Temporal intraspecific trait variability drives responses of functional diversity to interannual aridity variation in grasslands

Interannual climate variation alters functional diversity through intraspecific trait variability and species turnover. We examined these diversity elements in three types of grasslands in northern China, including two temperate steppes and an alpine meadow. We evaluated the differences in community‐weighted means (CWM) of plant traits and functional dispersion (FDis) between 2 years with contrasting aridity in the growing season. Four traits were measured: specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen concentration (LNC), and the maximum plant height (H). CWM for SLA of the alpine meadow increased in the dry year while that of the temperate steppe in Qinghai showed opposing trends. CWM of LDMC in two temperate steppes became higher and CWM of LNC in all grasslands became lower in the dry year. Compared with the wet year, FDis of LDMC in the alpine meadow and FDis of LNC in the temperate steppe in Qinghai decreased in the dry year. FDis of H was higher in the dry year for two temperate steppes. Only in the temperate steppe in Qinghai did the multi‐FDis of all traits experience a significant increase in the dry year. Most of the changes in CWM and FDis between 2 years were explained by intraspecific trait variation rather than shifts in species composition. This study highlights that temporal intraspecific trait variation contributes to functional responses to environmental changes. Our results also suggest it would be necessary to consider habitat types when modeling ecosystem responses to climate changes, as different grasslands showed different response patterns.     

Potential trajectories of old‐growth Neotropical forest functional composition under climate change

Quantifying relationships between plant functional traits and abiotic gradients is valuable for evaluating potential responses of forest communities to climate change. However, the trajectories of change expected to occur in tropical forest functional characteristics as a function of future climate variation are largely unknown. We modeled community level trait values of Costa Rican rain forests as a function of current and future climate, and quantified potential changes in functional composition. We calculated per‐plot community weighted mean (CWM) trait values for leaf area (LA), specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen (N) and phosphorus (P) content, and wood basic specific gravity (WSG), for tree and palm species in 127 0.25 ha plots. We modeled the response of CWM traits to current temperature and precipitation gradients using generalized additive modeling. We then predicted and mapped CWM traits values under current and future climate, and quantified potential changes under a global warming scenario (RCP8.5, year 2050). We calculated the area within the multi trait functional space occupied by forest plots under both current and future climate, and determined potential changes in functional space occupied by forest plots. Overall, precipitation predicted CWM traits better than temperature. Models indicated increases in CWM SLA, N and P, and a decrease in CWM LDMC under climate change. Lowland forest communities converged on a single direction of change towards more acquisitive CWM trait values, indicating a change in forest functional composition resulting from a changed climate. Functional space occupied by forest plots was reduced by 50% under the future climate. Functional composition changes may have further effects on forests ecosystem services. Assessing functional trait spatial‐gradients can help bridge the gap between species‐based biogeography and biogeochemical approaches to strengthen biodiversity and ecosystem services conservation efforts.     

Contrasting effects of plant inter‐ and intraspecific variation on community trait responses to restoration of a sandy grassland ecosystem

Changes in plant community traits along an environmental gradient are caused by interspecific and intraspecific trait variation. However, little is known about the role of interspecific and intraspecific trait variation in plant community responses to the restoration of a sandy grassland ecosystem. We measured five functional traits of 34 species along a restoration gradient of sandy grassland (mobile dune, semi‐fixed dune, fixed dune, and grassland) in Horqin Sand Land, northern China. We examined how community‐level traits varied with habitat changes and soil gradients using both abundance‐weighted and non‐weighted averages of trait values. We quantified the relative contribution of inter‐ and intraspecific trait variation in specific leaf area (SLA), leaf dry matter content (LDMC), leaf carbon content (LCC), leaf nitrogen content (LNC), and plant height to the community response to habitat changes in the restoration of sandy grassland. We found that five weighted community‐average traits varied significantly with habitat changes. Along the soil gradient in the restoration of sandy grassland, plant height, SLA, LDMC, and LCC increased, while LNC decreased. For all traits, there was a greater contribution of interspecific variation to community response in regard to habitat changes relative to that of intraspecific variation. The relative contribution of the interspecific variation effect of an abundance‐weighted trait was greater than that of a non‐weighted trait with regard to all traits except LDMC. A community‐level trait response to habitat changes was due largely to species turnover. Though the intraspecific shift plays a small role in community trait response to habitat changes, it has an effect on plant coexistence and the maintenance of herbaceous plants in sandy grassland habitats. The context dependency of positive and negative covariation between inter‐ and intraspecific variation further suggests that both effects of inter‐ and intraspecific variation on a community trait should be considered when understanding a plant community response to environmental changes in sandy grassland ecosystems.     

Direct and indirect facilitation affect community productivity through changes in functional diversity in an alpine system

Background and AimsFacilitation is an important ecological process for plant community structure and functional composition. Although direct facilitation has accrued most of the evidence so far, indirect facilitation is ubiquitous in nature and it has an enormous potential to explain community structuring. In this study, we assess the effect of direct and indirect facilitation on community productivity via taxonomic and functional diversity.MethodsIn an alpine community on the Tibetan Plateau, we manipulated the presence of the shrub Dasiphora fruticosa and graminoids in a fenced meadow and a grazed meadow to quantify the effects of direct and indirect facilitation. We measured four plant traits: height, lateral spread, specific leaf area (SLA) and leaf dry matter content (LDMC) of forbs; calculated two metrics of functional diversity [range of trait and community-weighted mean (CWM) of trait]; and assessed the responses of functional diversity to shrub facilitation. We used structural equation modelling to explore how shrubs directly and indirectly drove community productivity via taxonomic diversity and functional diversity.Key ResultsWe found stronger effects from herbivore-mediated indirect facilitation than direct facilitation on productivity and taxonomic diversity, regardless of the presence of graminoids. For functional diversity, the range and CWM of height and SLA, rather than lateral spread and LDMC, generally increased due to direct and indirect facilitation. Moreover, we found that the range of traits played a primary role over taxonomic diversity and CWM of traits in terms of shrub effects on community productivity.ConclusionsOur study reveals that the mechanism of shrub direct and indirect facilitation of community productivity in this alpine community is expanding the realized niche (i.e. expanding range of traits). Our findings indicate that facilitators might increase trait dispersion in the local community, which could alleviate the effect of environmental filters on trait values in harsh environments, thereby contributing to ecosystem functioning.     

Functional Trait Changes,Productivity Shifts and Vegetation Stability in Mountain Grasslands during a Short-Term Warming

Plant functional traits underlie vegetation responses to environmental changes such as global warming, and consequently influence ecosystem processes. While most of the existing studies focus on the effect of warming only on species diversity and productivity, we further investigated (i) how the structure of community plant functional traits in temperate grasslands respond to experimental warming, and (ii) whether species and functional diversity contribute to a greater stability of grasslands, in terms of vegetation composition and productivity. Intact vegetation turves were extracted from temperate subalpine grassland (highland) in the Eastern Pyrenees and transplanted into a warm continental, experimental site in Lleida, in Western Catalonia (lowland). The impacts of simulated warming on plant production and diversity, functional trait structure, and vegetation compositional stability were assessed. We observed an increase in biomass and a reduction in species and functional diversity under short-term warming. The functional structure of the grassland communities changed significantly, in terms of functional diversity and community-weighted means (CWM) for several traits. Acquisitive and fast-growing species with higher SLA, early flowering, erect growth habit, and rhizomatous strategy became dominant in the lowland. Productivity was significantly positively related to species, and to a lower extent, functional diversity, but productivity and stability after warming were more dependent on trait composition (CWM) than on diversity. The turves with more acquisitive species before warming changed less in composition after warming. Results suggest that (i) the short-term warming can lead to the dominance of acquisitive fast growing species over conservative species, thus reducing species richness, and (ii) the functional traits structure in grassland communities had a greater influence on the productivity and stability of the community under short-term warming, compared to diversity effects. In summary, short-term climate warming can greatly alter vegetation functional structure and its relation to productivity.     

The role of fire in structuring trait variability in Neotropical savannas

Intraspecific trait variability plays a fundamental role in community structure and dynamics; however, few studies have evaluated its relative importance to the overall response of communities to environmental pressures. Since fire is considered a key factor in Neotropical savannas, we investigated to what extent the functional effects of fire in a Brazilian savanna occurs via intra- or interspecific trait variability. We sampled 12 traits in communities subjected to three fire regimes in the last 12 years: annual, biennial, and protected. To evaluate fire’s relative effects, we fitted a general linear mixed models with species as random and fire as fixed factors, using: (1) all species in the communities (i.e., considering intra- and interspecific variabilities); (2) 18 species common to all fire regimes (i.e., intraspecific variability only); and (3) all species with their overall average trait values (i.e., interspecific variability only). We assessed the relative role of intra- or interspecific variability by comparing the significance of each trait in the three analyses. We also compared the within and between fire variabilities with a variance component analysis. Five traits presented larger intraspecific than interspecific variability, and the main effect of fire occurred at the intraspecific level. These results confirm that it is important to consider intraspecific variability to fully understand fire-prone communities. Moreover, trait variability was larger within than among fire regimes. Thus, fire may act more as an external filter, preventing some of the species from the regional pool from colonizing the cerrado, than as an internal factor structuring the already filtered cerrado communities.     

Incorporating intraspecific variation in tests of trait-based community assembly

Environmental filtering and niche differentiation are processes proposed to drive community assembly, generating nonrandom patterns in community trait distributions. Despite the substantial intraspecific trait variation present in plant communities, most previous studies of trait-based community assembly have used species mean trait values and therefore not accounted for intraspecific variation. Using a null model approach, I tested for environmental filtering and niche differentiation acting on three key functional traits??vegetative height, specific leaf area (SLA), and leaf dry matter content (LDMC)??in old-field plant communities. I also examined how accounting for intraspecific variation at the among-plot and individual levels affected the detection of nonrandom assembly patterns. Tests using fixed species mean trait values provided evidence of environmental filtering acting on height and SLA and niche differentiation acting on SLA. Including plot-level intraspecific variation increased the strength of these patterns, indicating an important role of intraspecific variation in community assembly. Tests using individual trait data indicated strong environmental filtering acting on all traits, but provided no evidence of niche differentiation, although these signals may have been obscured by the effects of dispersal limitation and spatial aggregation of conspecific individuals. There was also strong evidence of nonrandom assembly of individuals within single species, with the strength of environmental filtering varying among species. This study demonstrates that, while analyses using fixed species mean trait values can provide insights into community assembly processes, accounting for intraspecific variation provides a more complete view of communities and the processes driving their assembly.     

Assessing the functional turnover of species assemblages with tailored dissimilarity matrices

It is often suggested that community functional diversity is an appropriate predictive measure of ecosystem functioning, particularly if relevant species traits for the ecological property of interest are carefully selected. However, methods for selecting traits are often based on expert knowledge or on theoretical models of ecosystem functioning, but usually do not include explicitly developed quantitative procedures. Here we propose to construct a so‐called ‘tailored dissimilarity matrix’ between species assemblages to emphasize their functional turnover in response to some user‐defined ecological property. First, a subset of community weighted mean trait values (CWM) is selected by stepwise regression on the ecological process of interest. The selected CWM values are then replaced by the residuals of the least‐squares regressions of each single CWM on the ecological process of interest and pairwise Euclidean distances between the residual values at each sampling site are calculated. We illustrate the advantages of the tailored approach using two distinct plant and bee communities under contrasting fire regimes in temperate forests of southern Switzerland. Our results demonstrated that, unlike for the original CWM values, the tailored approach optimized the degree of functional differentiation among bee and plant species assemblages, i.e. the species functional turnover, with respect to different fire regimes.     

Dry calcareous grasslands from two neighboring biogeographic regions: relationship between plant traits and rarity

European dry grasslands formed of the Festuco-Brometea type are among the most diverse plant communities within agricultural landscapes. We examined floristic composition, functional trait structure and threatened species occurrence in grasslands of this type from in two distinct biogeographic regions, Dinaric (NW Balkan) and the Central European. In the Central European region this type of grassland is threatened by a decline in traditional extensive management. We tested, if differences in the level of threat between regions are matched by differences in community-weighted means for resource use strategy traits and occurrence of Red List (threatened) species. We then tested if threatened species differed in their traits from other species and if threatened species richness was related to CWM for resource use strategy traits. The communities from the Central European region had significantly higher SLA and lower LDMC, which perhaps reflects an increase in intensive agriculture promoting fast-growing species. Threatened species occurrence did not differ significantly between regions, but threatened species richness was significantly negatively correlated with CWM for height and SLA. This may suggest that threatened species are less likely to occur in high productivity communities where light competition is intense. This study provides initial evidence that changes in CWM for resource use strategy traits may provide a useful means for predicting threatened species loss in dry grassland ecosystems.     

Disturbance regime changes the trait distribution,phylogenetic structure and community assembly of tropical rain forests

A rapidly increasing effort to merge functional community ecology and phylogenetic biology has increased our understanding of community assembly. However, studies using both phylogenetic‐ and trait‐based methods have been mainly conducted in old‐growth forests, with fewer studies in human‐disturbed communities, which play an increasingly important role in providing ecosystem services as primary forests are degraded. We used data from 18 1‐ha plots in tropical old‐growth forests and secondary forests with different disturbance histories (logging and shifting cultivation) and vegetation types (tropical lowland and montane forests) on Hainan Island, southern China. The distributions of 11 functional traits were compared among these six forest types. We used a null model approach to assess the effects of disturbance regimes on variation in response and effect traits and community phylogenetic structure across different stem sizes (saplings, treelets, and adult trees) and spatial scales (10–50 m). We found significant differences in the distribution of functional traits in highly disturbed lowland sites versus other forest types. Many individuals in highly disturbed lowland sites were deciduous, spiny, with non‐fleshy fruits and seeds dispersed passively or by wind, and low SLA. The response traits of coexisting species were clustered in all sites except for highly disturbed lowland sites where evenness was evident. There were different distributions of effect traits for saplings and treelets among different forest types but adult trees showed stronger clustering of trait values with increasing spatial scale among all forest types. Phylogenetic clustering predominated across all size classes and spatial scales in the highly disturbed lowland sites, and evenness in other forest types. High disturbance can lead to abiotic filtering, generating a community dominated by closely related species with disturbance‐adapted traits, where biotic interactions play a relatively minor role. In lightly disturbed and old growth forests, multiple processes simultaneously drive the community assembly, but biotic processes dominate at the fine scale.     

Trait‐mediated community assembly: distinguishing the signatures of biotic and abiotic filters

Conflicting hypotheses predict how traits mediate species establishment and community assembly. Traits of newly establishing individuals are predicted to converge, or be more similar to the resident, preexisting community, when the biotic or abiotic environment favors a single best phenotype, but are predicted to diverge when trait differences reduce competitive interactions. We tested these competing hypotheses using transplant seedlings in an old‐field environment, and assessed the contribution of inter‐ and intra‐specific transplant trait variation to community‐level patterns. Using a soil moisture gradient and resident plant removals, we determined when traits of newly‐establishing plants converge or diverge from the resident community by calculating community weighted mean traits for transplant and resident communities. We saw evidence of environmentally‐ and competitively‐driven trait shifts that resulted in both trait convergence and divergence from the resident community, whose traits reflect the combined effects of both drivers. Leaf dry matter content (LDMC) of transplants diverged in the presence of competition, whereas plant height and stem‐specific density (SSD) showed the opposite pattern, converging with the resident community in their presence. Specific leaf area (SLA) shifted with competition but did not reflect resident community SLA. All transplant traits were influenced by soil moisture, often in an interaction with competition, indicating that the strength of convergence or divergence is contingent on the abiotic environment. Intraspecific differences in transplant traits among treatments were evident in three of four traits; intraspecific height and SLA trends mirrored transplant community‐level trends, whereas intraspecific shifts in SSD were distinct from community‐level trends. Our study shows competition between plant species may cause traits of newly establishing plants to converge with the resident community, as frequently as it selects for trait divergence. These opposing effects of competition suggest that it plays a pervasive role in both intraspecific and species‐level trait differences among communities.     

Community Functional Responses to Soil and Climate at Multiple Spatial Scales: When Does Intraspecific Variation Matter?

Despite increasing evidence of the importance of intraspecific trait variation in plant communities, its role in community trait responses to environmental variation, particularly along broad-scale climatic gradients, is poorly understood. We analyzed functional trait variation among early-successional herbaceous plant communities (old fields) across a 1200-km latitudinal extent in eastern North America, focusing on four traits: vegetative height, leaf area, specific leaf area (SLA), and leaf dry matter content (LDMC). We determined the contributions of species turnover and intraspecific variation to between-site functional dissimilarity at multiple spatial scales and community trait responses to edaphic and climatic factors. Among-site variation in community mean trait values and community trait responses to the environment were generated by a combination of species turnover and intraspecific variation, with species turnover making a greater contribution for all traits. The relative importance of intraspecific variation decreased with increasing geographic and environmental distance between sites for SLA and leaf area. Intraspecific variation was most important for responses of vegetative height and responses to edaphic compared to climatic factors. Individual species displayed strong trait responses to environmental factors in many cases, but these responses were highly variable among species and did not usually scale up to the community level. These findings provide new insights into the role of intraspecific trait variation in plant communities and the factors controlling its relative importance. The contribution of intraspecific variation to community trait responses was greatest at fine spatial scales and along edaphic gradients, while species turnover dominated at broad spatial scales and along climatic gradients.     

Drivers of within-tree leaf trait variation in a tropical planted forest varying in tree species richness

In plant ecology, community-weighted trait means are often used as predictors for ecosystem functions. More recently, also within-species trait variation has been confirmed to contribute to ecosystem functioning. We here go even further and assess within-individual trait variation, assuming that every leaf in a plant individually adjusts to its micro-environment. Using forest plots varying in tree species richness (Sardinilla experiment, Panama), we analysed how leaf traits within individual trees vary along the vertical crown gradient. Furthermore, we tested whether niche partitioning in mixed stands results in a decrease of within-species leaf trait variation and whether niche partitioning can be also observed at the level of individual trees. We focused on leaf traits that describe the growth strategy along the conservative-acquisitive spectrum of growth. We found a decrease in within-species variation of specific leaf area (SLA) with increasing neighbourhood species richness. Both sampling height and local neighbourhood richness contributed to explaining within-species leaf trait variation, which however, varied in importance among different species and traits. With increasing sampling height, leaf dry matter content (LDMC), carbon to nitrogen ratio and lignin content increased, while leaf nitrogen concentration (leaf N), SLA, cellulose and hemicellulose decreased. Variation in leaf N decreased with increasing neighbourhood species richness, while the magnitude of within-individual variation of most traits was unaffected by neighbourhood species richness. Our results suggest an increased niche partitioning with increasing species richness both in a plant community and at the level of individual plants. Our findings highlight the importance of including within-individual trait variation to understand biodiversity-ecosystem functioning relationships.     

Long-term warming affects ecosystem functioning through species turnover and intraspecific trait variation

Effects of climate change on natural ecosystems can be mediated by ecological processes, but also by rapid evolutionary adaptations and/or non-heritable trait changes in organisms. So far, most studies testing the importance of inter- versus intraspecific changes for how communities and their functioning responds to climate change are either short-term laboratory experiments in highly controlled (artificial) environments, or long-term field surveys suffering from lack of experimental manipulation. Here, we quantified how community composition and functioning has changed in response to long-term warming, including the potential direct and indirect effects via immediate and delayed physiological, non-heritable plastic, ecological, evolutionary and eco-evolutionary responses. We used a site-for-time approach, sampling sites in an artificially heated basin and a nearby area to quantify how >30 years of experimental warming in situ affects benthic grazer communities and traits of grazer taxa, as well as their contribution to a key ecosystem function: grazing on filamentous algae. The community composition shifted with warming, because a non-native species was highly common, and taxa with higher mobility, became more common in the heated areas compared to the control sites. Warming altered community functioning but the underlying mechanisms varied between traits: increased metabolism was caused by intraspecific trait change, while increased grazing rate was mainly driven by species turnover. Our results suggest that both population- and community-level processes mediate the responses of natural communities to long-term environmental change, and that the ongoing warming of coastal waters is likely to alter the functioning of key marine ecosystems.     

A community‐level test of the leaf‐height‐seed ecology strategy scheme in relation to grazing conditions

Question: Is the assumption of trait independence implied in Westoby's (1998) leaf‐height‐seed (LHS) ecology strategy scheme upheld in a Mediterranean grazing system dominated by annuals? Is the LHS approach applicable at the community level? Location: Northern Israel. Methods: LHS traits (specific leaf area [SLA], plant height and seed mass), and additional leaf traits (leaf dry matter content [LDMC], leaf area, and leaf content of nitrogen [LNC], carbon [LCC], and phosphorus [LPC]), were analyzed at the species and community levels. Treatments included manipulations of grazing intensity (moderate and heavy) and protection from grazing. We focused on species comprising 80% of biomass over all treatments, assuming that these species drive trait relationships and ecosystem processes. Results: At the species level, SLA and seed mass were negatively correlated, and plant height was positively correlated to LCC. SLA, seed mass, and LPC increased with protection from grazing. At the community level, redundancy analysis revealed one principal gradient of variation: SLA, correlated to grazing, versus seed mass and plant height, associated with protection from grazing. We divided community functional parameters into two groups according to grazing response: (1) plant height, seed mass, LDMC, and LCC, associated with protection from grazing, and (2) SLA, associated with grazing. Conclusions: The assumption of independence between LHS traits was not upheld at the species level in this Mediterranean grazing system. At the community level, the LHS approach captured most of the variation associated with protection from grazing, reflecting changes in dominance within the plant community.     

Reprint of: Drivers of within-tree leaf trait variation in a tropical planted forest varying in tree species richness

In plant ecology, community-weighted trait means are often used as predictors for ecosystem functions. More recently, also within-species trait variation has been confirmed to contribute to ecosystem functioning. We here go even further and assess within-individual trait variation, assuming that every leaf in a plant individually adjusts to its micro-environment. Using forest plots varying in tree species richness (Sardinilla experiment, Panama), we analysed how leaf traits within individual trees vary along the vertical crown gradient. Furthermore, we tested whether niche partitioning in mixed stands results in a decrease of within-species leaf trait variation and whether niche partitioning can be also observed at the level of individual trees. We focused on leaf traits that describe the growth strategy along the conservative-acquisitive spectrum of growth. We found a decrease in within-species variation of specific leaf area (SLA) with increasing neighbourhood species richness. Both sampling height and local neighbourhood richness contributed to explaining within-species leaf trait variation, which however, varied in importance among different species and traits. With increasing sampling height, leaf dry matter content (LDMC), carbon to nitrogen ratio and lignin content increased, while leaf nitrogen concentration (leaf N), SLA, cellulose and hemicellulose decreased. Variation in leaf N decreased with increasing neighbourhood species richness, while the magnitude of within-individual variation of most traits was unaffected by neighbourhood species richness. Our results suggest an increased niche partitioning with increasing species richness both in a plant community and at the level of individual plants. Our findings highlight the importance of including within-individual trait variation to understand biodiversity-ecosystem functioning relationships.     

亚热带常绿落叶阔叶混交林植物功能性状的种间和种内变异

不同物种间的功能性状差异是自然生态系统中物种共存的基础, 而物种内个体间的性状变异对物种的共存和分布同样具有重要作用。本文以湖北星斗山自然保护区亚热带常绿落叶阔叶混交林内28种主要树种(通过物种多度排序获得, 其中常绿和落叶树种各14种)为研究对象, 探讨不同叶习性树种的4种功能性状(比叶面积、叶干物质含量、叶面积和比茎密度)在种间和种内的差异程度。结果表明: (1)常绿和落叶树种在4种功能性状上均存在显著差异, 常绿树种的比叶面积和叶面积显著低于落叶树种, 但叶干物质含量和比茎密度则显著高于落叶树种; (2)比叶面积的变化主要来源于叶习性(57.49%), 叶面积变化主要来源于种间(66.80%)和种内变异(27.52%), 叶干物质含量的变化主要来源于种间(38.12%)和种内(33.88%)变异, 但比茎密度的变化主要来源于种内变异(51.50%), 其次为种间变异(32.52%); (3)常绿和落叶树种种间水平的性状相关性可能掩盖各功能性状之间的相关性。种内变异能够显著影响群落间的植物功能性状差异, 但不同功能性状的种内变异程度存在差异。     

油松叶功能性状分布特征及其控制因素

植物叶功能性状能够直接或间接反应植物对环境的适应策略,这种适应策略会间接影响植物的生长、繁殖和生存。目前已有大量关于植物叶功能性状与环境间关系的研究,但这些研究多使用性状平均值代替物种,忽略了性状的种内变化。油松是我国重要的造林树种,对我国陆地生态系统起着重要的作用,研究其叶功能性状与环境的关系有助于更好的的理解种内功能性状与环境间的关系。于2014年6—9月对辽宁、内蒙、北京、山西、陕西、宁夏、青海等地天然油松进行采样并对其重要的8个叶功能性状的分布特征及主控环境因子进行了研究,结果表明:1)油松各叶性状值存在较大的种内变异系数(4.82%—25.85%),除1年生叶碳含量(LCC)油松各叶功能性状值在不同研究地点间差异显著(P0.05);2)油松叶长(LL)、叶厚(LT)、比叶面积(SLA)、气孔密度(SD)、叶氮含量(LNC)存在较弱的经度格局,LT、SD、LNC存在较弱的纬度格局(0.05R~20.3),水热条件的变化以及较大的局部效应是造成这种格局的可能原因;3)控制油松各叶性状分布的主要环境因子各不相同,其中LL主要受到年平均降水量和海拔高度的影响;LT主要受到年均温和土壤体积含水率的影响;SLA主要受到年平均降水量和土壤氮含量的影响;叶干物质含量(LDMC)主要受到水因子的影响;SD主要受到海拔高度的影响;LNC主要受到海拔和水因子的影响;叶磷含量(LPC)主要受到土壤磷含量的影响。     

Leaf trait co‐variation,response and effect in a chronosequence

Question: Is there any generality in terms of leaf trait correlations and the multiple role of leaf traits (response to and/or effect on) during secondary succession? Location: A secondary successional sere was sampled at four different ages since abandonment from several years to nearly 150 years on the Loess Plateau of northwestern China. Method: Specific leaf area (SLA), leaf mass per area (LMA), leaf nitrogen (N_mass, N_area), leaf phosphorus (P_mass, P_area) and leaf dry matter content (LDMC) were measured for all species recorded in the successional sere. Above‐ground net primary productivity (ANPP) and specific rate of litter mass loss (SRLML) were measured as surrogates for ecosystem properties. Soil total carbon (C) and nitrogen (N) were measured in each stage. Leaf traits were related to ecosystem properties and soil nutrient gradients, respectively. Results: LMA is correlated with N_area and P_area' and negatively with N_mass. Correlation between N_area and P_area was higher than between N_mass and P_mass. At the community level, field age, community hierarchy and their interaction explain 64.4 ‐ 93.5% of the variation in leaf traits. At the species level, field age explains 22.4 ‐ 45.5% of the variation in leaf traits (excl. P_area) while plant functional group has a significant effect only for N_mass. LDMC is correlated with ANPP and negatively with SRLML; P_mass is correlated with SRLML. Conclusions: Mean values of LMA, N_mass and N_area are close to the worldwide means, suggesting that large‐scale climate has a profound effect on leaf mass and leaf nitrogen allocation, while environmental gradients represented by succession have little influence on leaf‐trait values. Correlations between leaf traits, such as LMA‐N_area, LMA‐P_area and LMA‐N_mass shown in previous studies, are confirmed here. Although none of the leaf traits is proved to be both a response trait and an effect trait independent of time scale and community hierarchy, mass‐based leaf N is likely a sensitive response trait to soil C and N gradients. In addition, LDMC can be a marker for ANPP and SRLML, while mass‐based leaf P can be a marker for SRLML.     

柯-青冈常绿阔叶林优势树种叶片性状变异及适应策略

厘清叶片功能性状的变异及性状间的权衡关系，对揭示植物对环境变化的响应及适应策略具有重要意义。以中亚热带柯(Lithocarpus glaber)-青冈(Cyclobalanopsis glauca)常绿阔叶林为对象，测量了1 hm²固定监测样地内6个优势树种的叶面积(LA)、比叶面积(SLA)、干物质含量(LDMC)、叶片厚度(LT)、叶片碳(LC)、叶片氮(LN)、叶片磷(LP)含量和叶片碳氮比(LC ∶ LN)8个功能性状，采用多重比较、主成分分析(PCA)法分析了群落叶片功能性状的生活型、种内和种间变异及性状间关系。结果表明：(1)群落内叶片功能性状种内、种间差异显著，变异中等(CV： 0.02-0.59)，其结构性状的可塑性较化学性状保守，变异格局符合"性状空间变异分割假说"；针叶树种的LA、SLA显著低于阔叶树种，常绿树种的LC和LDMC最小，而落叶树种的SLA、LN和LP最大以及LT和LC ∶ LN最小。(2)群落叶片功能性状变异主要来源于生活型和种间变异，种内变异亦有显著贡献；生活型对多数性状的贡献率较大，其对LDMC、LC ∶ LN的贡献分别高达93.11%和91.76%；种间变异(LDMC除外)对结构性状的贡献率均高于化学性状；种内变异对LP的贡献率(23.66%)较种间变异高。(3)叶片性状之间多表现出显著相关关系，针叶树和阔叶树在PCA排序图中聚集于不同区域，叶经济型谱在柯-青冈群落中具有适用性。不同树种通过叶片结构、化学性状之间的权衡策略来适应环境变化，从而实现群落物种共存。结果可为理解森林群落物种的环境适应策略、预测群落动态变化和制定植被恢复措施提供科学依据。