted for 57.39% of the variation, followed by the mean annual air temperature, which explained 15.77% of the variation; 3) With rising mean annual air temperature, leaf P content of L. gmeliniivar. principis-rupprechtiidecreased and leaf C:P and N:P ratios increased significantly. These findings suggest that P. sylvestris var. mongholica adopts a “conservative strategyˮ by maintaining relatively stable leaf N and P concentrations and constant N:P ratios as an adaptation to low-resource environments, while L. gmeliniivar. principis-rupprechtii employs an “active/acquisition strategyˮ characterized by higher N, P concentrations and flexible C:P and N:P ratios responsive to environmental shifts. This study elucidates the stoichiometric divergence between the two tree species, offering a theoretical foundation for future experiments on nutrient regulation and mechanistic exploration of their eco-physiological processes.

Aims Ziziphus jujuba is a typical xerophytic shrub. Clarifying the variation of its root functional traits and the relationships between root traits and soil properties can enhance the understanding of plant resource-acquisition strategies and provide a scientific basis for the sustainable management of Z. jujuba shrub.

Methods This study selected 24 Z. jujuba populations in different habitats in the Lincheng County, Xingtai City, which is the genuine medicinal material producing area of Ziziphi Spinosae Semen, as the research objects. The morphological, architectural, and chemical traits of Z. jujuba roots and soil properties were measured and analyzed to clarify the root economics space of Z. jujuba and the relationships between root traits and environmental factors.

Important findings (1) The variation in the architectural traits (i.e., branching ratio and branching intensity) of Z. jujuba was significantly higher than that in morphological (i.e., root diameter and specific root length) and chemical (i.e., root nitrogen and carbon content) traits. At the intraspecific level, there was a two-dimensional root economics space for the root functional traits of Z. jujuba. The first dimension was dominated by the trade-off between specific root length/ specific root area and root diameter/ tissue density, representing the transition of root resource-acquisition strategy from autonomous foraging (i.e., developing higher specific root length and specific root area) to mycorrhizal cooperation. The second dimension was composed of negatively correlated root tissue density/diameter and root nitrogen/carbon content, representing the trade-off dimension between root defense and resource acquisition. (2) Soil environments affected the resource acquisition of Z. jujuba roots. In soil with higher total phosphorus, total potassium or sand content and lower pH, water content or organic carbon content, Z. jujuba roots tended to adopt an autonomous foraging strategy. On the contrary, Z. jujuba roots tended to adopt a mycorrhizal cooperative strategy for resource acquisition. (3) Redundancy analysis showed that soil water content (9.29%), total phosphorus content (6.12%), silt content (3.87%), and clay content (2.96%) were the main environmental factors affecting the variation of Z. jujuba root traits. Specific root length and specific root area of Z. jujuba were increased to acquire resource under dry conditions, and root diameter was increased to enhance its adaptability in low-phosphorus environments. There was a balance between resource acquisition and survival defense of Z. jujuba through the synergistic adjustment of root traits. And its resource strategy was driven by both environmental heterogeneity and long-term evolutionary selection.

Aims Urban forests serve as ecological barriers that mitigate urban heat island effects and enhance ecosystem services, attracting increasing attention to their structure and function. Functional traits are essential for characterizing plant ecological strategies and revealing their regulatory effects on ecosystem processes. Most existing studies have focused on natural ecosystems, while the ecological strategies and functional roles of dominant tree species in urban forests remain poorly understood.

Methods This study focused on six key species (Robinia pseudoacacia, Eucommia ulmoides, Styphnolobium japonicum, Acer truncatum, Pinus tabuliformis, and Ginkgo biloba) in Beijing plain forests. Four categories of leaf functional traits, including morphological, elemental, chemical defense, and hydraulic traits, were measured to elucidate interspecific differences in ecological strategies and to characterize the network structure of leaf functional traits.

Important findings Significant interspecific differences in leaf functional traits and corresponding ecological strategies were found: Pinus tabuliformis exhibited the lowest specific leaf area and lowest water potential at turgor loss point, reflecting a strategy that prioritizes resource conservation and drought resistance; Acer truncatum showed high specific leaf area and the highest total phenolic content, representing a strategy of rapid resource acquisition with strong chemical defense; Robinia pseudoacacia had the highest leaf nitrogen content with moderate total phenolic levels, indicating fast growth with basic chemical defense as a strategy; Styphnolobium japonicum possessed the highest phosphorus content and lowest total phenolic content, suggesting a strategy of rapid growth with low chemical defense investment; Eucommia ulmoides displayed high leaf dry matter content and carbon concentration, reflecting moderate resource conservation and investment in structural defense; Ginkgo biloba exhibited intermediate-low values in growth-defense traits, representing a balanced growth with low chemical defense strategy. The leaf trait network constructed from the six species (edge density = 0.37, diameter = 4, average path length = 1.90, clustering coefficient = 0.59, modularity = 0.26) revealed a relatively simple structure, with specific leaf area acting as the central hub connecting different functional modules. This pattern reflects an initial stage of functional differentiation under the “fast-growth and high-efficiency” management orientation of Beijing plain forests, while also implying potential ecological vulnerability. Overall, this study provides new insights into the functional positioning of urban forest species and offers a theoretical basis for enhancing the multifunctionality of plain forests.

Aims Tropical and subtropical areas are hotspots for the distribution of artificial forests in our country. Clarifying the status and influential factors of plant biomass in typically mixed artificial forests in these areas is important. This can help to uncover the limiting factors for stand productivity and guide the management of artificial forests.

Methods In this study, we selected a conifer-broadleaf mixed forest in Yunyong forestry station located in Foshan, Guangdong. This forest was transformed from a Chinese fir plantation. First, we compared the difference in biomass of each plant organ among tree species configuration modes at the early recovery stage (8-16 a). Second, the shifts in soil physicochemical properties and community-level plant functional traits under different conditions of tree species configuration were characterized. Finally, we explored the relative contributions of tree species configuration, soil properties and plant leaf traits to variations in plant biomass, and evaluated their influential pathways. Based on these analyses, we aimed to evaluate the key influential factors for plant biomass in artificial forests in south subtropical areas.

Important findings Our results showed that both plant and organ biomass differed significantly under different tree species configuration modes. Tree species configurations affected plant biomass mainly via regulating leaf functional traits and soil nutrient content. Moreover, leaf functional traits had greater influence on foliage and branch biomass, while the variation in soil nutrient content was the main factor driving the changes in truck, roots and total plant biomass. Specifically, tree species configurations characterized by a higher ratio of leaf nitrogen (N) : phosphorus (P) and a higher functional diversity had greater biomass in plant communities. An increase in soil total P content significantly promoted the increase in plant biomass, while an excess in soil total potassium would suppress the growth in biomass. This study compared the relative effects of leaf functional traits and soil nutrient content on plant biomass in the typically mixed artificial stands in south subtropical forests, and explored the key influential factors for the biomass in total and in each organ. These results provided the theoretical bases for restoration, operation and management of the artificial forests in south subtropical areas.

Aims The study of plant functional traits in response to nitrogen deposition and warming is crucial for understanding plant growth and community assembly under environmental change. However, the differential effects of nitrogen addition and warming on community traits, as well as the underlying mechanisms, remain unclear.

Methods This study was conducted in the Bayanbulak Grassland, located in the southern Tianshan Mountains. We set up an experimental design with warming (open-top chambers, OTC) and nitrogen addition (10 g·m^-2), and measured the effects of nitrogen addition and warming on community species composition and five functional traits (plant height, leaf area, leaf carbon content, leaf nitrogen content, and leaf phosphorus content). The aim was to explore the impact and mechanisms of nitrogen addition and warming on community-level functional traits.

Important findings 1) Compared to the control treatment, nitrogen addition significantly increased community-level plant height and leaf carbon content by 52.89% and 28.65%, respectively, while leaf phosphorus content decreased significantly by 32.23%. There were no significant changes in leaf area or leaf nitrogen content. For plant height, the relative contribution of species turnover to the community change was greater than that of intraspecific trait variability (ITV), whereas for leaf chemical traits (leaf carbon content, leaf nitrogen content, and leaf phosphorus content), ITV played a significantly larger role than species turnover. 2) Under warming, community-level leaf area, leaf nitrogen content, and leaf phosphorus content decreased significantly by 44.53%, 25.07%, and 42.06%, respectively, compared to the control. In contrast, plant height and leaf carbon content showed no significant changes. Changes in plant height were mainly driven by the covariation between species turnover and ITV, whereas for leaf morphology (leaf area) and leaf chemical traits (leaf carbon, nitrogen, and phosphorus contents), species turnover had a much greater impact than ITV. 3) In the combined warming and nitrogen treatment, community-level leaf phosphorus content decreased significantly by 52.19%, with no significant changes in plant height, leaf area, leaf carbon content, or leaf nitrogen content. The changes in plant height and leaf carbon, nitrogen, and phosphorus contents were primarily driven by species turnover, while leaf area was mainly influenced by ITV. This study suggests that nitrogen addition and warming can alter the functional composition of alpine meadow communities through different mechanisms. Following nitrogen addition, ITV increases functional variability among individuals, enhancing the community’s responsiveness and stability to environmental changes. Under warming treatment, alone or combined with nitrogen addition, species turnover influences the community by altering species composition, directly affecting species diversity and structures, thereby significantly impacting the community function in the alpine meadows of the Tianshan Mountains.

Aims Studying the response of leaf carbon content (LCC) and nitrogen content (LNC), as well as photosynthetic characteristics, to varying levels of nitrogen addition in Leymus secalinus grasslands in northern Shanxi holds significant importance for the sustainable utilization of grasslands in the agro-pastoral ecotone under the backdrop of nitrogen (N) deposition. However, whether the saturation threshold of LCC and LNC to N addition is the same as leaf photosynthetic characteristics and their potential mechanism of the interaction are not clear.

Methods This study focused on the Leymus secalinus grassland in northern Shanxi, across eight N addition levels (0, 1, 2, 4, 8, 16, 24, 32 g·m^-2·a^-1). Morphological characteristics, LCC and LNC, pigment content and the photosynthetic characteristics of Leymus secalinus leaves were measured. N saturation threshold and N response efficiency of LCC and LNC, as well as net photosynthetic rate were also calculated.

Important findings The results showed that: (1) N content per unit leaf mass (LNC_mass) and per unit leaf area (LNC_area) of L. secalinus showed a logistic growth curve with the increase of N addition level. The N saturation response thresholds of LNC_mass and LNC_area were 11.41 and 7.20 g·m^-2·a^-1, respectively. C:N of per unit leaf mass (C:N) and C:N of per unit leaf area (LCC_area:LNC_area) of L. secalinus decreased in power function with the increase of N addition level. (2) Morphological characteristics (leaf length (LL), leaf width (LW), leaf thickness (LT), leaf area (LA)), Pigment content (chlorophyll a content (C_a), chlorophyll b content (C_b), total chlorophyll content (Chl), carotenoids (C_ar)), photosynthetic characteristics (net photosynthetic rate (P_n), transpiration rate (T_r)) of L. secalinus showed the piecewise linear mode of first increasing and then decreasing with the increase of N addition level, and the N saturation response threshold of P_n was 16 g·m^-2·a^-1. However, the stomatal limit value (L_s) and water use efficiency (WUE) changed in the opposite pattern. (3) N response efficiencies of LCC, LNC and P_n (NRE_LCC, NRE_LNC, NRE_Pn) decreased exponentially with the increase of N addition level. (4) Structural equation modeling results showed that P_n was indirectly regulated by LCC and LNC, and the regulation mechanism was different under low N and high N addition treatments. LCC and LNC mediate the regulation of P_n by regulating leaf morphological characteristics at low N addition level; the regulation of P_n was achieved by regulating leaf area and chlorophyll content by LNC at high N addition level. This study showed that LCC and LNC showed nonlinear response, while the photosynthetic characteristics showed linear response characteristics under different levels of N addition. We also explored the regulatory mechanisms of LCC and LNC on photosynthesis.

Aims The impoundment of the Three Gorges Reservoir (TGR) has led to the transformation of a large number of natural riparian zones into reservoir drawdown zones, characterized by reverse seasonal water level fluctuations. This transformation has fundamentally altered the local habitat, significantly impacting the differentiation of plant morphological traits. This study aims to reveal the impact of habitat transformation from “riverbank to drawdown zone” as a result of the TGR backwater disturbance on the functional trait differentiation of adapted herbaceous plants as well as their adaptation strategies.

Methods This study used a typical small watershed (Baijiaxi) in TGR area as a case. Four herbaceous plant species (Cynodon dactylon, Bidens tripartita, Xanthium strumarium, and Polygonum hydropiper) suitable for the local environment were selected as objects. The spatial differentiation characteristics of 17 plant functional trait indicators were analyzed across the habitat transformation from the riparian zone to the drawdown zone. Pearson correlation analysis was employed to explore the co-evolutionary relationships among functional traits, while redundancy analysis (RDA) was conducted to assess the influence of habitat factors on the differentiation of these traits.

Important findings (1) The transition from natural riparian habitats into the drawdown zone resulted in significant variations in the morphological traits of the four plant species. These variations were characterized by increased plant height and decreased root length. These changes were primarily attributed to the restricted growth period imposed by water-level fluctuations and the relatively simplified plant community structure with reduced competitive pressure. Concurrently, leaf thickness increased, and leaf area expanded in most plants, which was mainly driven by intensified drought stress during summer in the drawdown zone. The results highlighted that the backwater effects of the TGR significantly amplified local-scale shape variations among species. (2) The chlorophyll content and net photosynthetic rate of leaves in the four plant species were significantly higher in the drawdown zone compared to those in the natural riparian zone, indicating that plants may have developed an adaptation strategy to enhance photosynthetic efficiency and accelerate growth rates in response to habitat limitations. (3) Under the habitat screening effect of the backwater in the TGR, the four plant species developed a trade-off strategy between “growth” and “drought tolerance”, showing convergent adaptation strategies. Cynodon dactylon exhibited stronger phenotypic variability, especially in photosynthetic traits, suggesting greater adaptability to habitat changes. In contrast, Bidens tripartita, Xanthium strumarium, and Polygonum hydropiper formed more conservative adaptation strategies. (4) RDA showed that variations in functional traits of the four plant species within the upstream riparian zone were primarily associated with soil moisture. While, in the midstream and downstream drawdown zone, these variations were predominantly linked to flooding depth, soil pH and soil temperature, indicating that differences in flooding regimes drove the differentiation of plant functional traits.

Aims This study aimed to reveal variations in ecological stoichiometric characteristics of plant roots and soils in coastal wetlands along a latitudinal gradient, to examine root stoichiometric homeostasis, and to explore the coupling relationships between root stoichiometry and environmental factors.

Methods Plant and soil samples were collected from seven coastal wetlands across China spanning a latitudinal range from 19.87° to 41.03° N. The contents of carbon (C), nitrogen (N), and phosphorus (P) were measured in aboveground plant parts, roots, and soils. The relationships between plant root stoichiometric characteristics and environmental factors were further analyzed.

Important findings Latitudinally driven environmental changes significantly influenced soil nutrient conditions, with soil nutrients in high-latitude coastal wetlands generally lower than those in low-latitude regions. The contents of soil organic carbon (<11.1 g·kg^-1) and total nitrogen (<1.1 g·kg^-1) north of Hangzhou Bay were lower than the national average. The C, N, and P stoichiometric characteristics of plant roots in coastal wetlands were relatively sensitive to latitudinal variation. These variations were closely related to soil nutrient conditions and varied among plant species. The root C content of Spartina alterniflora was extremely significantly positively correlated with soil nutrient conditions. The root C contents of Phragmites australis and × Bolboschoenoplectus mariqueter were significantly negatively correlated with soil nutrient conditions, whereas the root C, N, and P contents and their stoichiometric ratios of Suaeda salsa were significantly positively correlated with soil nutrient conditions. The six plant species also exhibited significant differences in root stoichiometric homeostasis, with the strength of homeostasis decreasing in the order of Avicennia marina, Phragmites australis, Spartina alterniflora, × Bolboschoenoplectus mariqueter, Aegiceras corniculatum, and Suaeda salsa. These results elucidate nutrient dynamics and plant adaptive strategies in plant-soil systems along latitudinal gradients and provide a theoretical basis for vegetation restoration in coastal wetland ecosystems.

Aims Plant functional traits refer to various characteristics of plant morphology, structure, physiology, etc., reflecting plant responses and adaptations to environmental change. Flowers, as the core organs of plant reproduction, possess functional traits that can reflect plant-pollinator interactions, pollinator selection, and carbon investment strategies during the reproductive processes. It has been shown that flowers are developed from leaves, but the differences between flower and leaf functional traits across species remain largely unknown. By systematically quantifying the functional traits of flowers and leaves, this study investigated the differences in structures and functions of these two types of plant organs.

Methods To reveal the differences in functional traits between flowers and leaves, we selected 24 species in South China National Botanical Garden, and measured their both flower and leaf morphological traits (i.e., size and thickness), structural traits (i.e., vein diameter and density, mass per area, and dry mass content), mechanical strength (i.e., force to tear, and force to punch), and physiological traits (i.e., longevity, respiration rate, transpiration rate, stomatal conductance, nitrogen content, and phosphorus content).

Important findings Significant differences were found in the functional traits and carbon investment strategies between flowers and leaves. Force to punch, force to tear, and dry mass content of flowers were 50.0%, 42.9% and 30.7% of leaves. Additionally, the transpiration rate and stomatal conductance of flowers were 73.9% and 84.6% of leaves. Flower size and mechanical strength significantly increased with flower vein diameter, while leaf size was significantly and positively correlated with primary leaf vein diameter. Leaf mechanical strength was significantly and positively correlated with leaf minor vein diameter. Moreover, flower longevity was significantly and negatively correlated with flower respiration rate, transpiration rate, and stomatal conductance, but non-significantly correlated with flower mechanical strength and mass per area. In contrast, leaf longevity was significantly and positively correlated with leaf respiration rate, mechanical strength, and mass per area. Our findings revealed the trade-offs in resource allocation between plant reproduction and growth, and provided data support for species protection in the National Botanical Gardens.