Aims Differences in herbivory among plant species can greatly affect the functioning of forest ecosystems. However, little is known about the main drivers causing interspecific differences in herbivore damage among tree species. The growth-defence trade-off hypothesis posits that intrinsic growth rate of plant species governs resource allocation between defense and growth, thereby shaping interspecific variation in herbivory. However, the validity of this hypothesis is extensively debated, especially in highly species-rich subtropical forests. Methods We quantified leaf herbivore damage in 27 native tree species in a tree species diversity experiment conducted in subtropical China. Concurrently, we measured 12 leaf traits associated with insect palatability and relative growth rates of 27 tree species. Using a combination of phylogenetic multivariate analyses, we assessed trade-offs between leaf traits and the relative effect of these traits on leaf herbivore damage. Important findings We found 1) neither phylogenetic principal component analysis nor hierarchical cluster analysis supported the idea that species displayed one-dimensional trade-off; 2) Conventional strategies, such as condensed tannins, are not strongly involved as a defence against herbivores; 3) No significant trade-off between plant intrinsic growth rate and chemical defence traits for the 27 studied tree species. Our results do not support arguments for growth-defense trade-off hypothesis. Rather, plants display a range of combinations of leaf traits. We suggest this lack of a one-dimensional trade-off may be adaptive, resulting from selective pressure to adopt a different combination of defences to coexisting species.

Aims The trait-based approach has been extensively utilized to evaluate the influence of neighborhood competition on seedling survival. However, previous studies used species average traits, ignoring intraspecific trait variation.

Methods Based on the monitoring of 150 seedling plots in a needleleaf and broadleaf mixed forest in Jiaohe, Jilin, we used a generalized linear mixed effect model of binomial distribution to compare the effects of intraspecific trait variation and species average traits on seedling survival rate, and explore how functional traits mediate seedling responses to neighborhood competition and abiotic environmental factors.

Important findings The intraspecific trait variation model and the species average trait model had inconsistent predictive abilities for seedling survival rate. Specifically, intraspecific variability model of specific leaf area (SLA) exhibited a smaller Akaike information criterion value and Bayesian information criterion value, a larger explanatory variance and a better fit. While species average trait model of leaf area (LA), leaf carbon content (LCC), and leaf nitrogen content (LNC) performed better. In addition, traits mediate the effects of neighborhood competition and soil nutrients on seedling survival. Seedlings with smaller LA have higher survival rates under the same density dependence. Higher LCC increases seedling survival rate in the absence of soil nutrients, while seedling survival rate decreases under fertile soil conditions. The ability of intraspecific trait variation in predicting individual survival of seedlings may not be stronger than species average trait, which may be related to forest stands and environmental factors. In addition, the presence of neighborhood competition and environmental variables can enhance the relationships between traits and seedling survival. Although intraspecific trait variation may not improve the prediction of seedling survival rate, this individual-based approach provides a new perspective for predicting seedling dynamics.

Aims Leaf traits are affected not only by plant sizes, but also by different canopy conditions where mature trees and saplings grow. Thus, these trees choose various survival strategies to adapt to different canopy conditions by adjusting their leaf traits. The aim of this study is to investigate the changes of leaf traits of three Acer trees along with the changes of plant size and canopy condition.

Methods In this study, three species (Acer ukurunduense, A. tegmentosumand A. pictumsubsp. mono) in broadleaf Pinus korainesis forest in Xiao Hinggan Mountains of Northeast China were selected. Six leaf economics spectrum traits, specific leaf area (SLA), leaf dry matter content (LDMC), leaf thickness (LT), chlorophyll (Chl) content, net photosynthetic rate per area (A_area) and non-structural carbohydrates (NSC) content, together with two defensive traits, total phenolics (TP) content and flavonoids (FLA) content of adult trees and saplings in gaps and saplings in understory were measured. Whether leaf traits and their relationships varied with plant sizes and canopy conditions was further analyzed to illustrate how gaps influence forest regeneration by altering leaf traits, and to explore the differentiation of survival strategies for plant individuals growing under various habitats.

Important findings Adults in gaps had higher LDMC, Chl content, FLA content and NSC content compared with saplings in gaps, which meant adults had adequate photosynthetic accumulation and they were more capable to defend against herbivory. LDMC, LT, Chl content and A_area of gap saplings were significantly higher than saplings in understory, indicating that canopy condition was a vital source of leaf trait variations. The absolute slope of relationship between SLA and LDMC for adults was significantly higher than that for saplings in gaps, but the absolute slope of understory saplings was significantly lower than that of the gap saplings. The relationship between defensive traits remained stable among different plant sizes and canopy conditions. These evidences showed that, adults invested more in leaf construction such as leaf thickness and defensive substances, so they chose “conservative” strategy. Saplings in understory improved their ability to acquire light by increasing SLA, they therefore tended to choose “acquisitive” strategy. Saplings in gaps however, showed the transition strategy between “conservative” and “acquisitive” strategies. Results further indicated that, when saplings were not limited by light, their photosynthetic rate increased rapidly to be significantly higher than that of adults. In addition, forest gaps can promote the regeneration of forest stand by enhancing the abilities of photosynthesis and resistance to herbivory of saplings.

Aims Individual size reflects the radial growth of trees, while fine roots are highly sensitive to changes in the rhizosphere soil environment. Investigating the relationship between functional traits of fine root and the microenvironment of rhizosphere soil in trees at different sizes can contribute to elucidating interaction mechanisms within the forest subsurface ecosystem of trees at the individual level.

Methods In this study, fine roots and rhizosphere soil sampling were conducted based on Machilus pauhoi individuals of different sizes in an 11-year-old plantation. The aim is to analyze the relationship between fine root functional traits, rhizosphere soil nutrients content, microbial community structure, and enzyme activities of M. pauhoi individuals of different sizes.

Important findings The results indicate that: 1) There are differences in fine root functional traits and rhizosphere microenvironment among trees of different sizes. Significant differences were observed in traits such as fine root biomass, specific root length, root length density, root volume density, root tissue density, root nitrogen content and root phosphorus content. Except for the specific root area and root tissue density, other fine roots functional traits were highest in the medium-sized individuals, and rhizosphere soil carbon, nitrogen, and phosphorus contents were also highest in medium-sized M. pauhoi. 2) Variability coefficients of fine root traits such as specific root length, root volume density, fine root biomass, and rhizosphere soil fungal and actinomycete contents were relatively large among M. pauhoi individuals of different sizes, particularly pronounced in medium- sized individuals and relatively low in small-sized individuals. All individuals tend to adapt to environmental changes by adjusting traits such as root volume density, fine root biomass, rhizosphere soil fungal contents and nitrate nitrogen content. 3) The fine roots at different individual sizes adopted different resource utilization strategies. Medium-sized M. pauhoi exhibited larger specific root length, root nitrogen content, and root phosphorus content, indicating a resource acquisition strategy to optimize nutrient acquisition capacity. Small-sized individuals with larger root tissue density adopted a resource conservation strategy to enhance their ability to cope with environmental stress, while large individuals exhibited a balanced strategy between above-ground and below-ground growth. 4) Soil total carbon content, microbial biomass carbon content, actinomycete content, ammonium nitrogen content, acid phosphatase activity, and microbial biomass nitrogen content in the rhizosphere soil microenvironment were identified as the main factors influencing fine root functional traits of M. pauhoi. The relationship between fine root functional traits and rhizosphere microenvironment varied among individuals of different sizes. Fine roots of small-sized M. pauhoi individuals were mainly affected by rhizosphere soil nutrients, while those of medium-sized M. pauhoi individuals were primarily influenced by the content of actinomycete and acid phosphatase activity in the rhizosphere soil. Fine root traits of large-sized individuals were affected by both rhizosphere soil nutrients and soil microbial community structure, including bacteria and actinomycete content. The finding provide theoretical insights for implementing afforestation of M. pauhoi on a microtopographic scale, precisely developing artificial forest tending and thinning measures, and cultivating large-diameter timber plantations.

Aims Rhizosphere microorganisms play an important role in plant nutrient acquisition and carbon and nitrogen cycling, and plant fine roots (including absorptive roots and transport roots) are closely related to rhizosphere microbial communities. Elucidating the relationship between changes in fine root traits of pioneer tree species and rhizosphere microbial communities during post-fire forest restoration can provide theoretical support for post-fire vegetation restoration management based on fine roots and rhizosphere microbial dynamics.
Methods The pioneer tree species Betula platyphylla was used as the research object in the 30-year time series of the burned area of Da Hinggan Mountains. The 16S rRNA high-throughput sequencing technology was used to analyze the relationship between rhizosphere bacterial community structure and soil properties and fine root traits of B. platyphylla during post-fire recovery.
Important findings The results showed that post-fire recovery time significantly affected soil pH, absorptive root traits, and rhizosphere bacterial α diversity. With increasing time after fire, soil pH tended to increase, then decrease, and then increase again. The specific root length and specific root area of absorptive roots showed a trend of first increasing and then decreasing. Nine years after the fire was the turning point when the rhizosphere bacterial α diversity of B. platyphylla gradually recovered. Proteobacteria, Actinobacteriota, and Acidobacteriota were the main dominant phyla in the rhizosphere bacterial community at different post-fire recovery times, and Bradyrhizobium was the main dominant genus. Dominant genera such as Roseiarcus, Acidipila and Mycobacterium were significantly different at different post-fire recovery times. The α diversity of rhizosphere bacteria was mainly affected by soil pH and specific root length of absorptive roots, and the change of bacterial community structure was affected by carbon and nitrogen contents of fine roots and phosphorus content of transport roots. In conclusion, the interaction between fine roots, soil, and microorganisms jointly affects the community structure and diversity of B. platyphylla rhizosphere bacteria, thereby shaping the rhizosphere environment and promoting ecosystem recovery after fire.

Aims Grazing is the primary human disturbance in grassland ecosystems and serves as a key external filtering factor in the grassland community assembly. However, the specific mechanisms about the influence of grazing intensity on community assembly in grasslands, particularly the relative roles of intraspecific and interspecific trait variation, remain unclear. This study systematically analyzed the responses of aboveground (shoots and leaves) and belowground (roots) plant traits to grazing, and examined the filtering effect of grazing intensity by considering intraspecific and interspecific trait variation at two spatial scales: from the auger coring to plot scale, and from the plot to site scale.
Methods In this study, we conducted field investigation based on a long-term grazing manipulation experiment in a typical steppe in Nei Mongol, China. Samples of plant aboveground parts and root systems were acquired at the individual plant level using the auger coring method. The filtering effects of grazing intensity were assessed at both the auger coring and plot scales. Furthermore, we explored the regulatory mechanisms of soil moisture and nutrients on grazing filtration.
Important findings (1) Intraspecific and interspecific variations in most aboveground traits tended to increase with higher grazing intensity, they were opposite in root traits. (2) At the auger coring scale, the filtering intensity of grazing based on intraspecific variation and interspecific variation of aboveground traits initially increased, peaked at moderate grazing intensity, and then decreased. However, the filtering intensity based on intraspecific and interspecific variations of root traits consistently increased. At the plot scale, the filtering intensity of grazing based on intraspecific and interspecific variations of aboveground traits linearly decreased; the grazing filtration intensity based on intraspecific variation of roots traits increased, while the grazing filtration intensity based on interspecific differences weakened. (3) As the spatial scale increased, the influence of grazing intensity on grassland community assembly shifted from filtering based on interspecific trait variation to filtering based on intraspecific trait variation. This shift was regulated by soil moisture and nutrient availability. These findings provide new insights into the regulatory mechanisms of grazing on grassland community assembly and provide important bases for understanding vegetation landscape heterogeneity and assessing scale effects resulting from long-term grazing. There were certain limitations in this study, where leaf and root traits mainly focused on structural characteristics. we could integrate chemical traits, such as leaf and root carbon and nitrogen contents, to comprehensively exploring the regulatory mechanisms of grazing on the variation of aboveground and belowground plant traits in future studies.

Aims In the context of global climate change, drought-induced xylem embolism is considered as the main factor driving tree death. Therefore, analyzing the intrinsic anatomical determinants of xylem embolism resistance (water potential at 50% loss of xylem conductivity, P₅₀) is of great significance for understanding the mechanism between its structure and function, and provides a theoretical basis for the selection of tree species for vegetation restoration in the context of climate change.
Methods We measured the xylem vessel diameter, vessel grouping index, fractions of xylem tissues, pit morphology, pit membrane ultrastructure and water storage capacity (such as wood density and saturated water content), and explored the relationships between xylem embolism resistance and their anatomical structure and structural characteristics of 12 main evergreen tree species in Nonggang karst forest of Guangxi.
Important findings We found that: (1) P₅₀ had no significant correlation with vessel diameter, density, vessel grouping index and fraction of xylem tissues; (2) The correlations between P₅₀ and pit morphology, thickness of pit membrane and depth of pit chamber were not significant; (3) P₅₀ was negatively correlated with wood density and marginally positively correlated with saturated water content. Tree species with high wood density and low saturated water content had strong embolism resistance. The results indicated that using a single anatomical structure trait could not give out comprehensive evaluation on drought-induced embolic resistance. In addition, there was a trade-off between xylem water capacity and embolism resistance. This result was of great ecological significance for deeply understanding the internal structural mechanism of drought tolerance and diversified water use strategies of karst plants.

Aims Seed traits are of great significance for clarifying plant population reproduction and renewal strategies. Understanding the response of Artemisia ordosica seed traits to nitrogen deposition and increased precipitation can improve the understanding of desert plant community succession. Methods The study was conducted based on an 8-year field water and nitrogen control experiment (2015-2022). A full factor interaction experiment of ambient precipitation, 20% water increase, 40% water increase and 0, 20, 60 kg N ha?1 yr?1 were carried out to determine the morphological, physiological, chemical and germination traits of A. ordosica seeds. The germination traits of seeds under each treatment at two temperatures (25℃/15℃ and 20℃/10℃) were explored by using the petri dish germination experiment and calculating the germination indexes by observing the number of seedling emergence. Important Findings (1) Nitrogen and water addition, as well as their interactions, significantly influenced the morphological characteristics of A. ordosica seeds, including seed mass, length, width, curvature, volume, form coefficient and other traits. The addition of water resulted in smaller seeds while nitrogen alone led to larger seeds. However, when water was increased by 20%, it mitigated the effect of nitrogen increase on seed size. Conversely, with a 40% increase in water content, nitrogen addition caused smaller seeds. (2) The germination percentage was higher at normal temperature (25℃/15℃) than that at low temperature conditions (20℃/10℃). At low temperature, seed germination traits were more affected by parental water and nitrogen addition, and when only adding 20% and 40% water, the seeds had higher germination percentage. (3) Increase water or nitrogen alone tent to the variation of only one function (dispersal establishment or germination) of A. ordosica seeds, while simultaneous addition of water and nitrogen led to the variation of both functions of A. ordosica seeds. These findings demonstrate that populations of A. ordosica possessed a great adaptability in response to global climate change by altering their functional strategies of seed dispersal establishment and germination under different circumstances through the variation of seed traits.Methods The study was conducted based on an 8-year field water and nitrogen control experiment (2015-2022). Natural precipitation, 20% water increase, 40% water increase and 0, 20, 60 kg N ha?1 yr?1 full factor interaction were used to determine the morphological, physiological, chemical and germination traits of Artemisia ordosica seeds. Two-factor analysis of variance and principal component analysis were used to explore the effects of water and nitrogen addition on seed traits of Artemisia ordosica. Important Findinds (1) Nitrogen and water supplementation, as well as their interactions, significantly influenced the morphological characteristics of Artemisia ordosica seeds, including seed mass, length, width, curvature, volume, shape coefficient, and other traits. The addition of water resulted in smaller seeds while nitrogen alone led to larger seeds. However, when water was increased by 20%, it mitigated the effect of nitrogen increase on seed size. Conversely, with a 40% increase in water content, nitrogen addition caused smaller seeds. (2) The impact of nitrogen addition was more significant than that of water supplementation. The germination rate was higher at normal temperature (25℃/15℃) than that at low temperature conditions (20℃/10℃). However, when only adding 20% water, the seeds had higher germination rate and the highest germination rate occurred under the low temperature condition. (3) Under combined treatments of water and nitrogen supplementation, the shape coefficient, nitrogen content, and various aspects was related to germination such as 2-hour water absorption capacity and overall germination rate jointly regulated the timing function for seed germination. The increase in both water and nitrogen enhanced the ecological coordination strategy employed by Artemisia ordosica seeds. These findings demonstrates that populations of Artemisia ordosica possessed a great adaptability in response to global climate change by altering their functional traits to coordinate ecological functions under different environmental conditions.

Aims Acer pictum subsp. mono is the main accompanying tree species in broadleaf Korean pine (Pinus koraiensis) forests, and plays an important role in the structure and function of broadleaf Korean pine forests. Studying the functional traits of leaves, branches, and roots of Acer pictum subsp. mono at different stages of its life history and their related relationships is of great signifi-cance for understanding the intra species variation of plant functional traits and strategies for re-source acquisition and allocation. Methods This article focuses on the seedling, sapling, and adult tree of Acer pictum subsp. mono in the broadleaf Korean pine forests of Liangshui National Nature Reserve in Heilongjiang. The 12 physiological and morphological traits of leaves, branches, and roots, as well as chemometric char-acteristics such as carbon (C), nitrogen (N), and phosphorus (P) contents, are analyzed, and the in-fluence of different life history stages on the variation of leaf, branch, and root traits and their cor-relation is explored. Important findings (1) With the increase of life history stage, leaf thickness, branch tissue density, root diameter, leaf N content and C contents of leaf branches and roots increased significantly, while specific leaf area, net photosynthetic rate and specific root length decreased significantly, and there was varying degrees intraspecific variation of each trait in life history stage. (2) The correla-tion between physiology-morphological traits and chemical traits was high in leaves and branches, while in fine roots, only specific root length is correlated with chemical traits. (3) With the increase of life history stages, the N content and net photosynthetic rate of the leaves increase, and the ac-cumulation of photosynthetic products is more. The leaves change from a “slow investment return” type to a “fast investment return” type. The metabolic capacity such as branch water content and the resource acquisition ability of fine roots decrease, and both branches and roots transition from a “resource acquisition” type to a “resource conservation” type.

Aims Clarifying the network characteristics of plant traits is one of the research hotspots in functional ecology. However, the understanding of plant trait networks and their driving factors at the seasonal scale is still limited. Methods We used a Li-6400 portable photosynthetic instrument to regularly measured the light response and carbon dioxide response curves of Artemisia ordosica during the growing season (May-September), and leaf structural and biochemical indicators as well, to explore the correlation and trait network characteristics among 25 leaf traits. Important findings There are significant correlation between leaf traits at the seasonal scale, and the closest coupling relationship between traits occurs between photosynthetic physiological traits, with a total of 67 pairs of physiological trait combinations showing significant correlation. The edge density, diameter, average path length, and modularity of the plant trait network (PTN) are 0.58, 3, 1.51, and 0.08, respectively. The betweenness of leaf tissue density (LTD), leaf nitrogen content per unit area (Narea), and transpiration rate (E) is relatively high, making it a "bridge" in PTN. PTN does not have an absolute central trait, and physiological traits as a whole exhibit high degree, eigenvector centrality, and clustering coefficient, indicating that the trait network is jointly dominated by physiological traits. Further analysis indicates that the 25 leaf traits at the seasonal scale can be compressed into two major trait dimensions: one is regulated by air temperature and soil moisture, and the other is regulated by photosynthetic effective radiation. The research results emphasize that when evaluating the potential response of different trait functional groups to climate fluctuations, it is necessary to distinguish the degree and effect of environmental factors on different traits. If the seasonal response of plant traits to the environment is included in a unified paradigm, it will wrongly evaluate the adaptability of plant traits.

Aims Artificial vegetation, human planted and being that managed and influenced by human activities, is widely distributed all over the world, and its structure, process, pattern, and function are important topics in modern ecology. However, there are few studies on plant functional traits of artificial vegetation, which limit the understanding of artificial vegetation, especially agricultural vegetation. The aims of this study are to investigate key features of plant functional traits in main artificial vegetation types of Jinhua, Zhejiang, and to explore potential ways they have adapted to human disturbance.

Methods Above- and below-ground plant functional traits (leaf, twig or stem, and fine root) of eight dominant species in seven common artificial vegetation types in Jinhua, Zhejiang, were measured. Key characteristics of plant traits such as mean value, variability, correlation, and plant growth trade-offs were statistically analyzed. Combinations of above- and below-ground traits of different planted species were further analyzed by the principal component analysis to identify ecological strategies of these common planted species.

Important findings (1) Plant functional traits, and variation in artificial vegetation, exhibited different features. Woody plants had higher dry material content and tissue density in leaf, twig and fine root tissues, indicating stronger material storage capacity, whereas herbaceous plants had higher specific leaf area, specific root length and specific root area, facilitating quick access to resources. The ranges in the coefficient of variation (CV) of functional traits in woody, and then herbaceous plants were 8.80%-40.94% and 37.05%-61.60%, respectively. Furthermore, the CV for woody plants was generally smaller than that of herbaceous plants, indicating the latter were more sensitive to habitat changes. Species composition and the interaction between habitat and management, were the major factors affecting artificial vegetation traits. (2) Plant functional traits of different organs showed mostly positive and significant correlations, reflecting the synergy of artificial vegetation plant traits. (3) Different combinations of functional traits of species in different artificial vegetation types reflected various adaptation strategies. The leaf and fine root traits of peach (Amygdalus persica), with a larger specific leaf area, larger twig bark thickness, and smaller fine root diameter, showed the ability of quickly acquire resources, while camellia (Camellia japonica) tended to have greater leaf thickness, increased leaf mass per area and a coarser fine root component. This reflects a stronger substance accumulation and defense capacity. The orange (Citrus reticulata) however had intermediate trait values. The tea plant (Camellia sinensis) had flourishing fine roots to acquire more nutrients. Rice (Oryza sativa) and rape (Brassica napus) had stronger abilities to accumulate substance and to absorb nutrients because of their larger leaf thickness, greater specific leaf mass per area, and lower stem and fine root tissue densities. However the trait combinations of two artificial grassland species, Bermuda grass (Cynodon dactylon) and bluegrass (Poa annua) were in contrast with the above two crops. The study of plant functional traits, their trade-offs, and the various combinations of artificial vegetation from an ecological perspective, provide a scientific basis and new ideas for the management of anthropogenic ecosystems.

Aims Functional traits can individually or jointly reflect the response of plants to environmental changes and their adaptation strategies and are closely linked to ecosystem functioning. Exploring the functional traits and trait space characteristics of wetland plants is of importance for understanding the mechanisms underlying the ecological adaptability of wetland plants in river floodplains.

Methods We measured 10 functional traits of 30 common herbaceous plants in 5 river floodplains around Wuhan in middle reaches of Yangtze River. We then analyzed the relationships among traits, the quality of trait space, the importance of traits, and the distribution of species in trait space.

Important findings The results showed that variations in functional traits were large among wetland plant species and that trait-trait relationships were generally weak. The quality of trait space increased rapidly when the dimension of space increased from one to four, with the six-dimensional space being of the highest quality. Considering a tradeoff between dimension reduction and space quality, we chose the four-dimensional space for subsequent analyses. In the four-dimensional space, life span, rhizome, plant height, leaf area, specific leaf area, leaf dry matter content, leaf nitrogen content and leaf carbon content were significantly correlated with the axes of the trait space, indicating that they played an important role in shaping the trait space of wetland plants. Sixteen species were located at the vertices of the convex hull, of which ten had high frequencies of occurrence, indicating that these species hold unique trait values and might be more important in shaping the trait space than other species.

Aims Fine roots are important organs for absorbing and transporting nutrients during plant growth and development. Investigating the variation and trade-offs among functional traits of seedling fine roots of different mycorrhizal types is conducive to a more comprehensive understanding of their early survival strategies.

Methods In this study, we analyzed the variation and trade-offs across different mycorrhizal types, root orders and root functional modules. In particular, we measured three morphological traits (specific root length (SRL), root tissue density (RTD), and root diameter (D)), and four chemical traits (total phosphorus (P) content, total carbon (C) content, total nitrogen (N) content, carbon nitrogen ratio (C:N)), in three arbuscular mycorrhiza (AM) and three ectomycorrhiza (EM) tree species seedlings in mixed broadleaf-Korean pine (Pinus koraiensis) forest in the Liangshui National Nature Reserve, Heilongjiang Province.

Important findings The results showed that EM seedling fine roots exhibited higher RTD compared with AM seedlings, potentially due to the colonization patterns of AM fungi which increased root volumes and increased the absorptive capacity of limiting nutrients. Other traits did not differ significantly between the two types of mycorrhiza, with AM seedling roots aligning with a more resource-acquired strategy, in contrast to EM seedlings. As the root order increased, RTD and D of both mycorrhiza-association seedling roots increased significantly, while SRL decreased, indicating a functional shift from absorption to transportation. Concurrently, C content and C:N of roots increased, while the N content of roots decreased with increasing root order. A notable trade-off was observed between morphological and chemical traits of fine roots, suggesting that changes in root functional modules with root order are accompanied by corresponding shifts in root traits. These findings support the root economics spectrum (RES), highlighting the complex interplay between root morphology, chemistry and ecological strategy.

Aims Patterns of leaf trait variation and correlation have long been a key aspect in unraveling plant responses to climate change. However, the specifics of how these patterns of leaf structural traits and photosynthetic physiological characteristics align and differ across growth types of broadleaf plants remain unclear.

Methods This study focused on 18 dominant or common broadleaf species in a mixed broadleaf-Korean pine (Pinus koraiensis) forest. We measured four structural traits (leaf area (LA), leaf thickness (LT), leaf dry matter content (LDMC) and leaf mass per area (LMA)) and four photosynthetic physiological traits (leaf chlorophyll value (SPAD), intercellular CO₂ concentration (C_i), stomatal conductance (G_s) and net photosynthetic rate (P_n)). We analyzed the variation and correlations between structural and physiological traits across different growth types of broadleaf plants.

Important findings Leaf functional traits displayed variation ranges spanning from 7.73% to 74.54%. Interspecific differences accounted for the majority of variability for LA and LT, while growth type primarily drove variation in C_i, SPAD, LDMC, and LMA. G_s and P_n variation originate mainly from intraspecific differences. There were significant differences among growth types for all leaf traits. Specifically, herbs showed significantly higher LA, LT, and C_i compared to shrubs and trees, trees exhibited significantly elevated LMA, LDMC, SPAD, P_n, and G_s compared to shrubs and herbs. There were significant isometric relationships between P_n and LMA, LDMC among growth types, with slopes above 1. For SPAD versus LA, LT, LDMC, LMA, along with C_i versus LT, LDMC, LMA, slopes remained under 1, indicating allometric growth relationships. Herbs displayed a resource-acquisitive strategy, while trees adopted a relatively conservative strategy. Falling intermediate, shrubs struck a balance, possibly linked to the light levels across their habitats. Investigating trade-off and connections between leaf structure and photosynthetic physiology proves critical for understanding resource acquisition and allocation mechanism in plants.

Plant functional traits are generally defined as relatively stable and measurable morphological, physiological, and phenological characteristics of plants that can indirectly affect plant growth, reproduction, and survival. Years of development have enabled the standardization of the definition, connotation, and measurement methods of plant functional traits. Now, the intraspecific and interspecific variation, biogeographic patterns, coordination, and the evolution of plant functional traits have been well explored. The gradual development of global plant functional trait databases since the 1990s has led to the expansion of plant functional traits beyond individual and local scales. Regional and global biogeographical studies on plant functional traits are gradually exploring community species coexistence mechanisms and maintenance of ecosystem functions. Researchers have found that traditional plant trait databases, which were created from published studies, have insufficient data to provide answers to questions about natural ecosystems. Therefore, constructing a plant trait database that considers compatibility and orderliness is crucial. As new databases and scientific concepts have emerged, the following areas have become the focus of studies on plant functional traits: 1) coordination between functional traits of different plant organs, and holistic examination of plant response to environmental changes; 2) multi-dimensional response and adaptation of various plant functional traits, and proposal of the concept of a plant trait network; 3) consideration of the complexity of plant community structure, and exploration of community assembly using plant functional diversity and trait moments; and 4) refinement of the scaling method for different levels of ecological organization, and recognition of plant community and ecosystem traits as critical bridges between plant traits and macroecology. These directions have pushed for the application of traditional functional trait research to natural, social, and economic systems, thus promoting the rapid development of trait-based studies to further solve regional eco-environmental problems.

Aims As an important organ for plant nutrient acquisition and energy transport, fine roots are the most active and sensitive part of the root system. Their functional traits change along the environmental gradient, which can reflect plant resource acquisition strategies and adaptability to environmental changes. The purpose of this study was to analyze the effects of different nitrogen (N) addition levels on the morphological and chemical traits of the fine roots of Castanopsis hystrix, explore the plasticity of the fine roots of the species to short-term N addition, and provide theoretical support for clarifying and predicting the changes of root physiological function under global climate change.

Methods In January 2020, four treatments with different N addition levels were set up in the C. hystrix plantation, which were the control (CK, 0 kg·hm^-2·a^-1), low N treatment (LN, 50 kg·hm^-2·a^-1), medium N treatment (MN, 100 kg·hm^-2·a^-1) and high N treatment (HN, 150 kg·hm^-2·a^-1), with three replicates per treatment. Fine roots of C. hystrix were dug out by the excavation method, and traits of the 1st to 5th order fine roots in different N addition treatments were determined, including specific root length, specific root area, root tissue density, average root diameter and stoichiometry.

Important findings The results showed that, compared with the CK treatment, MN and HN treatments significantly reduced soil pH, HN treatment significantly increased soil NO₃^--N and total phosphorus contents. Nitrogen addition significantly increased the content of carbon (C) in the 1st order fine root. HN treatment significantly increased the C content of the 2nd order fine root. MN and HN treatments significantly increased the N content of the 1st and 2nd order fine root, and significantly decreased the C:N of the 2nd order fine root. There were no significant differences in specific root length, specific root surface area, root tissue density and average root diameter of fine roots under different N addition levels. Taken together, these results showed that short-term N addition mainly affected the element content and stoichiometric ratio of fine roots, but had no significant effect on the morphological traits of fine roots in the C. hystrix plantation. This finding will help to understand the response of forest nutrient cycling and C sequestration to global environmental changes in the southern subtropical region.

Aims Nitrogen (N) is an important nutrient element affecting plant growth, biomass allocation and functional trait strategies. Revealing the ecological responses of different provenances to N deposition can help elucidate the adaptation mechanisms of plant species.
Methods In this study, Machilus pauhoi seedlings from 6 provenances in Wanmulin, Fujian Province (WML), Mangdang Mountain, Fujian Province (MDS), Suichuan, Jiangxi Province (SC), Jiande, Zhejiang Province (JD), Chaling, Hunan Province (CL) and Anfu, Jiangxi Province (AF) were selected as our study objects. By setting two treatments of fertilization and no fertilization, we investigated the effects of N addition, provenance and their interactions on biomass allocation and functional traits of M. pauhoi seedlings.
Important findings 1) Nitrogen addition significantly promoted total biomass accumulation and the relative growth rate of M. pauhoi seedlings, with the greatest response observed for JD seedlings. However, the effect of N addition on biomass allocation varied by provenance, with JD and AF seeding showing increased leaf mass fraction, and WML and AF seedlings showing increased leaf stem ratio. 2) The effects of N addition on leaf traits of seedlings also varied by provenance. N application significantly reduced the specific leaf area of JD, CL and AF seedlings, but increased the leaf area and leaf N:phosphorus (P) of CL seedling. 3) The response of major functional traits of fine roots to N addition also varied by provenance. N addition significantly decreased the average root diameter and root tissue density of SC, JD and AF seedlings, but increased the root tissue density of WML seedling, the specific root length of MDS and JD seedlings, and the specific surface area of SC and JD seedlings. N addition significantly increased the fine root N content of AF seedling, but decreased the fine root P content of WML, MDS and SC seedlings, and the fine root N:P of all provenances were significantly higher in fertilization treatments than in the control. 4) We observed higher phenotypic plasticity in fine root and biomass-related phenotypes than in leaf traits among different provenances, with the highest phenotypic plasticity in the JD seedling and the lowest phenotypic plasticity in the SC seedling. 5) Structural equation modeling showed that N addition and provenance had significant effects on the growth of M. pauhoi seedlings, with N addition influencing growth by affecting leaf stem ratio and leaf N:P, and provenance influencing growth by affecting specific leaf area and fine root surface area. The growth, biomass and functional traits of M. pauhoi seedlings from different provenances have different ecological adaptation strategies to N addition. Among them, JD seedlings is more adaptable to changes in the external environment, which may account for its long-term adaptation to the provenance environment. Our results provide a theoretical basis for the selection of optimal provenance of M. pauhoi in subtropical regions of China that affected by N deposition.

Aims The xylem water transport resistance and leaf transpiration rate of tall trees increased with tree height, resulting in a water supply-demand paradox along the tree height gradient. Quantitative analysis of the variation and coordination of related functional traits along tree height will be conducive to deeply understanding the water supply and demand mechanism of plants.

Methods Here, Taxodium distichum and its variety T. distichumvar. imbricatum grown in a mesic common garden were studied, with hydraulic (sapwood-specific hydraulic conductivity (K_s), leaf specific conductivity (K_l), the water potential causing 50% loss of conductivity (P₅₀), maximum transpiration rate (T_r), midday leaf water potential (ψ_MD), Huber value (H_v), etc.), photosynthetic (maximum photosynthetic rate (P_n)) and carbon economic traits (leaf mass per unit area (LMA), wood density (WD)) measured. Traits variation and coordination along the tree height and traits differences between the same canopy of T. distichum and T. distichumvar. imbricatum were analyzed by a series of methods, including regression analysis, one-way ANOVA, and path analysis.

Important findings We found that: (1) K_l, H_v, P_n and LMA in T. distichum and T. distichumvar. imbricatum increased along the height, and the increase of P_n may be related to the decrease of T_r and maximum operational stomatal conductance (G_s) in the middle canopy. (2) Coordination relationships between intraspecific traits: K_s in T. distichum and T. distichumvar. imbricatum was significantly negatively related to H_v, WD in T. distichum was significantly positively related to K_s, and WD in T. distichumvar. imbricatum was significantly negatively related to H_v. (3) There was water limitation in the higher canopy of T. distichum and T. distichumvar. imbricatum. The theoretical water supply and demand ratio (r) calculated by Darcy’s Law and T_r confirmed this limitation. The theoretical maximum height when r = 0: T. distichum 32 m (upper bound of 95% confidence interval: 57 m); T. distichumvar. imbricatum 21 m (upper bound of 95% confidence interval: 27 m), was consistent with the maximum height recorded historically. (4) K_l, H_v and LMA in canopies of T. distichumvar. imbricatum were significantly higher than those of T. distichum,while P_n, T_r and G_s were significantly lower; hydraulic safety margin (HSM) in the middle and higher canopies of T. distichumvar. imbricatum was significantly higher, and P₅₀was significantly lower: The conservative hydraulic strategy of T. distichumvar. imbricatum corresponded to lower resource acquisition capacity, which in turn resulted in lower maximum growth height. The radical hydraulic strategy of T. distichum corresponded to higher resource acquisition capacity, which in turn resulted in higher maximum growth height.

Aims Trait-based methods have provided a new viewpoint for predicting community dynamics. We use these approaches to reveal how functional traits influence the key demographic rates of plant species, thereby improving our understanding of community dynamics.

Methods We monitored the growth and mortality rates of 26 common woody plant species from Dajinshan Island, Shanghai, over a five-year period (2016-2021). Nine leaf and wood traits related to competition and utilization strategies for light, water and nutrient resources were measured. Then, the relationships between the relative growth and mortality rates and each of individual trait, as well as the multi-trait synthesized plant economics spectrum, were analyzed.

Important findings Our results showed that leaf area and leaf nitrogen content were significantly and positively correlated with the relative growth rate, while leaf thickness, twig wood density and leaf dry matter content were significantly and negatively correlated with the relative growth rate. Stem wood density and twig wood density were significantly negatively correlated with the relative mortality rate. The plant economics spectrum that is formulated by nine traits, could explain 32.8% variation in relative growth rate; however, it did not correlate with the relative mortality rate. The relative growth was higher for acquisitive species than that for conservative species. Our results suggest that plant functional traits are important in affecting their growth, and that plant economics spectrum can accurately predict variations in relative growth rates among species, but its predictions for relative mortality are weaker.

Aims This study aims to clarify the differences in ecological strategies between karst and non-karst forest tree species, in terms of leaf morphology and anatomy, hydraulics, and mechanical resistance.

Methods A total of 101 tree species were selected from typical karst and non-karst forests in tropical-subtropical regions. We measured: (1) leaf morphological and anatomical traits including leaf thickness (LT), leaf density (LD), vein density and leaf mass per area (LMA); (2) leaf mechanical traits including force to punch and force to tear (F_t); and (3) leaf hydraulic traits including maximum hydraulic conductance (K_{leaf_max}), cavitation resistance (P50_leaf), turgor loss point (Ψ_tlp), and stomatal safety margin (HSM_tlp). We compared the differences in leaf traits between karst and non-karst forest tree species, and analyzed their traits correlation networks.

Important findings (1) Compared to non-karst forest tree species, on average the karst tree species had greater F_t, higher K_{leaf_max}, lower (more negative) Ψ_tlp and HSM_tlp. (2) Leaf trait network of karst forest tree species showed shorter average path length and diameter and lower edge density than non-karst forest tree species, indicating that traits combinations were closer in karst forests. (3) Mechanical traits and LMA showed high connectedness in the trait networks of karst forest tree species, LT and LD showed high connectedness in those of non-karst tree species. In karst forest tree species, LMA was positively correlated with F_t and negatively correlated with Ψ_tlp, indicating that increasing leaf carbon investment can simultaneously enhance meachnical resistance and drought tolerance. However, no such correlations were found in non-karst forest tree species. (4) Across karst forests tree species, we found a significant tradeoff between K_{leaf_max} and P50_leaf, both of which were not related with leaf mechanical resistance, and morphological and anatomical traits. By contrast, there was no hydraulic tradeoff in non-karst forest tree species, and K_{leaf_max} was significantly correlated with LT and LD. This study further reveals that compared to non-karst forest tree species, karst forest tree species tend to exhibit isohydraulic strategy and show closer coordination among leaf traits.

Aims Haloxylon ammodendron is the major dominated species in the Gurbantünggüt Desert, which plays a key role in ecosystem services: such as biodiversity conservation and prevention of dryland degradation. Frequent droughts have a significant impact on the survival of H. ammodendron, thus understanding the drought resistant strategies of H. ammodendron is essential for the sustainability and stability of desert ecosystems. Robust hydraulic system and carbon balance are important parts of the drought resistance mechanism, but the hydraulic threshold for survival of H. ammodendron under drought stress are still unquantified.

Methods We set up a control group and a drought treatment group for adult H. ammodendron, and determined the water status of assimilation twigs, the loss rate of xylem hydraulic conductivity in branches, gas exchange characteristics, nonstructural carbohydrate (NSC) contents and morphological characteristics at upper, lower and middle branches of H. ammodendron. We used one-way ANOVA for each trait among different treatments and heights, linear regression for stomatal sensitivity and principal component analysis for drought resistance of H. ammodendron, respectively.

Important findings (1) The predawn and midday water potential of assimilation twig, assimilation twig water content and branch water content of H. ammodendron decreased under drought stress, but did not affected by the increase of height; P50 and P88 (xylem tension causing 50% and 88% loss of maximum hydraulic conductivity) did not change significantly under drought and with increasing height, and the mean value of P50 was -4.12 MPa and P88 was -7.10 MPa for each height and treatment groups, while the hydraulic safety margin was significantly reduced under drought. (2) The stomatal opening of H. ammodendron was not sensitive to drought stress, and thus drought stress and branch height increase did not significantly affect net photosynthetic rate and stomatal conductance in general. (3) The NSC contents of assimilation twigs and branches did not decrease under drought stress or with increasing branch height; the value of NSC contents in the assimilation twigs and branches were 22.11% and 13.10% higher, compared to the control group. (4) The Huber value of H. ammodendron increased by 73.78% in the drought treatment group compared to the control group; the specific leaf area decreased by 14.60% compared to the control group, but there were no significant difference between the two treatment groups. In conclusion, the hydraulic traits of H. ammodendron were significantly affected by drought stress, but not by the increase of branch height, and there was no hydraulic limitation with increasing branch height. Under drought stress, the risk of simultaneous hydraulic failure of the peripheral branches at the crown edge was high, the hydraulic safety margin (difference between midday assimilation twig water potential and P88) was only 40.85% of that of the control group. Due to the low sensitivity of stomata to water stress, the shrub can maintain the capacity of photosynthetic carbon fixation under drought stress, and even slightly increased NSC contents of the assimilation twigs and branches.

Aims Comparing functional traits of coexisting tree species in natural forests can reveal the adaptation strategies of different tree species to different habitats, which is essential for understanding the coexistence mechanism of the local forest community and guiding forest restoration.
Methods In this study, we compared the functional traits of five coexisting tree species in a Quercus aliena var. acuteserrata forest, the zonal vegetation in the Qinling Mountains, and further examined the difference in the traits space defined by the first two principal component analysis (PCA) axes to reveal the differences of these tree species in ecological strategies.
Important findings The results showed that there were obvious differences in the above- and belowground functional traits of different tree species, especially in the strategies of leaf resource acquisition and defense. Specifically, Acer davidii tended to have more acquisitive leaf traits and fine root traits, while Carpinus cordata was relatively more conservative in leaf and fine root traits. Lindera obtusiloba was inclined to have leaves with high resistance and defense ability, while leaves of Cornus kousa subsp. chinensis showed low resistance and defense ability. The dominant species, Q. aliena var. acuteserrata, occupied the middle position along the strategy gradient. The differences in the functional traits and their combinations of coexisting tree species in Q. aliena var. acuteserrata forest reflect their differences in ecological strategies and niches, which may contribute to their stable coexistence.

Trade-offs among plant functional traits reflect the trade-off relationships between resource acquisition and conservation of different plants, which are of pivotal importance for understanding the mechanisms by which plants adapt to the environment. However, due to the heterogeneity of the soil environment and the limitations of technical means, the study of below-ground root functional traits and their interrelationships is currently lagging behind that of above-ground functional traits. Traditionally, fine roots have been defined as all roots ≤2 mm in diameter. The acquisition and utilization of soil resources by plants depends on architectural traits, morphological traits, chemical traits and biotic traits of fine roots and so on, including fine roots associations with mycorrhizal fungi. Recently, the root economics space has been proposed, which demonstrates the existence of trade-offs between the do-it-yourself strategy of plants increasing their own root surface area and the outsourcing strategy of investments into fungal symbionts for enhanced nutrient mobilization from hyphal expansion, in addition to the traditional trade-offs between fast (high nitrogen content and metabolic rate) and slow (high tissue density) investment return. It was found that thin-root species obtained soil resources mainly by increasing specific root length, whereas thick-root species relied more on mycorrhizal fungi. However, the carbon economy of resource acquisition through the root and mycorrhizal hyphal pathways remains unclear. In future research, the key issues of root functional traits were suggested as follows: 1) for research methods, it is urgent to establish a unified set of definitions and research methods for root classification, sampling, storage, functional traits and their research methods; 2) for research traits, the research of “hard” traits of fine roots should be strengthened; 3) for the trade-offs between functional traits of fine roots, it is of great significance to strengthen the study of the trade-offs between construction costs and resource benefits between plant roots and mycorrhizal fungi.

Aims Understanding the differences in leaf functional traits and their correlations in ferns at different vertical heights can provide a scientific basis for revealing the resource utilization strategies of large fern fronds.

Methods Individuals of three fern species in a mixed broadleaved-Korean pine (Pinus koraiensis) forest, i.e., Dryopteris crassirhizoma, Athyrium brevifrons and Matteuccia struthiopteris were divided into upper, middle, and lower layers according to the vertical height of leaves. We measured specific leaf area, leaf dry matter content, net photosynthetic rate, instantaneous water use efficiency, leaf nitrogen content and leaf phosphorus content, as well as the light environment and soil factors of each individual plant to reveal the vertical variation patterns and correlations of leaf functional traits.

Important findings (1) Leaf dry matter content of the three fern species increased with the vertical height of the fronds, but specific leaf area showed no variation. The net photosynthetic rate of A. brevifrons and M. struthiopteris showed an increasing trend with the increases of vertical height of fronds, the instantaneous water use efficiency of M. struthiopteris increased and then decreased with the vertical height of the fronds, and leaf nitrogen content gradually decreased; leaf phosphorus content of D. crassirhizoma showed an increase and then decreased trend. (2) There were positive correlations between leaf nitrogen content and specific leaf area, and also between instantaneous water use efficiency and net photosynthetic rate. There were negative correlations between leaf nitrogen content and leaf dry matter content, and between leaf dry matter content and specific leaf area. The correlations among those leaf functional traits did not differ significantly among different vertical heights. (3) Soil available phosphorus content and soil pH were the main factors affecting the variation of leaf functional traits at different vertical heights, with soil available phosphorus content having the highest explanatory degree to the variation of leaf functional traits. Our results indicated that there were vertical differences in leaf functional traits of large ferns in the mixed broadleaved-Korean pine forest, but the rate of change among individual characters was basically constant, the effects of light environment and soil factors on the variation of leaf functional traits differed among vertical heights. This study provided reference for further research on the mechanism of leaf functional traits variation in different vertical heights of ferns in understory.

Aims Leaf is an important organ for forest trees to acquire and utilize survival resources, and its morphological structure reflects the habitat adaptability of trees to a certain extent. Exploring the role of geography and climate of the Nanpan-Hongshui River basin in shaping the needles morphology and microstructure of an important tree species in the region, Pinus yunnanensis var. tenuifolia, has important reference value for understanding the ecological adaptability and resource conservation of this tree species.

Methods Eighteen morphological and microscopic characters of nine wild populations which distributed in Guizhou and Guangxi were measured, and seven geographical and climatic factors of the nine population locations were recorded. The population divergence and environmental associations were analyzed by nested ANOVA, correlation analysis, multivariate statistical analysis (principal component analysis, redundancy analysis, and hierarchical clustering analysis).

Important findings The results showed that, except for the ratio of needle cross-sectional area to central cylinder area (V1), all indicators had different degrees of differentiation among populations (phenotypic differentiation coefficient (V_ST) = 22.32%-51.42%). It implied that the habitat heterogeneity among populations had a significant impact on most indicators. Pearson correlation analysis and multivariate statistical analysis showed that the indicators which related to needle resin canals (resin canals number, resin canals perimeter, resin canals area, etc.) increased with the increase of latitude, altitude, and mean annual precipitation, but decreased with the increase of mean annual temperature; the stomatal indicators (stomatal density, ratio of stomatal density to V1) increased with increasing latitude and longitude, and decreased with increasing relative humidity; the indicators which related to the needle cross-sectional size (needle width, needle thickness, needle cross-sectional area, central cylinder area, etc.) are mainly affected by the distance from the sampling site to the Nanpan-Hongshui River. The closer the distance, the smaller the indicator value is. To sum up, P. yunnanensis var. tenuifolia exhibits a trend of miniaturization of resin canal, which was driven by dry-hot habitat selection that is different from that of the original species Pinus yunnanensis. Its higher stomatal density (and sunken stomata) is conducive to balancing respiration and transpiration dehydration in arid environments. The relatively slender needles may be mainly shaped by the stress effects of foehn and strong canyon winds which caused by the special valley terrain in the region, as well as the growth limiting effects of seasonal warm and dry climate on needles.

Aims The aims are to understand the change rule and response mechanism of Leymus chinensis under the disturbance and to provide a theoretical basis and reference for the research on the response of plant functional traits to environmental changes under interference and the restoration of plant population in natural grassland.

Methods We investigated the impacts of fertilization on functional traits of leaves, stems and the whole plant of L. chinensis in the vegetative phase in a meadow in Hulun Buir. Firstly, a ground intrusive root-cutting machine (9QP-830) was used to cut the roots of the grassland, and then different levels of nitrogen and phosphorus mixed fertilizers were applied. Finally, multiple functional traits including single plant height, leaf length, natural leaf width, unfolded leaf width, stem width, stem length, leaf mass, stem mass and single plant mass were measured by stages during the vegetative growth period of L. chinensis. The dynamic changes of functional traits before and after fertilization were analyzed.

Important findings (1) Fertilization significantly increased the aboveground biomass of L. chinensis in the later vegetative growth stage, increased plant height, leaf length, natural leaf width, unfolded leaf width, leaf area, stem length, stem width and stem mass, and decreased leaf dry matter content and stem dry matter content. (2) Fertilization significantly modified the changing trend of functional traits of L. chinensis during the nutritional period. With the increase of fertilization level, plant height, leaf length, natural leaf width, unfolded leaf width, leaf area, specific leaf area, stem length, stem width and stem mass increased gradually from the first increase and then decrease trend of change into a gradual increase, while leaf dry matter content and stem dry matter content decreased gradually. (3) There was a close relationship between phenotypic traits and mass traits of L. chinensis. Leaf area was positively correlated with aboveground biomass and stem dry matter content, and negatively correlated with leaf dry matter content. (4) Fertilization changed the contribution rate of phenotypic traits to aboveground biomass during vegetative growth period of L. chinensis. After fertilization, the phenotypic weight of L. chinensis changed from “concentration-dispersion-concentration-dispersion-concentration” to “dispersion-concentration-dispersion-concentration-dispersion”. In the process of vegetative growth of L. chinensis, plant height is the most sensitive trait to fertilization, and it is also the main phenotypic driving factor affecting the aboveground biomass.

Aims Leaf temperature is one of the important microenvironmental parameters for energy exchange and physiological processes of plants. Leaf thermal traits can regulate leaf temperature so as to relieve heat damage to some extent. However, systematic studies on leaf thermal traits are rare.
Methods In the present study, 43 dominant canopy species of four typical vegetation types with varying temperature and precipitation from tropical to temperate zones in Yunnan Province were selected: savanna vegetation, tropical rain forest, subtropical evergreen broadleaf forest, and temperate mixed forest. We selected 23 thermal traits that might have influence on leaf temperature, including leaf morphological, optical, material property, anatomical and physiological traits.
Important findings The results showed that plants in savanna vegetation mainly relied on transpiration for cooling. Savanna species have thin leaves and short life span. They are mainly “quick investment-return” species. Tropical rain forest plants developed large leaves, with low transpiration rates, which have no advantage of leaf cooling. Thick leaves and high water content can alleviate high temperature to some extent. They adopted “slow investment-return” strategy. Subtropical evergreen broadleaf forest was rarely exposed to extreme temperatures. The species had thick leaves, long leaf life span, and adopted “slow investment-return” strategy. They did not show obvious thermal adaptation traits. Temperate mixed forest had small and thick leaves, growing in clusters which provides benefits for thermal insulation. Photosynthetic rate of canopy evergreen plants in this forest was low, adopting “slow investment-return” strategy, while photosynthetic rate of deciduous plants was high, presenting “quick investment-return” characteristics. This study systematically investigated the variation of leaf thermal traits and plant adaptation strategies along temperature and precipitation gradients, providing a theoretical basis for further understanding of plant adaptation to the environment.

Aims Exploring intraspecific variations of plant functional traits with abandoned years and the relevant driving factors will deepen our understanding about the vegetation recovery of abandoned lands and thus guide our agricultural management.

Methods Using the method of substitution of space for time, we set up 42 plots in four types of habitat, i.e., field margin, abandoned grassland, shrub-grassland and forest which represents community succession along a chronosequence of vegetation restoration in Sitang town, Lingui District of Guilin in the middle reaches of Lijiang River watershed. We investigated change of intraspecific variation of five functional traits (i.e., leaf mass per area, leaf dry matter content, leaf nitrogen (N) content, leaf phosphorus (P) content and plant height) for four common herbaceous species (Imperata cylindrica, Paspalum distichum, Bidens pilosa and Alternanthera philoxeroides) with abandoned years. We also investigated the effects of soil properties and woody plant coverage on the intraspecific variation of functional traits.

Important findings With the increase of abandoned years, soil N and P content decreased significantly, soil N:P increased first and then decreased, and the woody plant coverage increased significantly. Leaf N content of I. cylindrica increased significantly, while leaf P content decreased significantly with the increase of abandoned years. This is because leaf N content decreased significantly and leaf P content increased significantly with the increase of soil P content. Leaf mass per area and leaf dry matter content of P. distichum increased significantly and plant height decreased significantly with the increase of abandoned years. Plant height of B. pilosa decreased significantly with the increase of abandoned years, because plant height of B. pilosa decreased significantly with the increase of woody plant coverage. Leaf mass per area of A. philoxeroides decreased significantly with the increase of abandoned years, because leaf mass per area of A. philoxeroides increased significantly with the increase of soil N:P. In sum, the intraspecific changes of plant functional traits are caused by the changes of soil physical and chemical properties and woody plant coverage with abandoned years.

Functional biogeography studies the spatio-temporal variations in patterns of traits and functional diversity, their ecological determinants and effects on ecosystem functioning. With the exponential growth in trait data, this field has developed rapidly in the recent decades and made major progress in exploring the response of species distribution, community structure and composition, and ecosystem properties on environmental changes based on traits. In this paper, we reviewed core objectives, historical developments, main research advance and future directions in the field of plant functional biogeography. Traits are the focus of research in functional biogeography. Here, we first described major findings on the spatial patterns of key traits in plant organs (i.e. leaves, stems, roots, and flowers, along with fruits and seeds) to the whole plants, and their relationships with environment, showing that traits variations are the results of plant adaptive evolution and environmental filtering. Secondly, we summarized the indicators of functional diversity, assessed the spatial distributions of functional diversity, and identified their determinants. We also summarized the main data sources of traits and related gap-filling approaches. Next, we reviewed trait associations and trade-offs among and within organs as well as in the entire plants, focusing on the global leaf economics spectrums and wood economics spectrum, and pointing out the strategies of plants to obtain and allocate important resource (i.e. carbon, nutrients and water). We summarized how trait-based approaches help to predict species distribution, and the link between trait diversity with ecosystem functions. We highlighted the challenges in current research and emphasized the importance to focus on the coordination and trade-offs among multiple traits along with both inter- and intra-specific trait variation in future research, transferring species-based models to individual-based ones, and to adopt approaches like trait networks to quantify the links among traits and their response to environmental changes, further to explore adaptation of plants across scales. Meanwhile, we suggested potential improvement in application of current research advances, which may be useful in constructing next-generation vegetation models and guiding the function-based conservation of plant diversity in future research.

Aims Leaf traits are closely related to plant light use efficiency and photosynthesis. They can indicate plant adaptation strategies to the environment. Spartina alterniflora is a major alien invasive plant in many coastal wetlands, and it seriously threatens coastal wetland ecosystems in China. Tidal flooding is one of the main limiting factors for the growth and distribution of S. alterniflora in coastal wetlands. However, there has been very little research directly examining the pattern and adaptation mechanism of leaf traits of S. alterniflora along a tidal gradient.

Methods In this study, a tidal elevation control platform was established in Zhangjiang Estuary, Fujian. We studied the response pattern and driving factors of leaf functional traits (length, width, length width ratio, area, dry mass, and specific leaf area) of S. alterniflora to the tidal gradient (relative elevation).

Important findings The results showed that: (1) The leaf length, leaf width, leaf area, and leaf dry mass of S. alterniflora decreased with increasing elevation, whereas the leaf length width ratio increased with increasing elevation. (2) The specific leaf area of S. alterniflora and elevation showed a hump-shaped relationship. (3) The effects of inundation frequency, soil porewater salinity, and soil water content on leaf traits were different. The leaf length, leaf width, leaf area, and leaf dry mass of S. alterniflora increased with increasing inundation frequency and soil water content, but decreased with increasing soil porewater salinity; the leaf length width ratio of S. alterniflora decreased with increasing inundation frequency and soil water content, but increased with increasing soil porewater salinity; the specific leaf area of S. alterniflora increased first and then decreased with increasing inundation frequency, and increased with increasing soil water content. In summary, the patterns and main driving factors of leaf traits of S. alterniflora differed along a tidal gradient, and this finding may be due to differences in the effects of leaf traits on plant physiological processes. Thus, S. alterniflora can adapt to changes in tidal elevation by adjusting leaf traits and their trade-offs. This study provides a new perspective for understanding and predicting the ecological adaptation of S. alterniflora to sea level rise in coastal wetlands.

Aims The subject of plant functional traits, which reflect plant growth and survival strategies, is an important trending topic in plant ecology. In this study, we selected three native warm temperate shrub species in China: Vitex negundo var. heterophylla, Ziziphus jujuba var. spinosa, Grewia biloba var. parviflora and two alien species: Amorpha fruticosa and Rhus typhina, to compare their growth and survival strategies.
Methods The differences in growth strategies were analyzed by measuring plant functional traits. This experiment was carried out at Fanggan ecological experimental station of Shandong University in Jinan. The seeds of five shrubs were germinated and 20 seedlings of each species were planted in pots containing a mixture of sand and humus (2:1, by volume). The leaf structural traits, leaf nitrogen, phosphorus and potassium, chlorophyll content, leaf gas exchange parameters, chlorophyll fluorescence, biomass, and seedling growth parameters were measured.
Important findings Physiological and ecological characteristics of five shrub seedlings were different under the same condition. 1) The alien species, i.e. R. typhina and A. fruticosa, showed high photosynthetic rates and had a strong ability to adjust to the instantaneous change of light intensity, which may be beneficial for plants to make full use of sunflecks under the canopy. The high supporting structure ratio of A. fruticosa is also more conducive to leaf movements, thus adjusting to the changeable light environment. The supporting structure ratio of A. fruticosa was as high as 0.434, which is conducive to its leaf movement and adjustment to the changeable light environment. The high photosynthetic capacity of R. typhina and A. fruticosa was the vital reason for the establishment of the two alien species. 2) The local species V. negundo var. heterophylla and Z. jujuba var. spinosa demonstrated relatively conservative utilization of resources, and in both of them low gas exchange values were measured. However, V. negundo var. heterophylla could make full use of the midday light. 3) G. biloba var. parviflora showed strong gas exchange capacity, and the actual quantum yield of diurnal variation of fluorescence was slow to recover in the afternoon as demonstrated by the chlorophyll fluorescence analysis. In addition, Grewia biloba var. parviflora had the lowest specific leaf mass (44.539 g·m^-2) and chlorophyll a/b (2.215), which confirmed that it is a shade-tolerant plant. Traits such as good seed dispersal ability, leaf heat dissipation ability, conservative light energy utilization strategy, and strong ability to recover after disturbance, help V. negundo var. heterophylla become the dominant species in the warm temperate zone of China. In summary, our study is helpful to understand the growth strategy and niche differentiation mechanisms in several common shrubs of warm temperate zone of China and provides theoretical basis for vegetation restoration, vegetation reconstruction and sustainable development of regional ecological environment.

Aims Trait-trait relationships and trait-environment relationships are critical for understanding species distribution, community assembly and plant strategy to environmental change. Caragana species distribute widely in arid Mongolia Plateau, and shape the alternative distribution along the environmental gradients. To understand the plant strategies to climate and soil, the trait-trait relationships and trait-environmental relationships were documented for Caragana species in Nei Mongol region.
Methods We measured eight morphological and chemical traits from nine Caragana species distributed across 41 sites in Nei Mongol, including plant height (h), leaf dry matter content (LDMC), specific leaf area (SLA), stem tissue density (STD), leaf area (LA), leaf nitrogen content (LNC), leaf phosphorus content (LPC), and leaf nitrogen to phosphorus ratio (N:P). We tested the trait-trait relationships between species and within species, and explored their relationships with aridity, soil nitrogen content and pH at the genus levels.
Important findings We found that the aridity index explained more than 29% of the variation in most functional traits (except N:P), with h, SLA, LA, LNC, and LPC decreased, while LDMC and STD increased with increasing drought. h, SLA, LDMC, STD and LNC were also affected by soil total nitrogen content. However, soil pH explained less for Caragana traits. The synchronous correlations or trade-offs among different functional traits were stronger at the genus level, while the trait-trait relationships within species were weak. There was a consistent increase in h, SLA, LA, LNC and LPC, but a decrease in LDMC and STD to declined aridity. We only observed significant correlations at the within-species level for C. korshinskii and C. microphylla, which were the most widely distributed. Plants with smaller distribution range have weak intraspecific covariation relationships among functional traits, which indicated that the plant economic spectrum theory is not necessarily suitable to explain the utilization of resources and the adaptation strategies of plants to environmental changes at the local scale at the individual level.

Aims The dynamic changes of plant leaf traits during sand dune fixation in semi-arid areas is of significance to reveal the ecologically adaptative strategies of sand plants to environmental changes in the region.
Methods Eleven leaf traits of a typical species, Artemisia ordosica, in the Mau Us Sandy Land, was measured at its four different stages of sand dune fixation (semi-fixed dune, fixed dune, fixed dune with biological soil crusts, fixed dune with abundant herbaceous plants). The variations in the leaf traits and their relationships over different sand-fixation stages were tested using correlation, principal component and similarity analysis.
Important findings (1) The leaf area (LA) and maximum net photosynthetic rate (A_max) in the semi-fixed dune stage were significantly higher than the other three stages of sand dune fixation, leaf carbon content increased significantly and then decreased slightly as the dunes gradually fixed. Leaf phosphorus content at the semi-fixed dune and the fixed dune with biological soil crusts was significantly higher than that at other two stages, and being highest at the semi-fixed dune stage. These variations in leaf traits indicated that A. ordosica tended to enhance photosynthesis for survival in the semi-fixed dune stage. (2) Photosynthesis-related traits of LA and specific leaf area (SLA) were significantly and negatively correlated with physically defense-related structure traits of leaf dry matter content (LDMC) and leaf tissue density, respectively, regardless of the stage of sand dune fixation. The results demonstrated that in order to adapt to the dry environment, the investment in leaf photosynthetic capacity would decrease with the increase of investment in physical defense structure. It also showed that there was a trade-off between the plant growth and defense capability enhancement at different stages of sand dune fixation. (3) The leaf chemical traits were significantly correlated with the leaf morphological and physiological traits. And the leaf traits tended to develop from “rapid investment - return” to “slow investment - return” as sand dune fixed. The results demonstrated that sandy plants could adjust their resource use trade-off strategy to adapt to different environmental changes through leaf traits and interrelationship optimization.

Plant functional traits are the measurable characteristics that indicates plant adaptation to the environment, and understanding the patterns of certain characteristics, and their drivers is an essential component of plant ecology and earth system modeling research. Traditional field-based approaches for characterizing plant functional traits are time-consuming, labor-intensive and expensive, and usually focus on the traits of peak growing season and dominant species, making the scaling extension and spatiotemporal coverage of plant functional traits a great challenge. In contrast, newly emerging multi-scale hyperspectral remote sensing techniques potentially provide new avenues to easily identify and characterize functional traits. Here we first overview the principles and brief history of hyperspectral remote sensing technology for plant functional traits monitoring. Then, we detailed the principal methods for modelling the spectral-trait relationships, including empirical and semi-empirical statistical methods and inversion methods relying on physical-based modelling, among which the statistical partial least squares regression is widely used. We then used case studies to demonstrate the application while illustrating the remaining problems of plant functional traits monitoring using the hyperspectral remote sensing techniques respectively at leaf, community and landscape scales. Finally, we highlight four important future directions to advance hyperspectral remote sensing of plant functional traits, including: 1) exploring the generalizability and underlying mechanisms of spectral-trait modelling; 2) developing novel, transparent methodology that scales the spectral-trait relationships from leaf, canopy to satellite levels; 3) elucidating the pattern and drivers of remotely sensed plant functional traits and diversity across various spatiotemporal scales; and 4) investigating the linkage among environment, plant functional diversity, biodiversity and ecosystem functioning.

Aims In order to explore the effects of different water and salt environments on the plant functional traits and their ecological stoichiometric characteristics at the lakeshore zone of Bosten Lake. The dominant plants and soil environmental factors in this area were selected to clarify the strategy of plant adaptation to the environments in this region.

Methods Eighteen sample plots were set up to investigate plant diversity. A total of 24 plant species including 8 shrubs and 16 herbaceous species were examined. The relationship between functional traits of plant leaves and soil environmental factors was tested using redundancy analysis method.

Important findings Our results showed that leaf functional traits varied considerably with the increasing water and salt content. Among plant traits, the chlorophyll content (SPAD), leaf thickness (LT) and specific leaf area (SLA) were the greatest in low water and salt environments, while the leaf water content (LWC), leaf dry matter content (LDMC) and leaf dry mass (LDM) were greater in medium and high water and salt environments. The content of carbon (C), nitrogen (N) and phosphorus (P) of plant leaves and their stoichiometric ratios were highly variable, with the C:N being 9.35-26.51 and the range of C:P being 50.13-228.95. The range of N:P was 2.31-11.99, with the largest variation in C:P. The Leaf C content was significantly and positively correlated with LT, LDMC and LDM, and leaf N content was significantly and positively correlated with SPAD and LT, while leaf P content was significantly and positively correlated with LWC. Whereas, C:N and C:P were both significantly and positively correlated with LDMC, while N:P was not correlated with any of the leaf functional traits. SLA was not correlated with any of the leaf ecological stoichiometric characteristics. The correlation between environmental factors and the functional traits of the dominant plant leaves revealed that the environmental factors affecting the functional traits of plants differed between species.

Aims The lamina and petiole of a leaf are closely related in structure and function, of which the variation and correlation are important for understanding the strategies of biomass allocation at the leaf level.

Methods In this study, we sampled Betula platyphylla, Tilia amurensisand Acer pictum subsp. mono in a broadleaved Korean pine (Pinus koraiensis) forest in Northeast China and explored effects of species, tree size and canopy position on variations in and correlations between lamina and petiole traits. For each species, we selected 10 trees for small (diameter at breast height (DBH): 1-6 cm), intermediate (DBH: 15-20 cm), and large sizes (DBH: 35-45 cm), respectively. For the large-sized trees, we took canopy position into account. We measured lamina area (LA), lamina dry mass (LDM), petiole length (PL), and petiole dry mass (PDM).

Important findings (1) The four traits significantly varied with species and tree size. PL and PDM of the small trees were significantly lower than those of large trees for the three species. LDM of the small trees was significantly less than that of the large trees for T. amurensis and A. pictum subsp. mono, while LA of the small trees was significantly greater than that of the large trees for B. platyphyllaand T. amurensis. For the large trees, the effect of canopy position on the variations in the four traits was species-depended. (2) There was a significant allometric scaling relationship between the lamina and petiole traits for all the three species. The regression slopes ranked as T. amurensis > B. platyphylla> A. pictum subsp. mono; the slopes for B. platyphyllaranked as small size > large size > intermediate size, while the slopes for the large-sized trees were the greatest among different tree sizes for T. amurensisand A. pictum subsp. mono. Canopy position had no significant effect on the regression slope for the large-sized trees. These results showed that species and tree size significantly influenced the variations in and correlations between the lamina and petiole traits for the three temperate tree species, while canopy position had little effect for the large-sized trees.

Aims We address the issue of adapting patch pattern for improved plant biodiversity conservation in sandy grasslands by assessing the role of edge type in the influences of patch pattern on plant diversity and functional traits. We test the hypotheses that plant richness, alpha and beta diversity would vary according to patch pattern but that these effects would vary according to edge type, through adaptation of plant functional traits. Methods Jointing satellite imagery interpretation, 705 plots from two-year surveys and spatial analysis, patch edges in center Hunshandak Sandland were categorized into four types. Duncan’s differences were tested across four edge types. Pearson’s correlation and redundancy analysis (RDA) were used to discern the patch contributions. Important findings Plant richness and diversity indices are closely related with patch patterns, these relations vary significantly across edge types, demonstrating different functional traits. For inward edge, edge metrics attributes to richness reduction and C₄ plant proportion, mean perimeter-area ratio (MPAR) positively related to nitrogen-fixed species proportion. For outward edge, mean patch fractal dimension (MPFD) negatively related to richness, MPAR positively related to the proportion of nitrogen-fixing species, edge metrics positively related to C₄ proportion. For inward nucleating edge, MPAR, total edge (TE) and landscape area (TLA) positively related to perennial plants, TE and TLA positively linked to insect-pollination plants. For outward nucleating edge, angle and pattern metrics positively related to Shannon-Wiener and Simpson index, negatively related to Pielou index, richness and animal-seed dispersing plants. Patch pattern distressing plant diversity through edge effects can be moderately interpreted by plant practical qualities and edge metrics. It must be well thought-out in landscape management, vegetation restoration and biodiversity conservation.

Aims Understanding the trade-offs between leaf functional traits has long been a hot topic in ecological research.

Methods In a broadleaved Korean pine (Pinus koraiensis) forest and a spruce-fir valley forest in the Liangshui National Nature Reserve, Heilongjiang Province, we measured 5 leaf economic traits and 4 leaf defense traits for seedlings of 8 tree species and 11 shrub species, to evaluate trait variation across species life forms and forest types, as well as trait correlations.

Important findings There was no significant difference in leaf traits between the seedlings of trees and shrubs. The total phenolic content and tannin content of plants in the spruce-fir valley forest were significantly higher than those in broadleaved Korean pine forest. Compared with broadleaved Korean pine forest, the spruce-fir valley forest has lower under-canopy light intensity but higher air and soil moisture, which is more conducive to the aggregation of natural enemies. This stronger biological interaction may in turn drives seedlings to invest more on their defense traits in spruce-fir forest. Leaf chlorophyll content was positively correlated with specific leaf area, leaf nitrogen and phosphorus content. Leaf nitrogen content was positively correlated with leaf phosphorus content. Moreover, there was a significant and positive correlation between leaf defense traits. Leaf chlorophyll and nitrogen content were negatively correlated with total phenolic content, tannin content and content of flavonoids. This suggests the existence of a trade-off between leaf carbon economics and defense. The seedlings of trees and shrubs had similar carbon economics strategies. The results of this study have implications for predicting forest dynamics and community composition based on leaf functional traits.

Aims At leaf level, trade-offs between petiole (supporting structure) and lamina (assimilation structure) are influenced by several factors. Here, we aim to provide insight into the growth features and life history strategies of plants by exploring the trade-offs between petiole and lamina traits for different functional plants in Northeast China.

Methods We measured leaf traits in three life-form plants (tree, shrub, herb) of a broadleaved Korean pine (Pinus koraiensis) forest in Xiao Hinggan Mountains, China. The least significant difference method was used to compare the variation of leaf traits among the three life forms. Trade-offs between lamina and petiole traits were estimated by using standardized major axis method for the three groups, in terms of their life form, leaf type, and shade tolerance.

Important findings Significant allometric scaling relationships were found between lamina traits and petiole dry mass in all life forms, leaf types and different shade tolerant tree species, with slopes significantly departing from 1.0. As petiole dry mass increased, the lamina fresh mass and lamina dry mass of trees increased more significant than shrubs and herbs, but tree petioles can support the smallest leaf area for a given petiole dry mass. The regression slope of lamina area-petiole dry mass for simple-leaved species was significantly greater than that of compound-leaved species, but the regression slope of lamina fresh mass-petiole dry mass was opposite, and simple-leaved species had greater lamina dry mass at a given petiole dry mass than compound-leaved species. Shade tolerant tree species were observed to have larger lamina area and greater lamina fresh mass at a given petiole dry mass than shade intolerant tree species. Moreover, the slope of petiole biomass allocation ratio (petiole dry mass/leaf dry mass)-lamina trait was greater than 0 for shade intolerant tree species and less than 0 for shade tolerant tree species. Our results suggested trade-offs exist between leaf properties (leaf area, leaf fresh mass, leaf dry mass) and petiole traits (petiole dry mass), which can be varied for plants with different life form, leaf type, and shade tolerance, thus to some extent, revealed the growth features and life history strategies of different functional plants.