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.     

海南岛霸王岭热带云雾林木本植物功能性状的分异规律

研究植物功能性状的分异,有助于理解植物适应环境的方式和策略,也能为预测物种分布和环境变化提供依据。以海南霸王岭热带云雾林为对象,建立21个20 m×20 m固定样方,划分为336个5 m×5 m小样方;测定胸径在5cm以上所有乔灌木植物个体的功能性状(叶面积LA;叶干重LDW;比叶重LMA;叶绿素含量Chl;叶厚度LTh;木材密度WD)和土壤养分含量,通过方差分解分析植物功能性状在个体、种内、种间、群落水平的分异大小,探究土壤养分对功能性状分异的影响。结果表明,LA、LDW、LMA、CHl、LTh、WD在个体、种内、种间、群落水平的解释方差范围分别为0.06—0.47、0.09—0.35、0.35—0.72、0—0.07,在个体、种内、种间、群落层次上,种间水平的功能性状分异最大,而群落水平的分异最小。逐步回归分析表明,不同尺度的功能性状变化与土壤有机质、氮和磷含量都有密切关系。     

Relative effects of phylogeny,biological characters and environments on leaf traits in shrub biomes across central Inner Mongolia,China

Aims Understanding the drivers for leaf traits is critical to improving our predictions on ecosystems' responses to global changes. Geographic patterns of leaf traits are shaped by phylogenetic, biological and environmental factors simultaneously. However, till now few studies have examined how these factors influenced leaf traits together, and how their effects differed at the within- and among-site levels.Methods We sampled leaf traits from a 1100 km shrub-biome transect across central Inner-Mongolia, including leaf mass per area (LMA), mass-based photosynthetic rate, nitrogen (N) and phosphorus (P) concentrations. We examined the effects of phylogenetic, biological (height and growth rate) and environmental (climate and soil) factors on leaf traits with mixed-model analyses of variance. Variation partitioning method was used to separate the joint and independent effects of these three types of factors.Important findings (i) Climate and soil fertility (total or available nutrient concentrations) together explained 11.4–41.4% of among-site variations, with remarkable difference among traits. (ii) Height and height growth rate together explained 0.4–31.9% of trait variations (mostly among-site variations). Our results could only weakly support the ability of leaf traits as predictors for whole-plant growth. (iii) LMA was negatively related to height, which was consistent with the resource-use strategy hypothesis but inconsistent with the hypotheses proposed for coexisting trees, suggesting that the LMA–height relationship is shaped by rather different mechanisms between the within- and among-communities levels. (iv) The variation partitioning analysis showed that, the relationships between leaf traits and biological characters largely reflected the differences in both leaf traits and biological characters among species that occupying different sites. The relative importance of phylogenetic, biological and environmental factors differed remarkably among leaf traits, between the within- and among-communities levels, and between different biomes. (v) Our results strongly suggest the necessity of examining the three types of factors simultaneously, and at both the within- and among-communities levels, for a better understanding of the drivers for leaf traits patterns.     

鼎湖山南亚热带常绿阔叶林叶功能性状沿群落垂直层次的种内变异

探究功能性状沿着环境梯度如何变化一直以来是基于性状的群落生态学的核心问题之一。尽管功能性状存在种内和种间变异, 但种内变异沿环境梯度如何变化仍有待探究。本文以鼎湖山南亚热带常绿阔叶林1.44 ha塔吊样地内16个树种的2,820个个体为研究对象, 探究4种叶功能性状(比叶面积、叶干物质含量、叶厚度和叶面积)沿群落垂直层次的种内变异。首先, 利用随机效应线性模型量化塔吊样地内的种内变异和种间变异; 其次, 利用Kmeans函数将森林的垂直层次划分为灌木层、亚冠层和林冠层, 并通过构建回归模型探究叶功能性状在群落垂直层次中的种内变异格局。最后, 应用混合线性模型和单因素方差分析的方法探究叶功能性状沿垂直层次的种内变异是否具有物种依赖性。结果表明: 在局域群落中, 并非所有叶功能性状的种内变异都低于种间变异; 叶功能性状在不同垂直层次的种内变异格局存在显著差异, 且种内变异与垂直范围呈正相关; 叶功能性状的种内变异具有较强的物种依赖性, 因此树种差异相对于小环境解释了更多的性状变异; 此外, 不同叶功能性状的种内变异沿垂直层次的变化趋势并不一致。本研究发现种内变异对于物种共存具有重要作用。     

Cross-species patterns in the coordination between leaf and stem traits, and their implications for plant hydraulics

Through identifying and understanding ecologically important dimensions of plant trait variation we gain insight into why particular trait combinations are favoured and into the implications of trait differences among species. Here, we describe relationships among several poorly understood leaf and stem traits across species from several Australian vegetation types. Species with lower wood density (WD) consistently deployed more leaf area per unit shoot mass (LA/SM), as did the larger-leaved species within forested sites. Higher LA/SM is likely to lead to faster growth rates, implying a previously unrecognized implication to interspecific variation in leaf size and WD. Leaf : sapwood area ratio is one of several important traits contributing to a plant's water-use strategy, yet, we still only poorly understand how plants vary in the extent to which hydraulic properties and traits such as leaf size, WD and LM/SM are coordinated, and what the implications of this variation may be.     

Intraspecific Trait Variation Driven by Plasticity and Ontogeny in Hypochaeris radicata

The importance of intraspecific variation in plant functional traits for structuring communities and driving ecosystem processes is increasingly recognized, but mechanisms governing this variation are less studied. Variation could be due to adaptation to local conditions, plasticity in observed traits, or ontogeny. We investigated 1) whether abiotic stress caused individuals, maternal lines, and populations to exhibit trait convergence, 2) whether trait variation was primarily due to ecotypic differences or trait plasticity, and 3) whether traits varied with ontogeny. We sampled three populations of Hypochaeris radicata that differed significantly in rosette diameter and specific leaf area (SLA). We grew nine maternal lines from each population (27 lines total) under three greenhouse conditions: ambient conditions (control), 50% drought, or 80% shade. Plant diameter and relative chlorophyll content were measured throughout the experiment, and leaf shape, root∶shoot ratio, and SLA were measured after five weeks. We used hierarchical mixed-models and variance component analysis to quantify differences in treatment effects and the contributions of population of origin and maternal line to observed variation. Observed variation in plant traits was driven primarily by plasticity. Shade significantly influenced all measured traits. Plant diameter was the only trait that had a sizable proportion of trait variation (30%) explained by population of origin. There were significant ontogenetic differences for both plant diameter and relative chlorophyll content. When subjected to abiotic stress in the form of light or water limitation, Hypochaeris radicata exhibited significant trait variability. This variation was due primarily to trait plasticity, rather than to adaptation to local conditions, and also differed with ontogeny.     

Plant phenology,leaf traits and leaf litterfall of contrasting life forms in the arid Patagonian Monte,Argentina

Question: Do coexisting plant life forms differ in overall phenology, leaf traits and patterns of leaf litterfall? Location: Patagonian Monte, Chubut Province, Argentina. Methods: We assessed phenology, traits of green and senesced leaves and the pattern of leaf litterfall in 12 species of coexisting life forms (perennial grasses, deciduous shrubs, evergreen shrubs). Results: We did not identify differences in phenology, leaf traits and patterns of leaf litterfall among life forms but these attributes contrasted among species. Independent of the life form, the maintenance of green leaves or vegetative growth during the dry season was mostly associated with leaves with high leaf mass per area (LMA) and high concentration of secondary compounds. Low LMA species produced low litterfall mass with low concentration of secondary compounds, and high N concentration. High LMA species produced the largest mass of leaf litterfall. Accordingly, species were distributed along two main dimensions of ecological variation, the dimension secondary compounds in leaves ‐ length and timing of the vegetative growth period (SC ‐ VGP) and the dimension leaf mass per area ‐ leaf litterfall mass (LMA ‐ LLM). Conclusions: Phenology, leaf traits and leaf litterfall varied among species and overlapped among life forms. The two dimensions of ecological variation among species (SC ‐ VGP, LMA ‐ LLM) represent distinct combinations of plant traits or strategies related to resource acquisition and drought tolerance which are reflected in the patterns of leaf litterfall.     

The interplay among intraspecific leaf trait variation,niche breadth and species abundance along light and soil nutrient gradients

It is assumed that widespread, generalist species have high phenotypic variation, but we know little about how intraspecific trait variation (ITV) relates to species abundance and niche breadth. In the temperate rainforest of southern Chile, we hypothesized that species with wide niche breadth would exhibit 1) high among‐plot ITV, 2) a strong relationship between trait values and the environment, and 3) a close fit between traits and local environment trait optima. We measured leaf functional traits (leaf area, LMA, leaf N and P concentrations) of saplings in woody species, and compared the relative abundance of each species with its niche breadth, measured as the range of light, soil N and P availability. We used the slope of the linear regression of species’ trait–environment relationships to assess the strength and direction of these relationships, and measured the degree to which species’ trait values track the environmental optimum across plots. In some cases, species having wide niche breadth had high ITV in leaf N and also matched traits (LMA and leaf P) to local optima along the light gradient; they also had high ITV in general and matched leaf P to local optima along the soil P gradient. The relationship between species with wide niche breadth and the strength of intraspecific trait–environment relationships was generally weak and varied depending on the niche dimension and trait in question. Species varied considerably in the strength of trait–environment relationships and total magnitude of ITV, and this variation was not generally strongly related to species abundances or niche breadth patterns. In conclusion, trait variation at the community level is not driven by a few abundant, widely distributed species, but depends on the aggregate trait responses of both abundant and rare species. This makes it difficult to scale individual species trait responses up to the community level.     

The acquisitive–conservative axis of leaf trait variation emerges even in homogeneous environments

Background and AimsThe acquisitive–conservative axis of plant ecological strategies results in a pattern of leaf trait covariation that captures the balance between leaf construction costs and plant growth potential. Studies evaluating trait covariation within species are scarcer, and have mostly dealt with variation in response to environmental gradients. Little work has been published on intraspecific patterns of leaf trait covariation in the absence of strong environmental variation.MethodsWe analysed covariation of four leaf functional traits [specific leaf area (SLA) leaf dry matter content (LDMC), force to tear (F_t) and leaf nitrogen content (N_m)] in six Poaceae and four Fabaceae species common in the dry Chaco forest of Central Argentina, growing in the field and in a common garden. We compared intraspecific covariation patterns (slopes, correlation and effect size) of leaf functional traits with global interspecific covariation patterns. Additionally, we checked for possible climatic and edaphic factors that could affect the intraspecific covariation pattern.Key ResultsWe found negative correlations for the LDMC–SLA, F_t–SLA, LDMC–N_m and F_t–N_m trait pairs. This intraspecific covariation pattern found both in the field and in the common garden and not explained by climatic or edaphic variation in the field follows the expected acquisitive–conservative axis. At the same time, we found quantitative differences in slopes among different species, and between these intraspecific patterns and the interspecific ones. Many of these differences seem to be idiosyncratic, but some appear consistent among species (e.g. all the intraspecific LDMC–SLA and LDMC–N_m slopes tend to be shallower than the global pattern).ConclusionsOur study indicates that the acquisitive–conservative leaf functional trait covariation pattern occurs at the intraspecific level even in the absence of relevant environmental variation in the field. This suggests a high degree of variation–covariation in leaf functional traits not driven by environmental variables.     

Phenotypic plasticity and precipitation response in Sonoran Desert winter annuals

Temporal environmental variation has profound influences on population dynamics and community structure. Examination of functional traits that influence resource uptake and allocation can illuminate how co-occurring species translate environmental variation into different demographic outcomes, yet few studies have considered interspecific differences in trait plasticity. We experimentally manipulated soil moisture to test the hypothesis that differences in morphological plasticity contribute to species differences in demographic response to unpredictable precipitation in Sonoran Desert winter annual plants. We compared plasticity of leaf traits and biomass allocation between Pectocarya recurvata (Boraginaceae) and Stylocline micropoides (Asteraceae), co-occurring species that differ in long-term demographic patterns. The species with highly variable population dynamics, Stylocline, had striking increases in leaf area and root biomass in response to an experimental increase in soil moisture. In contrast, the species with buffered long-term population dynamics, Pectocarya, did not differ in leaf morphology or biomass allocation between soil moisture treatments. Regardless of water treatment, Pectocarya had earlier reproductive phenology and greater fecundity than Stylocline, suggesting that differences in the timing of the phenological transitions from vegetative to reproductive growth may affect species' responses to precipitation pulses. Combining long-term observations with experimental manipulations provides a window into the functional underpinnings and demographic consequences of trait plasticity.     

Intraspecific Functional Trait Variation in a Tree Species (Lithocarpus dealbatus) along Latitude

We quantied intraspecic variation and covariation of leaf mass per area (LMA), leaf dry matter concentration (LD), leaf frost sensitivity (LFS) and Fv/Fm of leaves of 8 Lithocarpus dealbatus populations across the geographical distribution from north to south to determine the magnitude and whether it is related to environmental conditions, latitude and mean annual temperature. The results showed that the total variation (coefcient of variation) of LMA, LD, LFS and Fv/Fm were 160%, 177%, 211% and 401% respectively. The total intraspecic variation was contributed by the difference among populations, individuals and leaves. The difference among populations accounted for the largest total variation in LMA, LD and Fv/Fm, whereas the difference among leaves accounted for the largest total variation in LFS. On population level, LMA was significantly positive related to the latitude and Fv/Fm was significantly negative, but LD and LFS were not related to the latitude. LMA decreased while Fv/Fm increased significantly with the increase of mean annual temperature. LD was a downward quadratic variation, and LFS was upward with the increase of mean annual temperature. The principal component analysis of four functional traits showed that no population was located nearer to the origin of the first and second principal component, and populations at the edge of distribution area located at both sides of the first principal component axis. The results suggested that the environmental variation in the distribution could cause intraspecic variation of functional traits. There is no population could represent a species in functional traits. When an average trait value for species is considered and trait comparisons are done among species, intraspecific variation of traits could not be ignored.     

Shifts and plasticity of plant leaf mass per area and leaf size among slope aspects in a subalpine meadow

The composition of vegetation on a slope frequently changes substantially owing to the different micro‐environments of various slope aspects. To understand how the slope aspect affects the vegetation changes, we examined the variations in leaf mass per area (LMA) and leaf size (LS) within and among populations for 66 species from 14 plots with a variety of slope aspects in a subalpine meadow. LMA is a leaf economic trait that is tightly correlated with plant physiological traits, while the LS shows a tight correlation with leaf temperature, indicating the strategy of plants to self‐adjust in different thermal and hydraulic conditions. In this study, we compared the two leaf traits between slope aspects and between functional types and explored their correlation with soil variables and heat load. Our results showed that high‐LMA, small‐leaved species were favored in south‐facing slopes, while the reverse was true in north‐facing areas. In detail, small dense‐leaved graminoids dominated the south slopes, while large thin‐leaved forbs dominated the north slopes. Soil moisture and the availability of soil P were the two most important soil factors that related to both LMA and LS, and heat load also contributed substantially. Moreover, we disentangled the relative importance of intraspecific trait variation and species turnover in the trait variation among plots and found that the intraspecific variation contributed 98% and 56% to LMA and LS variation among communities, respectively, implying a large contribution of intraspecific trait plasticity. These results indicate that LMA and LS are two essential leaf traits that affect the adaptation or acclimation of plants underlying the vegetation composition changes in different slope aspects in the subalpine meadow.     

Leaf trait-environment relationships in a subtropical broadleaved forest in South-East China

Although trait analyses have become more important in community ecology, trait-environment correlations have rarely been studied along successional gradients. We asked which environmental variables had the strongest impact on intraspecific and interspecific trait variation in the community and which traits were most responsive to the environment. We established a series of plots in a secondary forest in the Chinese subtropics, stratified by successional stages that were defined by the time elapsed since the last logging activities. On a total of 27 plots all woody plants were recorded and a set of individuals of every species was analysed for leaf traits, resulting in a trait matrix of 26 leaf traits for 122 species. A Fourth Corner Analysis revealed that the mean values of many leaf traits were tightly related to the successional gradient. Most shifts in traits followed the leaf economics spectrum with decreasing specific leaf area and leaf nutrient contents with successional time. Beside succession, few additional environmental variables resulted in significant trait relationships, such as soil moisture and soil C and N content as well as topographical variables. Not all traits were related to the leaf economics spectrum, and thus, to the successional gradient, such as stomata size and density. By comparing different permutation models in the Fourth Corner Analysis, we found that the trait-environment link was based more on the association of species with the environment than of the communities with species traits. The strong species-environment association was brought about by a clear gradient in species composition along the succession series, while communities were not well differentiated in mean trait composition. In contrast, intraspecific trait variation did not show close environmental relationships. The study confirmed the role of environmental trait filtering in subtropical forests, with traits associated with the leaf economics spectrum being the most responsive ones.     

Examining variation in the leaf mass per area of dominant species across two contrasting tropical gradients in light of community assembly

Understanding variation in key functional traits across gradients in high diversity systems and the ecology of community changes along gradients in these systems is crucial in light of conservation and climate change. We examined inter‐ and intraspecific variation in leaf mass per area (LMA) of sun and shade leaves along a 3330‐m elevation gradient in Peru, and in sun leaves across a forest–savanna vegetation gradient in Brazil. We also compared LMA variance ratios (T‐statistics metrics) to null models to explore internal (i.e., abiotic) and environmental filtering on community structure along the gradients. Community‐weighted LMA increased with decreasing forest cover in Brazil, likely due to increased light availability and water stress, and increased with elevation in Peru, consistent with the leaf economic spectrum strategy expected in colder, less productive environments. A very high species turnover was observed along both environmental gradients, and consequently, the first source of variation in LMA was species turnover. Variation in LMA at the genus or family levels was greater in Peru than in Brazil. Using dominant trees to examine possible filters on community assembly, we found that in Brazil, internal filtering was strongest in the forest, while environmental filtering was observed in the dry savanna. In Peru, internal filtering was observed along 80% of the gradient, perhaps due to variation in taxa or interspecific competition. Environmental filtering was observed at cloud zone edges and in lowlands, possibly due to water and nutrient availability, respectively. These results related to variation in LMA indicate that biodiversity in species rich tropical assemblages may be structured by differential niche‐based processes. In the future, specific mechanisms generating these patterns of variation in leaf functional traits across tropical environmental gradients should be explored.     

Contrasting patterns of trait‐based community assembly in lianas and trees from temperate Australia

Trait variation in plant communities is thought to be constrained by two opposing community assembly processes operating at discrete spatial scales: habitat filtering and limiting similarity between coexisting species. Filtering processes cause convergence in ecological strategy as species are excluded from unsuitable sites, whilst limiting similarity leads to the divergence of trait values between co‐occurring species in order to alleviate competition for finite resources. Levels of alpha (within‐site) and beta (among‐site) trait variation can be indicative of the strength of these community assembly processes. We used trait‐gradient analysis to explicitly compare evidence of community assembly patterns in lianas (woody vines) and trees. These two growth forms exhibit striking differences in carbon capture and regeneration strategies, yet trait‐based mechanisms that maintain their coexistence remain understudied. Using data for four functional traits – leaf mass per area, leaf nitrogen content (N_mass), leaf area and seed mass – we partitioned interspecific trait variation in lianas and trees into alpha and beta components. Our three key findings were: 1) lianas and trees exhibit divergent patterns of trait‐based habitat filtering, due to differences in the relationship between leaf size and the other three traits examined (LMA, N_mass and seed mass), 2) on average, liana species possess smaller seeds, lower LMA and higher N_mass than do trees, but there was no clear difference in leaf area between the two growth forms, and 3) soil fertility was correlated with trait variation (leaf area, seed mass) at the site‐level in trees, but not in lianas. These results provide evidence that dominant growth forms can be filtered into the same habitat on the basis of different combinations of traits. Our findings have important implications for community assembly and co‐existence theory and for more pragmatic matters such as using trait‐based principles to inform community restoration.     

不同水盐环境下荒漠植物群落抗逆性化学性状的种间、种内变异

叶片是植物获取资源的重要器官,研究荒漠植物抗逆性化学性状的种间、种内变异对环境变化的响应有助于揭示植物对极端环境的适应机制。以艾比湖自然荒漠植物群落为研究对象,通过野外调查与实验分析,解析不同土壤水盐环境下群落水平抗逆性化学性状（钾K;钙Ca;钠Na;镁Mg）的差异及其种间、种内变异特征,利用冗余分析、相关性分析,明析群落水平性状种间、种内变异与土壤环境因子间关系及其在不同水盐环境间的变化规律。结果表明：（1）高水盐环境下土壤pH及Ca、Na含量均显著高于低水盐环境;低水盐环境下群落水平K、Na、Mg含量显著高于高水盐环境。（2）高水盐环境下群落抗逆性化学性状的种间变异（Ca除外,P<0.05）、种内变异均低于低水盐环境。（3）高水盐环境土壤因子与群落种间、种内变异相关性较高（|r|>0.3）,其中与叶片Ca、Na种间变异普遍为负相关,与Na种内变异多为较强的正相关;低水盐环境种间、种内变异与土壤因子相关性总体较低,其中土壤盐分、水分与叶片Mg的种间变异呈负相关,与Na种内变异呈正相关。综上所述,水盐环境对荒漠植物群落水平的抗逆性化学性状有显著影响,各性状的种间、种内变异与土壤因子间关系在高水盐环境中更为密切,本研究为掌握胁迫环境下植物的适应策略提供依据。     

Modulation of leaf economic traits and trait relationships by climate

Aim Our aim was to quantify climatic influences on key leaf traits and relationships at the global scale. This knowledge provides insight into how plants have adapted to different environmental pressures, and will lead to better calibration of future vegetation–climate models. Location The data set represents vegetation from 175 sites around the world. Methods For more than 2500 vascular plant species, we compiled data on leaf mass per area (LMA), leaf life span (LL), nitrogen concentration (N_mass) and photosynthetic capacity (A_mass). Site climate was described with several standard indices. Correlation and regression analyses were used for quantifying relationships between single leaf traits and climate. Standardized major axis (SMA) analyses were used for assessing the effect of climate on bivariate relationships between leaf traits. Principal components analysis (PCA) was used to summarize multidimensional trait variation. Results At hotter, drier and higher irradiance sites, (1) mean LMA and leaf N per area were higher; (2) average LL was shorter at a given LMA, or the increase in LL was less for a given increase in LMA (LL–LMA relationships became less positive); and (3) A_mass was lower at a given N_mass, or the increase in A_mass was less for a given increase in N_mass. Considering all traits simultaneously, 18% of variation along the principal multivariate trait axis was explained by climate. Main conclusions Trait‐shifts with climate were of sufficient magnitude to have major implications for plant dry mass and nutrient economics, and represent substantial selective pressures associated with adaptation to different climatic regimes.     

The leaf economics spectrum’s morning coffee: plant size-dependent changes in leaf traits and reproductive onset in a perennial tree crop

Background and AimsSize-dependent changes in plant traits are an important source of intraspecific trait variation. However, there are few studies that have tested if leaf trait co-variation and/or trade-offs follow a within-genotype leaf economics spectrum (LES) related to plant size and reproductive onset. To our knowledge, there are no studies on any plant species that have tested whether or not the shape of a within-genotype LES that describes how traits covary across whole plant sizes, is the same as the shape of a within-genotype LES that represents environmentally driven trait plasticity.MethodsWe quantified size-dependent variation in eight leaf traits in a single coffee genotype (Coffea arabica var. Caturra) in managed agroecosystems with different environmental conditions (light and fertilization treatments), and evaluated these patterns with respect to reproductive onset. We also evaluated if trait covariation along a within-genotype plant-size LES differed from a within-genotype environmental LES defined with trait data from coffee growing in different environmental conditions.Key ResultsLeaf economics traits related to resource acquisition – maximum photosynthetic rates (A) and mass-based leaf nitrogen (N) concentrations – declined linearly with plant size. Structural traits – leaf mass, leaf thickness, and leaf mass per unit area (LMA) – and leaf area increased with plant size beyond reproductive onset, then declined in larger plants. Three primary LES traits (mass-based A, leaf N and LMA) covaried across a within-genotype plant-size LES, with plants moving towards the ‘resource-conserving’ end of the LES as they grow larger; in coffee these patterns were nearly identical to a within-genotype environmental LES.ConclusionsOur results demonstrate that a plant-size LES exists within a single genotype. Our findings indicate that in managed agroecosystems where resource availability is high the role of reproductive onset in driving within-genotype trait variability, and the strength of covariation and trade-offs among LES traits, are less pronounced compared with plants in natural systems. The consistency in trait covariation in coffee along both plant-size and environmental LES axes indicates strong constraints on leaf form and function that exist within plant genotypes.     

Intraspecific trait variation of woody species reduced in a savanna community,southwest China

Plants deploy various ecological strategies in response to environmental heterogeneity. In many forest ecosystems, plants have been reported to have notable inter- and intra-specific trait variation, as well as clear phylogenetic signals, indicating that these species possess a degree of phenotypic plasticity to cope with habitat variation in the community. Savanna communities, however, grow in an open canopy structure and exhibit little species diversification, likely as a result of strong environmental stress. In this study, we hypothesized that the phylogenetic signals of savanna species would be weak, the intraspecific trait variation (ITV) would be low, and the contribution of intraspecific variation to total trait variance would be reduced, owing to low species richness, multiple stresses and relatively homogenous community structure. To test these hypotheses, we sampled dominant woody species in a dry-hot savanna in southwestern China, focusing on leaf traits related to adaptability of plants to harsh conditions (year-round intense radiation, low soil fertility and seasonal droughts). We found weak phylogenetic signals in leaf traits and low ITV (at both individual and canopy-layer levels). Intraspecific variation (including leaf-, layer- and individual-scales) contributed little to the total trait variance, whereas interspecific variation and variation in leaf phenology explained substantial variance. Our study suggests that intraspecific trait variation is reduced in savanna community. Furthermore, our findings indicate that classifying species by leaf phenology may help better understand how species coexist under similar habitats with strong stresses.     

Trait variation and functional diversity maintenance of understory herbaceous species coexisting along an elevational gradient in Yulong Mountain,Southwest China

Characterizing trait variation across different ecological scales in plant communities has been viewed as a way to gain insights into the mechanisms driving species coexistence. However, little is known about how changes in intraspecific and interspecific traits across sites influence species richness and community assembly, especially in understory herbaceous communities. Here we partitioned the variance of four functional traits (maximum height, leaf thickness, leaf area and specific leaf area) across four nested biological scales: individual, species, plot, and elevation to quantify the scale-dependent distributions of understory herbaceous trait variance. We also integrated the comparison of the trait variance ratios to null models to investigate the effects of different ecological processes on community assembly and functional diversity along a 1200-m elevational gradient in Yulong Mountain. We found interspecific trait variation was the main trait variation component for leaf traits, although intraspecific trait variation ranged from 10% to 28% of total variation. In particular, maximum height exhibited high plasticity, and intraspecific variation accounted for 44% of the total variation. Despite the fact that species composition varied across elevation and species richness decreased dramatically along the elevational gradient, there was little variance at our largest (elevation) scale in leaf traits and functional diversity remained constant along the elevational gradient, indicating that traits responded to smaller scale influences. External filtering was only observed at high elevations. However, strong internal filtering was detected along the entire elevational gradient in understory herbaceous communities, possibly due to competition. Our results provide evidence that species coexistence in understory herbaceous communities might be structured by differential niche-assembled processes. This approach--integrating different biological scales of trait variation--may provide a better understanding of the mechanisms involved in the structure of communities.