Plants of nutrient-poor, arid environments often have leaf traits that include small size, sclerophylly, long life span, low nutrient concentration, and low photosynthetic rate. Hence, the success of two large-leaved palmettos in peninsular Florida's seasonally xeric, nutrient-impoverished uplands seems anomalous, given that their leaves are orders of magnitude larger than the leaves of sympatric species. An examination of a 16-yr data set of leaf traits and leaf life spans across four vegetative associations differing in available light showed that Serenoa repens and Sabal etonia had low rates of leaf production coupled with long leaf life spans reaching 3.5 yr in heavily shaded plants. The adaptation of these palmettos to xeric, nutrient-poor habitats has generated dwarf statures, diminished leaf sizes and numbers, increased leaf life spans, and reduced rates of leaf production relative to other palms and congeners of more mesic sites. Leaf and petiole size, plant leaf canopy area, and leaf life span increased in both palmettos with decreasing available light, helping to compensate for reduced photosynthetic rates under shaded conditions and for the high leaf construction costs of the large, thick palmetto leaves. Large leaf size in these palmettos, likely due to phylogenetic conservatism, is compensated by other leaf traits (e.g., heavily cutinized epidermises, thick laminas) that increase survival in seasonally xeric, nutrient-impoverished environments.

Numerous studies have suggested that biodiversity reduces variability in ecosystem productivity through compensatory effects; that is, a species increases in its abundance in response to the reduction of another in a fluctuating environment. But this view has been challenged on several grounds. Because most studies have been based on artificially constructed grasslands with short duration, long-term studies of natural ecosystems are needed. On the basis of a 24-year study of the Inner Mongolia grassland, here we present three key findings. First, that January-July precipitation is the primary climatic factor causing fluctuations in community biomass production; second, that ecosystem stability (conversely related to variability in community biomass production) increases progressively along the hierarchy of organizational levels (that is, from species to functional group to whole community); and finally, that the community-level stability seems to arise from compensatory interactions among major components at both species and functional group levels. From a hierarchical perspective, our results corroborate some previous findings of compensatory effects. Undisturbed mature steppe ecosystems seem to culminate with high biodiversity, productivity and ecosystem stability concurrently. Because these relationships are correlational, further studies are necessary to verify the causation among these factors. Our study provides new insights for better management and restoration of the rapidly degrading Inner Mongolia grassland.

Drought is a critical factor in plant species distributions. Much research points to its relevance even in moist tropical regions. Recent studies have begun to elucidate mechanisms underlying the distributions of tropical tree species with respect to drought; however, how such desiccation tolerance mechanisms correspond with the coordination of hydraulic and photosynthetic traits in determining species distributions with respect to rainfall seasonality deserves attention. In the present study, we used a common garden approach to quantify inherent differences in wood anatomical and foliar physiological traits in 21 tropical tree species with either widespread (occupying both seasonal and aseasonal climates) or southern (restricted to aseasonal forests) distributions with respect to rainfall seasonality. Use of congeneric species pairs and phylogenetically independent contrast analyses allowed examination of this question in a phylogenetic framework. Widespread species opted for wood traits that provide biomechanical support and prevent xylem cavitation and showed associated reductions in canopy productivity and consequently growth rates compared with southern species. These data support the hypothesis that species having broader distributions with respect to climatic variability will be characterized by traits conducive to abiotic stress tolerance. This study highlights the importance of the well-established performance vs. stress tolerance trade-off as a contributor to species distributions at larger scales.

BACKGROUND: Strong patterns of habitat association are frequent among tropical forest trees and contribute to the maintenance of biodiversity. The relation of edaphic differentiation to tradeoffs among leaf functional traits is less clear, but may provide insights into mechanisms of habitat partitioning in these species rich assemblages. METHODOLOGY/PRINCIPAL FINDINGS: We quantify the leaf economics spectrum (LES) for 16 tree species within a Bornean forest characterized by highly pronounced habitat specialization. Our findings suggest that the primary axis of trait variation in light-limited, lowland tropical forests was identical to the LES and corresponds with the shade tolerance continuum. There was no separation with respect to edaphic variation along this primary axis of trait variation. However, a second orthogonal axis determined largely by foliar P concentrations resulted in a near-perfect separation of species occupying distinct soil types within the forest. CONCLUSIONS/SIGNIFICANCE: We suggest that this second axis of leaf trait variation represents a

Cross-species analyses of plant functional traits have shed light on factors contributing to differences in performance and distribution, but to date most studies have focused on either leaves or stems. We extend these tissue-specific analyses of functional strategy towards a whole-plant approach by integrating data on functional traits for 13 448 leaves and wood tissues from 4672 trees representing 668 species of Neotropical trees. Strong correlations amongst traits previously defined as the leaf economics spectrum reflect a tradeoff between investments in productive leaves with rapid turnover vs. costly physical leaf structure with a long revenue stream. A second axis of variation, the 'stem economics spectrum', defines a similar tradeoff at the stem level: dense wood vs. high wood water content and thick bark. Most importantly, these two axes are orthogonal, suggesting that tradeoffs operate independently at the leaf and at the stem levels. By simplifying the multivariate ecological strategies of tropical trees into positions along these two spectra, our results provide a basis to improve global vegetation models predicting responses of tropical forests to global change.

The leaf economics spectrum describes biome-invariant scaling functions for leaf functional traits that relate to global primary productivity and nutrient cycling. Here, we develop a comprehensive framework for the origin of this leaf economics spectrum based on venation-mediated economic strategies. We define a standardized set of traits - density, distance and loopiness - that provides a common language for the study of venation. We develop a novel quantitative model that uses these venation traits to model leaf-level physiology, and show that selection to optimize the venation network predicts the mean global trait-trait scaling relationships across 2548 species. Furthermore, using empirical venation data for 25 plant species, we test our model by predicting four key leaf functional traits related to leaf economics: net carbon assimilation rate, life span, leaf mass per area ratio and nitrogen content. Together, these results indicate that selection on venation geometry is a fundamental basis for understanding the diversity of leaf form and function, and the carbon balance of leaves. The model and associated predictions have broad implications for integrating venation network geometry with pattern and process in ecophysiology, ecology and palaeobotany.

Wood performs several essential functions in plants, including mechanically supporting aboveground tissue, storing water and other resources, and transporting sap. Woody tissues are likely to face physiological, structural and defensive trade-offs. How a plant optimizes among these competing functions can have major ecological implications, which have been under-appreciated by ecologists compared to the focus they have given to leaf function. To draw together our current understanding of wood function, we identify and collate data on the major wood functional traits, including the largest wood density database to date (8412 taxa), mechanical strength measures and anatomical features, as well as clade-specific features such as secondary chemistry. We then show how wood traits are related to one another, highlighting functional trade-offs, and to ecological and demographic plant features (growth form, growth rate, latitude, ecological setting). We suggest that, similar to the manifold that tree species leaf traits cluster around the 'leaf economics spectrum', a similar 'wood economics spectrum' may be defined. We then discuss the biogeography, evolution and biogeochemistry of the spectrum, and conclude by pointing out the major gaps in our current knowledge of wood functional traits.

As ecological data are usually analysed at a scale different from the one at which the process of interest operates, interpretations can be confusing and controversial. For example, hypothesised differences between species do not operate at the species level, but concern individuals responding to environmental variation, including competition with neighbours. Aggregated data from many individuals subject to spatio-temporal variation are used to produce species-level averages, which marginalise away the relevant (process-level) scale. Paradoxically, the higher the dimensionality, the more ways there are to differ, yet the more species appear the same. The aggregate becomes increasingly irrelevant and misleading. Standard analyses can make species look the same, reverse species rankings along niche axes, make the surprising prediction that a species decreases in abundance when a competitor is removed from a model, or simply preclude parameter estimation. Aggregation explains why niche differences hidden at the species level become apparent upon disaggregation to the individual level, why models suggest that individual-level variation has a minor impact on diversity when disaggregation shows it to be important, and why literature-based synthesis can be unfruitful. We show how to identify when aggregation is the problem, where it has caused controversy, and propose three ways to address it.

Worldwide decomposition rates depend both on climate and the legacy of plant functional traits as litter quality. To quantify the degree to which functional differentiation among species affects their litter decomposition rates, we brought together leaf trait and litter mass loss data for 818 species from 66 decomposition experiments on six continents. We show that: (i) the magnitude of species-driven differences is much larger than previously thought and greater than climate-driven variation; (ii) the decomposability of a species' litter is consistently correlated with that species' ecological strategy within different ecosystems globally, representing a new connection between whole plant carbon strategy and biogeochemical cycling. This connection between plant strategies and decomposability is crucial for both understanding vegetation-soil feedbacks, and for improving forecasts of the global carbon cycle.

Despite the importance of leaf traits that protect against critically high leaf temperatures, relationships among such traits have not been investigated. Further, while some leaf trait relationships are well documented across biomes, little is known about such associations within a biome. This study investigated relationships between nine leaf traits that protect leaves against excessively high temperatures in 95 Australian arid zone species. Seven morphological traits were measured: leaf area, length, width, thickness, leaf mass per area, water content, and an inverse measure of pendulousness. Two spectral properties were measured: reflectance of visible and near-infrared radiation. Three key findings emerged: (1) leaf pendulousness increased with leaf size and leaf mass per area, the former relationship suggesting that pendulousness affords thermal protection when leaves are large; (2) leaf mass per area increased with thickness and decreased with water content, indicating alternative means for protection through increasing thermal mass; (3) spectral reflectance increased with leaf mass per area and thickness and decreased with water content. The consistent co-variation of thermal protective traits with leaf mass per area, a trait not usually associated with thermal protection, suggests that these traits fall along the leaf economics spectrum, with leaf longevity increasing through protection not only against structural damage but also against heat stress.

BACKGROUND AND AIMS: Although plant functional traits (PFTs) appear to be important indicators of species' responses to land use changes, there is no clear understanding of how the variations in traits and their plasticity determine variations in species performance. This study investigated the role of functional shoot traits and their plasticity for variation in above-ground net primary productivity (ANPP) due to changes in N supply and in cutting frequency for 13 native perennial C(3) grass species. METHODS: Monocultures of the grass species were grown in a fully factorial block design combining plant species, cutting frequency and N supply as factors. KEY RESULTS: Four major trait associations were obtained by reducing the dimensions of 14 PFTs with a principal component analysis (PCA).Variations in species' productivity in response to an increase in cutting frequency was mainly explained by traits linked to the first PCA axis, opposing high plant stature from lower shoot cellulose and lignin contents and high leaf N content. Variation in species productivity in response to change in N supply was mainly explained by a set of predictor variables combining traits (average flowering date) and a trait's plasticity (tiller density per unit land area and leaf dry matter content, i.e. mg dry matter g fresh mass(-1)). These traits involved are linked to the second PCA axis ('nutrient acquisition-conservation'), which opposes distinct strategies based on response to nutrient supply. CONCLUSIONS: Variations in ANPP of species in response to an increase in cutting frequency and a decrease in N supply are controlled by a group of traits, rather than by one individual trait. Incorporating plasticity of the individual traits into these trait combinations was the key to explaining species' productivity responses, accounting for up to 89 % of the total variability in response to the changes in N supply.

The worldwide leaf economic spectrum (WLES) is a strikingly consistent pattern of correlations among leaf traits. Although the WLES effectively summarizes variation in plant ecological strategies, little is known about its evolution. We reviewed estimates of natural selection and genetic variation for leaf traits to test whether the evolution of the WLES was limited by selection against unfit trait combinations or by genetic constraints. There was significant selection for leaf traits on both ends of the WLES spectrum, as well as significant genetic variation for these traits. In addition, genetic correlations between WLES traits were variable in strength and direction. These data suggest that genetic constraints have had a smaller role than selection in the evolution of the WLES.

Understanding the mechanisms of trait selection at the scale of plant communities is a crucial step toward predicting community assembly. Although it is commonly assumed that disturbance and resource availability constrain separate suites of traits, representing the regenerative and established phases, respectively, a quantification and test of this accepted hypothesis is still lacking due to limitations of traditional statistical techniques. In this paper we quantify, using structural equation modeling (SEM), the relative contributions of disturbance and resource availability to the selection of suites of traits at the community scale. Our model specifies and reflects previously obtained ecological insights, taking disturbance and nutrient availability as central drivers affecting leaf, allometric, seed, and phenology traits in 156 (semi-) natural plant communities throughout The Netherlands. The common hypothesis positing that disturbance and resource availability each affect a set of mutually independent traits was not consistent with the data. Instead, our final model shows that most traits are strongly affected by both drivers. In addition, trait-trait constraints are more important in community assembly than environmental drivers in half of the cases. Both aspects of trait selection are crucial for correctly predicting ecosystem processes and community assembly, and they provide new insights into hitherto underappreciated ecological interactions.

Linking functional traits to plant growth is critical for scaling attributes of organisms to the dynamics of ecosystems and for understanding how selection shapes integrated botanical phenotypes. However, a general mechanistic theory showing how traits specifically influence carbon and biomass flux within and across plants is needed. Building on foundational work on relative growth rate, recent work on functional trait spectra, and metabolic scaling theory, here we derive a generalized trait-based model of plant growth. In agreement with a wide variety of empirical data, our model uniquely predicts how key functional traits interact to regulate variation in relative growth rate, the allometric growth normalizations for both angiosperms and gymnosperms, and the quantitative form of several functional trait spectra relationships. The model also provides a general quantitative framework to incorporate additional leaf-level trait scaling relationships and hence to unite functional trait spectra with theories of relative growth rate, and metabolic scaling. We apply the model to calculate carbon use efficiency. This often ignored trait, which may influence variation in relative growth rate, appears to vary directionally across geographic gradients. Together, our results show how both quantitative plant traits and the geometry of vascular transport networks can be merged into a common scaling theory. Our model provides a framework for predicting not only how traits covary within an integrated allometric phenotype but also how trait variation mechanistically influences plant growth and carbon flux within and across diverse ecosystems.

Aims As a key element in plant tissue, nitrogen plays an important role in the growth and development of plants. Our objective is to determine (1) how both leaf nitrogen and its allocation between photosynthetic and non-photosynthetic systems have responded to an altitudinal gradient and (2) what role their response has played in the adaptation of Rumex dentatus to its changed environment along the altitudinal gradient.Methods We measured foliar parameters of photosynthesis, diffusional conductance to CO2, stable carbon isotope ratio (δ13C), nitrogen content and specific leaf area (SLA) of the forb R. dentatus in four sites with different altitudes (2 350, 2 700, 3 150 and 3 530 m) in the Wolong Reserve. One-way ANOVA was used to find the differences for all parameters among R. dentatus plants from different altitudes, and standardized major axis (SMA) was used to determine the relationships among some main parameters.Important findings Leaf nitrogen content per area (Narea) increased as maximum photosynthetic capacity (Amax) increased with altitude in R. dentatus. Increased diffusional conductance also had a positive effect on increased photosynthetic capacity with altitude. These may be the result of adaptation of plants to a shortened leaf lifespan caused by low temperature at high altitude. Along with the altitudinal gradient, nitrogen and diffusional conductance of R. dentatus have an indirect effect on foliar δ13C through acting on the ratio of chloroplast partial pressure of CO2 to ambient CO2 partial pressure (Pc/Pa). Compared with diffusional conductance, nitrogen (or carboxylation capacity based on nitrogen) played a more important role in the process, in order to increase foliar δ13C with altitude. Rumex dentatus allocated more nitrogen to build defensive structural tissue with increased altitude. This is why SLA and photosynthetic nitrogen use efficiency (PNUE) decreased with altitude. In the photosynthetic system, more nitrogen was allocated to light-harvesting components in order that enhanced light resource was used preferably by R. dentatus, and then photosynthetic capacity was increased with altitude. Nitrogen and its allocation among systems (especially between photosynthetic and non-photosynthetic systems) are the keys to the adaptation and the response of R. dentatus to the gradient in altitude.]]>Aims As a key element in plant tissue, nitrogen plays an important role in the growth and development of plants. Our objective is to determine (1) how both leaf nitrogen and its allocation between photosynthetic and non-photosynthetic systems have responded to an altitudinal gradient and (2) what role their response has played in the adaptation of Rumex dentatus to its changed environment along the altitudinal gradient.Methods We measured foliar parameters of photosynthesis, diffusional conductance to CO2, stable carbon isotope ratio (δ13C), nitrogen content and specific leaf area (SLA) of the forb R. dentatus in four sites with different altitudes (2 350, 2 700, 3 150 and 3 530 m) in the Wolong Reserve. One-way ANOVA was used to find the differences for all parameters among R. dentatus plants from different altitudes, and standardized major axis (SMA) was used to determine the relationships among some main parameters.Important findings Leaf nitrogen content per area (Narea) increased as maximum photosynthetic capacity (Amax) increased with altitude in R. dentatus. Increased diffusional conductance also had a positive effect on increased photosynthetic capacity with altitude. These may be the result of adaptation of plants to a shortened leaf lifespan caused by low temperature at high altitude. Along with the altitudinal gradient, nitrogen and diffusional conductance of R. dentatus have an indirect effect on foliar δ13C through acting on the ratio of chloroplast partial pressure of CO2 to ambient CO2 partial pressure (Pc/Pa). Compared with diffusional conductance, nitrogen (or carboxylation capacity based on nitrogen) played a more important role in the process, in order to increase foliar δ13C with altitude. Rumex dentatus allocated more nitrogen to build defensive structural tissue with increased altitude. This is why SLA and photosynthetic nitrogen use efficiency (PNUE) decreased with altitude. In the photosynthetic system, more nitrogen was allocated to light-harvesting components in order that enhanced light resource was used preferably by R. dentatus, and then photosynthetic capacity was increased with altitude. Nitrogen and its allocation among systems (especially between photosynthetic and non-photosynthetic systems) are the keys to the adaptation and the response of R. dentatus to the gradient in altitude.]]>Aims As a key element in plant tissue, nitrogen plays an important role in the growth and development of plants. Our objective is to determine (1) how both leaf nitrogen and its allocation between photosynthetic and non-photosynthetic systems have responded to an altitudinal gradient and (2) what role their response has played in the adaptation of Rumex dentatus to its changed environment along the altitudinal gradient.Methods We measured foliar parameters of photosynthesis, diffusional conductance to CO2, stable carbon isotope ratio (δ13C), nitrogen content and specific leaf area (SLA) of the forb R. dentatus in four sites with different altitudes (2 350, 2 700, 3 150 and 3 530 m) in the Wolong Reserve. One-way ANOVA was used to find the differences for all parameters among R. dentatus plants from different altitudes, and standardized major axis (SMA) was used to determine the relationships among some main parameters.Important findings Leaf nitrogen content per area (Narea) increased as maximum photosynthetic capacity (Amax) increased with altitude in R. dentatus. Increased diffusional conductance also had a positive effect on increased photosynthetic capacity with altitude. These may be the result of adaptation of plants to a shortened leaf lifespan caused by low temperature at high altitude. Along with the altitudinal gradient, nitrogen and diffusional conductance of R. dentatus have an indirect effect on foliar δ13C through acting on the ratio of chloroplast partial pressure of CO2 to ambient CO2 partial pressure (Pc/Pa). Compared with diffusional conductance, nitrogen (or carboxylation capacity based on nitrogen) played a more important role in the process, in order to increase foliar δ13C with altitude. Rumex dentatus allocated more nitrogen to build defensive structural tissue with increased altitude. This is why SLA and photosynthetic nitrogen use efficiency (PNUE) decreased with altitude. In the photosynthetic system, more nitrogen was allocated to light-harvesting components in order that enhanced light resource was used preferably by R. dentatus, and then photosynthetic capacity was increased with altitude. Nitrogen and its allocation among systems (especially between photosynthetic and non-photosynthetic systems) are the keys to the adaptation and the response of R. dentatus to the gradient in altitude.]]>

Rumex dentatus)的4个分布地点(2 350、2 700、3 150和3 530 m), 对各研究地点的齿果酸模进行了叶片光合、扩散导度、叶片碳稳定同位素组成(δ13C)、氮素含量、光合氮利用效率(PNUE)、比叶面积(SLA))等参数的测量, 以期揭示该植物叶片氮素、氮素分配情况及其他生理生态参数随海拔的响应趋势, 进而明确氮素及其分配在齿果酸模响应和适应海拔梯度环境的生物学过程中的作用。结果表明: 随着海拔的升高, 齿果酸模的叶片单位面积氮含量(Narea)随之增加, 进而光合能力随之增加。随着海拔升高而增加的扩散导度也在一定程度上促进了这一趋势, 这可能是落叶草本植物对于高海拔低温所导致的叶寿命缩短的适应结果。沿着海拔梯度, 植物叶片氮素和扩散导度均通过羧化位点与外界CO2分压比(Pc/Pa)而间接影响叶片δ13C值, 且相比之下, 以氮素为基础的羧化能力对于Pc/Pa的作用更大些, 进而导致齿果酸模叶片δ13C随海拔增加; 随着海拔的升高, 齿果酸模叶片将更多的氮素用于防御性结构组织的建设, 这也是SLA和PNUE降低的主要原因; 在光合系统内部, 随着海拔的升高, 植物光合组织增加了用于捕光系统氮素的比例, 使得植物可以更好地利用随海拔升高而增强的光照资源, 进而促进了光合能力的增加。可见, 氮素及其在叶片各系统间(尤其是在光合系统与非光合系统间)的分配方式是齿果酸模适应和响应海拔梯度环境的关键。]]>Rumex dentatus)的4个分布地点(2 350、2 700、3 150和3 530 m), 对各研究地点的齿果酸模进行了叶片光合、扩散导度、叶片碳稳定同位素组成(δ13C)、氮素含量、光合氮利用效率(PNUE)、比叶面积(SLA))等参数的测量, 以期揭示该植物叶片氮素、氮素分配情况及其他生理生态参数随海拔的响应趋势, 进而明确氮素及其分配在齿果酸模响应和适应海拔梯度环境的生物学过程中的作用。结果表明: 随着海拔的升高, 齿果酸模的叶片单位面积氮含量(Narea)随之增加, 进而光合能力随之增加。随着海拔升高而增加的扩散导度也在一定程度上促进了这一趋势, 这可能是落叶草本植物对于高海拔低温所导致的叶寿命缩短的适应结果。沿着海拔梯度, 植物叶片氮素和扩散导度均通过羧化位点与外界CO2分压比(Pc/Pa)而间接影响叶片δ13C值, 且相比之下, 以氮素为基础的羧化能力对于Pc/Pa的作用更大些, 进而导致齿果酸模叶片δ13C随海拔增加; 随着海拔的升高, 齿果酸模叶片将更多的氮素用于防御性结构组织的建设, 这也是SLA和PNUE降低的主要原因; 在光合系统内部, 随着海拔的升高, 植物光合组织增加了用于捕光系统氮素的比例, 使得植物可以更好地利用随海拔升高而增强的光照资源, 进而促进了光合能力的增加。可见, 氮素及其在叶片各系统间(尤其是在光合系统与非光合系统间)的分配方式是齿果酸模适应和响应海拔梯度环境的关键。]]>Rumex dentatus)的4个分布地点(2 350、2 700、3 150和3 530 m), 对各研究地点的齿果酸模进行了叶片光合、扩散导度、叶片碳稳定同位素组成(δ13C)、氮素含量、光合氮利用效率(PNUE)、比叶面积(SLA))等参数的测量, 以期揭示该植物叶片氮素、氮素分配情况及其他生理生态参数随海拔的响应趋势, 进而明确氮素及其分配在齿果酸模响应和适应海拔梯度环境的生物学过程中的作用。结果表明: 随着海拔的升高, 齿果酸模的叶片单位面积氮含量(Narea)随之增加, 进而光合能力随之增加。随着海拔升高而增加的扩散导度也在一定程度上促进了这一趋势, 这可能是落叶草本植物对于高海拔低温所导致的叶寿命缩短的适应结果。沿着海拔梯度, 植物叶片氮素和扩散导度均通过羧化位点与外界CO2分压比(Pc/Pa)而间接影响叶片δ13C值, 且相比之下, 以氮素为基础的羧化能力对于Pc/Pa的作用更大些, 进而导致齿果酸模叶片δ13C随海拔增加; 随着海拔的升高, 齿果酸模叶片将更多的氮素用于防御性结构组织的建设, 这也是SLA和PNUE降低的主要原因; 在光合系统内部, 随着海拔的升高, 植物光合组织增加了用于捕光系统氮素的比例, 使得植物可以更好地利用随海拔升高而增强的光照资源, 进而促进了光合能力的增加。可见, 氮素及其在叶片各系统间(尤其是在光合系统与非光合系统间)的分配方式是齿果酸模适应和响应海拔梯度环境的关键。]]>

1. Trade-offs among functional traits reveal major plant strategies that can give insight into species distributions and ecosystem processes. However, current identification of plant strategies lacks the integration of root structural traits together with leaf and stem traits. 2. We examined correlations among 14 traits representing leaf, stem and woody root tissues. Traits were measured on 1084 individuals representing 758 Neotropical tree species, across 13 sites representative of the environmental variation encompassed by three widespread habitats (seasonally flooded, clay terra firme and white-sand forests) at opposite ends of Amazonia (French Guiana and Peru). 3. Woody root traits were closely aligned with stem traits, but not with leaf traits. Altogether leaf, stem and woody root traits delineated two orthogonal axes of functional trade-offs: a first axis defined by leaf traits, corresponding to a leaf economics spectrum, and a second axis defined by covarying stem and woody root traits, corresponding to a wood economics spectrum. These axes remained consistent when accounting for species evolutionary history with phylogenetically independent contrasts. 4. Despite the strong species turnover across sites, the covariation among root and stem structural traits as well as their orthogonality to leaf traits were strongly consistent across habitats and regions. 5. We conclude that root structural traits mirrored stem traits rather than leaf traits in Neotropical trees. Leaf and wood traits define an integrated whole-plant strategy in lowland South American forests that may contribute to a more complete understanding of plant responses to global changes in both correlative and modelling approaches. We suggest further meta-analyses in expanded environmental and geographic zones to determine the generality of this pattern.

Questions: (1) How do community-weighted mean (CWM) trait values of 23 functional traits measured on 34 plant species vary along a gradient of aridity under grazed and ungrazed conditions in an arid steppe? (2) How does variation in our CWMtrait values differ fromthose ofmoremesic grasslands? Location: EasternMorocco. Methods: We measured relative abundance and functional traits along a short aridity gradient over two consecutive years at five heavily grazed sites, eachwith an exclosure preventing grazing. We analysed the relationship between aridity, grazing, and the expression of CWMtrait values using ordinationmethods and a fourth-corner analysis. Results: Unconstrained and constrained ordinations identified three distinct suites of temporally consistent functional traits that co-varied with aridity and grazing, and the fourth-corner analysis identified a number of significant but weak trait-environment associations. Grazing selected for short, fast-growing annual species with high SLA, high pastoral value and low seed mass, while aridity selected for species possessing succulent leaves with high d 13 C leaf content, spines, low LDMC and short stature, although the relative importance of precipitation and grazing changed between years. Conclusions: Although distinct from more mesic grasslands, our study sites exhibited patterns of trait correlations that were similar to the worldwide leaf economics spectrum. These correlation patterns represented three groups that were reminiscent of Grime's C-S-R model. Direct ordinations supported this interpretation. Temporal variation in our results was due in part to precipitation fluctuations. Our results also indicated selection for a grazing avoidance strategy under heavy grazing. Integrating plant functional traits in conservation and management of arid ecosystems represents a novel and challenging task to ensuremore sustainable use of these lands.

2. To answer those questions, we conducted a common-garden decomposition experiment bringing together leaves, fine stems, coarse stems, fine roots and reproductive parts from a wide range of subarctic plant types, clades and environments. We measured all plant parts for the same (green and litter) plant economics traits and identified a whole-plant axis of carbon and nutrient economics.3. We demonstrated that our local 'PES' has important afterlife effects on carbon turnover by driving coordinated decomposition rates of different organs across species. All organ decomposabilities were consistently controlled by the same structure-related traits (lignin, C and dry matter content) whilst nutrient-related traits (N, P, pH, phenols) had more variable influence, likely due to their contrasting functions across organs. Nevertheless, consistent shifts in elevation of parallel trait-decomposition relationships between organs indicate that other variables, potentially related to organ dimensions, configuration or chemical contents, codetermine litter decomposition rates.4. Whilst the coordinated litter decomposabilities across species organs imply a coordinated impact of plant above-ground and below-ground litters on plant-soil feedbacks, the contrasting decomposabilities between plant parts suggest a major role for the relative inputs of organ litter as driver of soil properties and ecosystem biogeochemistry. These relationships, underpinning the afterlife effects of the PES on whole-plant litter decomposability, will provide comprehensive input of vegetation composition feedback to soil carbon turnover.]]>2. To answer those questions, we conducted a common-garden decomposition experiment bringing together leaves, fine stems, coarse stems, fine roots and reproductive parts from a wide range of subarctic plant types, clades and environments. We measured all plant parts for the same (green and litter) plant economics traits and identified a whole-plant axis of carbon and nutrient economics.3. We demonstrated that our local 'PES' has important afterlife effects on carbon turnover by driving coordinated decomposition rates of different organs across species. All organ decomposabilities were consistently controlled by the same structure-related traits (lignin, C and dry matter content) whilst nutrient-related traits (N, P, pH, phenols) had more variable influence, likely due to their contrasting functions across organs. Nevertheless, consistent shifts in elevation of parallel trait-decomposition relationships between organs indicate that other variables, potentially related to organ dimensions, configuration or chemical contents, codetermine litter decomposition rates.4. Whilst the coordinated litter decomposabilities across species organs imply a coordinated impact of plant above-ground and below-ground litters on plant-soil feedbacks, the contrasting decomposabilities between plant parts suggest a major role for the relative inputs of organ litter as driver of soil properties and ecosystem biogeochemistry. These relationships, underpinning the afterlife effects of the PES on whole-plant litter decomposability, will provide comprehensive input of vegetation composition feedback to soil carbon turnover.]]>2. To answer those questions, we conducted a common-garden decomposition experiment bringing together leaves, fine stems, coarse stems, fine roots and reproductive parts from a wide range of subarctic plant types, clades and environments. We measured all plant parts for the same (green and litter) plant economics traits and identified a whole-plant axis of carbon and nutrient economics.3. We demonstrated that our local 'PES' has important afterlife effects on carbon turnover by driving coordinated decomposition rates of different organs across species. All organ decomposabilities were consistently controlled by the same structure-related traits (lignin, C and dry matter content) whilst nutrient-related traits (N, P, pH, phenols) had more variable influence, likely due to their contrasting functions across organs. Nevertheless, consistent shifts in elevation of parallel trait-decomposition relationships between organs indicate that other variables, potentially related to organ dimensions, configuration or chemical contents, codetermine litter decomposition rates.4. Whilst the coordinated litter decomposabilities across species organs imply a coordinated impact of plant above-ground and below-ground litters on plant-soil feedbacks, the contrasting decomposabilities between plant parts suggest a major role for the relative inputs of organ litter as driver of soil properties and ecosystem biogeochemistry. These relationships, underpinning the afterlife effects of the PES on whole-plant litter decomposability, will provide comprehensive input of vegetation composition feedback to soil carbon turnover.]]>

The leaf economics spectrum (LES) has revolutionized the way many ecologists think about quantifying plant ecological trade-offs. In particular, the LES has connected a clear functional trade-off (long-lived leaves with slow carbon capture vs. short-lived leaves with fast carbon capture) to a handful of easily measured leaf traits. Building on this work, community ecologists are now able to quickly assess species carbon-capture strategies, which may have implications for community-level patterns such as competition or succession. However, there are a number of steps in this logic that require careful examination, and a potential danger arises when interpreting leaf-trait variation among species within communities where trait relationships are weak. Using data from 22 diverse communities, we show that relationships among three common functional traits (photosynthetic rate, leaf nitrogen concentration per mass, leaf mass per area) are weak in communities with low variation in leaf life span (LLS), especially communities dominated by herbaceous or deciduous woody species. However, globally there are few LLS data sets for communities dominated by herbaceous or deciduous species, and more data are needed to confirm this pattern. The context-dependent nature of trait relationships at the community level suggests that leaf-trait variation within communities, especially those dominated by herbaceous and deciduous woody species, should be interpreted with caution.

Location;University of KwaZulu-Natal, Pietermaritzburg, South Africa.Methods;Using several pot experiments involving 29 grass species in total, we determined the vegetative traits, competitive effect and response, and tolerance to shading for grasses common in closed, tufted mesic grassland in KZN.Results;The primary axis of grass-trait variation was most strongly related to a negative correlation (trade-off) between growth rate and specific leaf area (SLA), with broad-leaved, rapidly-growing grasses (high SLA) occupying one extreme and narrow-leaved, slow-growing grasses (low SLA) the other extreme of the first principal component. The low SLA, slow-growth strategy was found to be a relatively general strategy among grasses dominant in undisturbed, high litter grassland, as well as those adapted to moisture-stressed habitats. In contrast, grasses dominant in highly productive habitats with some form of disturbance, e.g. mowing, had a broad-leaved, rapid-growth strategy. Intermediate combinations of the SLA-growth rate trade-off were common among grasses dominant under other combinations of disturbance and soil resource availability.Conclusions;Distinct patterns of organismal (SLA, growth rate) and specific process (competitive effect and response, as well as tolerance of shading) responses appeared to be associated with grasses dominant on gradients of burning, mowing, fertilization and soil depth. These organismal and specific process responses were similar to those for North American and European grasses dominant under the same environmental influences, suggesting that some general trait-environment patterns exist at an inter-continental scale. This general trait-environment relationship appears to be driven by functional adaptive selection along the SLA-environment continuum and its unavoidable trade-off with growth rate.]]>Location;University of KwaZulu-Natal, Pietermaritzburg, South Africa.Methods;Using several pot experiments involving 29 grass species in total, we determined the vegetative traits, competitive effect and response, and tolerance to shading for grasses common in closed, tufted mesic grassland in KZN.Results;The primary axis of grass-trait variation was most strongly related to a negative correlation (trade-off) between growth rate and specific leaf area (SLA), with broad-leaved, rapidly-growing grasses (high SLA) occupying one extreme and narrow-leaved, slow-growing grasses (low SLA) the other extreme of the first principal component. The low SLA, slow-growth strategy was found to be a relatively general strategy among grasses dominant in undisturbed, high litter grassland, as well as those adapted to moisture-stressed habitats. In contrast, grasses dominant in highly productive habitats with some form of disturbance, e.g. mowing, had a broad-leaved, rapid-growth strategy. Intermediate combinations of the SLA-growth rate trade-off were common among grasses dominant under other combinations of disturbance and soil resource availability.Conclusions;Distinct patterns of organismal (SLA, growth rate) and specific process (competitive effect and response, as well as tolerance of shading) responses appeared to be associated with grasses dominant on gradients of burning, mowing, fertilization and soil depth. These organismal and specific process responses were similar to those for North American and European grasses dominant under the same environmental influences, suggesting that some general trait-environment patterns exist at an inter-continental scale. This general trait-environment relationship appears to be driven by functional adaptive selection along the SLA-environment continuum and its unavoidable trade-off with growth rate.]]>Location;University of KwaZulu-Natal, Pietermaritzburg, South Africa.Methods;Using several pot experiments involving 29 grass species in total, we determined the vegetative traits, competitive effect and response, and tolerance to shading for grasses common in closed, tufted mesic grassland in KZN.Results;The primary axis of grass-trait variation was most strongly related to a negative correlation (trade-off) between growth rate and specific leaf area (SLA), with broad-leaved, rapidly-growing grasses (high SLA) occupying one extreme and narrow-leaved, slow-growing grasses (low SLA) the other extreme of the first principal component. The low SLA, slow-growth strategy was found to be a relatively general strategy among grasses dominant in undisturbed, high litter grassland, as well as those adapted to moisture-stressed habitats. In contrast, grasses dominant in highly productive habitats with some form of disturbance, e.g. mowing, had a broad-leaved, rapid-growth strategy. Intermediate combinations of the SLA-growth rate trade-off were common among grasses dominant under other combinations of disturbance and soil resource availability.Conclusions;Distinct patterns of organismal (SLA, growth rate) and specific process (competitive effect and response, as well as tolerance of shading) responses appeared to be associated with grasses dominant on gradients of burning, mowing, fertilization and soil depth. These organismal and specific process responses were similar to those for North American and European grasses dominant under the same environmental influences, suggesting that some general trait-environment patterns exist at an inter-continental scale. This general trait-environment relationship appears to be driven by functional adaptive selection along the SLA-environment continuum and its unavoidable trade-off with growth rate.]]>

Methods: We conducted ameta-analysis on 18 studies (consisting of 38 species) of plant biomass response to experimental or natural warming. We determined whether plant trait estimates associated with the leaf economics spectrum [leaf life span (LL), leaf mass per area (LMA), leaf nitrogen (N-mass), leaf phosphorus (P-mass), photosynthetic capacity (A(max)) and stomatal conductance (G(s))] from a global plant database of experimentally unmanipulated plants, GloPNet, could be used to predict biomass response to experimental warming.Results: We found that three single leaf traits (LL, Nmass and Amax) were significant predictors for the response of plant biomass to warming treatments, perhaps due to their association with plant growth rates, adaptation rate and ability, each explaining between 21-46% of the variation in plant biomass responses. The magnitude of response to warming decreased with increasing LL, but increased with increasing Nmass and Amax. We found no linear combination of any of these traits that predicted warming response.Conclusions: These results show that foliar traits can aid in understanding the mechanisms by which plants respond to temperature across species. Because each trait only explained a portion of variation in how plant growth responded to warming, however, future studies that examine how plant communities respond to warming should simultaneously measure multiple leaf traits, especially those most sensitive to warming, across plant species, to determine whether the predictive ability of functional traits changes between different ecosystems or plant taxonomic groups.]]>Methods: We conducted ameta-analysis on 18 studies (consisting of 38 species) of plant biomass response to experimental or natural warming. We determined whether plant trait estimates associated with the leaf economics spectrum [leaf life span (LL), leaf mass per area (LMA), leaf nitrogen (N-mass), leaf phosphorus (P-mass), photosynthetic capacity (A(max)) and stomatal conductance (G(s))] from a global plant database of experimentally unmanipulated plants, GloPNet, could be used to predict biomass response to experimental warming.Results: We found that three single leaf traits (LL, Nmass and Amax) were significant predictors for the response of plant biomass to warming treatments, perhaps due to their association with plant growth rates, adaptation rate and ability, each explaining between 21-46% of the variation in plant biomass responses. The magnitude of response to warming decreased with increasing LL, but increased with increasing Nmass and Amax. We found no linear combination of any of these traits that predicted warming response.Conclusions: These results show that foliar traits can aid in understanding the mechanisms by which plants respond to temperature across species. Because each trait only explained a portion of variation in how plant growth responded to warming, however, future studies that examine how plant communities respond to warming should simultaneously measure multiple leaf traits, especially those most sensitive to warming, across plant species, to determine whether the predictive ability of functional traits changes between different ecosystems or plant taxonomic groups.]]>Methods: We conducted ameta-analysis on 18 studies (consisting of 38 species) of plant biomass response to experimental or natural warming. We determined whether plant trait estimates associated with the leaf economics spectrum [leaf life span (LL), leaf mass per area (LMA), leaf nitrogen (N-mass), leaf phosphorus (P-mass), photosynthetic capacity (A(max)) and stomatal conductance (G(s))] from a global plant database of experimentally unmanipulated plants, GloPNet, could be used to predict biomass response to experimental warming.Results: We found that three single leaf traits (LL, Nmass and Amax) were significant predictors for the response of plant biomass to warming treatments, perhaps due to their association with plant growth rates, adaptation rate and ability, each explaining between 21-46% of the variation in plant biomass responses. The magnitude of response to warming decreased with increasing LL, but increased with increasing Nmass and Amax. We found no linear combination of any of these traits that predicted warming response.Conclusions: These results show that foliar traits can aid in understanding the mechanisms by which plants respond to temperature across species. Because each trait only explained a portion of variation in how plant growth responded to warming, however, future studies that examine how plant communities respond to warming should simultaneously measure multiple leaf traits, especially those most sensitive to warming, across plant species, to determine whether the predictive ability of functional traits changes between different ecosystems or plant taxonomic groups.]]>

Plant functional traits involved in carbon and water acquisition are likely to be adaptive across the range of a species if the availability of these resources varies across this range and are limiting to growth or fitness. At the interspecific level, leaf economic traits associated with rapid resource capture are correlated with fast growth rates. However, relationships between leaf traits and growth are poorly understood at the intraspecific level. We examined two hypotheses: (i) leaf traits vary genotypically among Populus fremontii populations from different thermal environments; and (ii) leaf traits are related to growth rate of these P.fremontii populations. We used a common garden at the warm edge of P.fremontii distribution that included individuals transplanted from 11 provenances. Provenances varied in mean annual maximum temperature by 5 center dot 9 degrees C, reflecting a range of expected increases in temperature over the next 80years. Conservative leaf traits (e.g. low specific leaf area, N content, stomatal conductance, net photosynthetic rate and high leaf water-use efficiency) were positively related to growth rates of genotypes and populations, a pattern opposite of that widely reported among species in other studies. Provenance temperature explained 75% of the variation in multivariate leaf traits with the warmest provenances having the most conservative traits and highest growth rates. Clinal genetic variation suggests that P.fremontii may be adapted to thermal environments. Leaf area-to-sapwood area ratio was positively associated with growth rate, while leaf area-based net photosynthetic rate was negatively associated with growth rate; these results suggest that hydraulic architecture was more important than leaf-level photosynthetic rate in determining growth rate. Synthesis. Our results suggest that conservative leaf traits promote rapid growth of P.fremontii genotypes in extremely hot environments. Thus, relationships between leaf economic traits among species do not necessarily apply to the range of variation among genotypes within species. The generality of this pattern should be examined for other species that will be exposed to climate warming. Moreover, our research shows that common garden provenance trials are useful for identifying genotypes best suited to a predicted warmer climate and for improving understanding of the physiological basis for adaptation to warm environments.

Life history theory predicts the evolution of trait combinations that enhance fitness, and the occurrence of trade-offs depends in part on the magnitude of variation in growth rate or acquisition. Using recombinant inbred lines, we examined the genetic architecture of age and size at reproduction across abiotic conditions encountered by cultivars and naturalized populations of Brassica rapa. We found that genotypes are plastic to seasonal setting, such that reproduction was accelerated under conditions encountered by summer annual populations and genetic variances for age at reproduction varied across simulated seasonal settings. Using an acquisition-allocation model, we predicted the likelihood of trade-offs. Consistent with predicted relationships, we observed a trade-off where early maturity is associated with small size at maturity under simulated summer and fall annual conditions but not under winter annual conditions. The trade-off in the summer annual setting was observed despite significant genotypic variation in growth rate, which is often expected to decouple age and size at reproduction because rapidly growing genotypes could mature early and attain a larger size relative to slowly growing genotypes that mature later. The absence of a trade-off in the winter setting is presumably attributable to the absence of genotypic differences in age at reproduction. We observed QTL for age at reproduction that jointly regulated size at reproduction in both the summer and fall annual settings, but these QTL were environment-specific (i.e. different QTL contributed to the trade-off in the fall vs. summer annual settings). Thus, at least some of the genetic mechanisms underlying observed trade-offs differed across environments.

Although broad-scale inter-specific patterns of leaf traits are influenced by climate, soil, and taxonomic identity, integrated assessments of these drivers remain rare. Here, we quantify these drivers in a field study of 171 plant species in 174 sites across Chinese grasslands, including the Tibetan Plateau, Inner Mongolia, and Xinjiang. General linear models were used to partition leaf trait variation. Of the total variation in leaf traits, on average 27% is due to taxonomic or phylogenetic differences among species within sites (pure species effect), 29% to variation among sites within species (pure site effect), 38% to joint effects of taxonomic and environmental factors (shared effect), and 6.2% to within-site and within-species variation. Examining the pure site effect, climate explained 7.8%, soil explained 7.4%, and climate and soil variables together accounted for 11%, leaving 18% of the inter-site variation due to factors other than climate or soil. The results do not support the hypothesis that soil fertility is the “missing link” to explain leaf trait variation unexplained by climatic factors. Climate- and soil-induced leaf adaptations occur mostly among species, and leaf traits vary little within species in Chinese grassland plants, despite strongly varying climate and soil conditions.

Aim The world-wide leaf economic spectrum (LES) describes tight coordination of leaf traits across global floras, reported to date as being largely independent of phylogeny and biogeography. Here, we present and test an alternative, historical perspective that predicts that biogeography places significant constraints on global trait evolution. These hypothesized constraints could lead to important deviations in leaf trait relationships between isolated floras that were influenced by different magnitudes of genetic constraint and selection. Location Global, including floristic regions of the Northern and Southern Hemispheres, eastern North America, East Asia (EAS), the Hawaiian Islands and tropical mainland floras. Methods We use a large leaf-trait database (GLOPNET) and species native distribution data to test for variation in leaf trait relationships modulated by floristic region, controlling for climatic differences. Standardized major axis analyses were used to evaluate biogeographic effects on bivariate relationships between LES traits, including relationships of photosynthetic capacity and dark respiration rate (AmassRd-mass), leaf lifespan and mass per area ratio (LLLMA), and photosynthetic capacity and nitrogen content (AmassNmass). Results Independent of climate or biome, floras of different evolutionary histories exhibited different leaf trait allometries. Floras of the Northern Hemisphere exhibited greater rates of return on resource investment (steeper slopes for the trait relationships analysed), and the more diverse temperate EAS flora exhibited greater slopes or intercepts in leaf trait relationships, with the exception of the AmassNmass relationship. In contrast to our hypothesis, plants of the floristically isolated Hawaiian Islands exhibited a similar AmassNmass relationship to those of mainland tropical regions. Main conclusions Differences in leaf trait allometries among global floristic regions support a historical perspective in understanding leaf trait relationships and suggest that independent floras can exhibit different tradeoffs in resource capture strategies.

Studies in disturbed, resource-rich environments often show that invasive plants are more productive than co-occurring natives, but with similar physiological tradeoffs. However, in resource-limited habitats, it is unclear whether native and invasive plants have similar metabolic constraints or if invasive plants are more productive per unit resource cost - that is, use resources more efficiently. Using a common garden to control for environment, we compared leaf physiological traits relating to resource investments, carbon returns, and resource-use efficiencies in 14 native and 18 nonnative invasive species of common genera found in Eastern North American (ENA) deciduous forest understories, where growth is constrained by light and nutrient limitation. Despite greater leaf construction and nitrogen costs, invaders exhibited greater instantaneous photosynthetic energy-use efficiency (PEUE) and marginally greater photosynthetic nitrogen-use efficiency (PNUE). When integrated over leaf lifespan (LL), these differences were magnified. Differences in efficiency were driven by greater productivity per unit leaf investment, as invaders exhibited both greater photosynthetic abilities and longer LL. Our results indicate that woody understory invaders in ENA forests are not constrained to the same degree by leaf-based metabolic tradeoffs as the native understory flora. These strategy differences could be attributable to pre-adaptation in the native range, although other explanations are possible.

AimsStipa purpurea is the dominant species in alpine arid and semi-arid grasslands on the Tibetan Plateau. Our objectives are to determine if this species exhibits a strategy shift in its specific leaf area (SLA) to nitrogen (N) concentration relationship along a rainfall gradient and to detect possible effects of environmental factors on related leaf traits. Methods We investigated variations in leaf traits of S. purpurea associated with climatic and soil factors along an east-west transect with a rainfall gradient (69–479 mm) but similar altitudes (4 300–4 700 m). Five locations from east to west are Damxung, Namco, Gêrzê, Mount Qomolangma and Rutog. We measured SLA, mass- and area-based leaf N concentration (Nmass, Narea), leaf density and thickness and soil total N along the transect. Important findings In pooled data, SLA and Nmass varied little with the growing season mean temperature and precipitation and the soil total N concentration. The SLA-Nmass relationship in S. purpurea did not shift between the semi-humid areas (ratio of rainfall to evaporation > 0.11) and the arid and semi-arid areas (ratio < 0.11), although there was a positive correlation between SLA and Nmass across the five locations. Variation in SLA was mainly determined by leaf density in the semi-humid areas and by leaf thickness in the arid and semi-arid areas; both were negatively correlated with SLA. With increasing temperature or declining precipitation, leaf density decreased and leaf thickness increased, leading to non-significant relationships between SLA and climatic factors. The increase of leaf density in the semi-humid areas was correlated with the increase of Narea, but the increase of leaf thickness in the arid and semi-arid areas did not lead to change of Narea, resulting in unchanged Narea along the rainfall gradient. A positive correlation was detected between aboveground biomass and Narea in S. purpurea, indicating that increased Narea may increase plant productivity. Our findings suggest that alpine plants in arid and semi-arid areas may maintain a constant Narea by increased leaf thickness in order to achieve a similar photosynthetic productivity and water use efficiency compared to the relatively humid areas. The relative impacts of leaf density and leaf thickness on SLA shifted between the semi-humid areas and the arid and semi-arid areas, which may provide insight in detecting the threshold of water limitation in alpine grasslands.]]>AimsStipa purpurea is the dominant species in alpine arid and semi-arid grasslands on the Tibetan Plateau. Our objectives are to determine if this species exhibits a strategy shift in its specific leaf area (SLA) to nitrogen (N) concentration relationship along a rainfall gradient and to detect possible effects of environmental factors on related leaf traits. Methods We investigated variations in leaf traits of S. purpurea associated with climatic and soil factors along an east-west transect with a rainfall gradient (69–479 mm) but similar altitudes (4 300–4 700 m). Five locations from east to west are Damxung, Namco, Gêrzê, Mount Qomolangma and Rutog. We measured SLA, mass- and area-based leaf N concentration (Nmass, Narea), leaf density and thickness and soil total N along the transect. Important findings In pooled data, SLA and Nmass varied little with the growing season mean temperature and precipitation and the soil total N concentration. The SLA-Nmass relationship in S. purpurea did not shift between the semi-humid areas (ratio of rainfall to evaporation > 0.11) and the arid and semi-arid areas (ratio < 0.11), although there was a positive correlation between SLA and Nmass across the five locations. Variation in SLA was mainly determined by leaf density in the semi-humid areas and by leaf thickness in the arid and semi-arid areas; both were negatively correlated with SLA. With increasing temperature or declining precipitation, leaf density decreased and leaf thickness increased, leading to non-significant relationships between SLA and climatic factors. The increase of leaf density in the semi-humid areas was correlated with the increase of Narea, but the increase of leaf thickness in the arid and semi-arid areas did not lead to change of Narea, resulting in unchanged Narea along the rainfall gradient. A positive correlation was detected between aboveground biomass and Narea in S. purpurea, indicating that increased Narea may increase plant productivity. Our findings suggest that alpine plants in arid and semi-arid areas may maintain a constant Narea by increased leaf thickness in order to achieve a similar photosynthetic productivity and water use efficiency compared to the relatively humid areas. The relative impacts of leaf density and leaf thickness on SLA shifted between the semi-humid areas and the arid and semi-arid areas, which may provide insight in detecting the threshold of water limitation in alpine grasslands.]]>AimsStipa purpurea is the dominant species in alpine arid and semi-arid grasslands on the Tibetan Plateau. Our objectives are to determine if this species exhibits a strategy shift in its specific leaf area (SLA) to nitrogen (N) concentration relationship along a rainfall gradient and to detect possible effects of environmental factors on related leaf traits. Methods We investigated variations in leaf traits of S. purpurea associated with climatic and soil factors along an east-west transect with a rainfall gradient (69–479 mm) but similar altitudes (4 300–4 700 m). Five locations from east to west are Damxung, Namco, Gêrzê, Mount Qomolangma and Rutog. We measured SLA, mass- and area-based leaf N concentration (Nmass, Narea), leaf density and thickness and soil total N along the transect. Important findings In pooled data, SLA and Nmass varied little with the growing season mean temperature and precipitation and the soil total N concentration. The SLA-Nmass relationship in S. purpurea did not shift between the semi-humid areas (ratio of rainfall to evaporation > 0.11) and the arid and semi-arid areas (ratio < 0.11), although there was a positive correlation between SLA and Nmass across the five locations. Variation in SLA was mainly determined by leaf density in the semi-humid areas and by leaf thickness in the arid and semi-arid areas; both were negatively correlated with SLA. With increasing temperature or declining precipitation, leaf density decreased and leaf thickness increased, leading to non-significant relationships between SLA and climatic factors. The increase of leaf density in the semi-humid areas was correlated with the increase of Narea, but the increase of leaf thickness in the arid and semi-arid areas did not lead to change of Narea, resulting in unchanged Narea along the rainfall gradient. A positive correlation was detected between aboveground biomass and Narea in S. purpurea, indicating that increased Narea may increase plant productivity. Our findings suggest that alpine plants in arid and semi-arid areas may maintain a constant Narea by increased leaf thickness in order to achieve a similar photosynthetic productivity and water use efficiency compared to the relatively humid areas. The relative impacts of leaf density and leaf thickness on SLA shifted between the semi-humid areas and the arid and semi-arid areas, which may provide insight in detecting the threshold of water limitation in alpine grasslands.]]>

Stipa purpurea)为研究对象, 沿降水梯度(69–479 mm)系统测定了日土、改则、珠峰、当雄和纳木错5个调查地点紫花针茅比叶面积(SLA)、单位重量和单位面积叶氮含量(Nmass, Narea)、叶密度和厚度等叶功能性状以及土壤全氮含量等因子, 试图验证干旱胁迫地区同一物种内SLA-Nmass关系沿降水梯度的策略位移现象是否具有普遍性, 并对是否出现策略位移现象提出可能的解释。研究结果表明: 1) SLA和Nmass与生长季温度和降水以及土壤全氮含量均没有显著关系, SLA与Nmass的关系在干旱半干旱区(年降水/蒸发比< 0.11)与半湿润区(年降水/蒸发比> 0.11)之间并没有出现典型的位移现象; 2)叶密度是决定半湿润区SLA变化的主导因子, 而叶厚度则是干旱半干旱区SLA变化的控制因子, 两者与SLA均呈负相关, 随着温度增加或降水减少, 叶厚度增加而叶密度降低, 导致SLA随温度和降水变化不明显; 3)半湿润区的叶密度增加引起Narea增加, 而干旱半干旱区的叶厚度增加并没有造成Narea的显著变化, 导致Narea沿降水梯度没有显著变化; 4)紫花针茅地上生物量与Narea具有显著正相关关系, 表明Narea的增加有助于提高植被生产力。结果表明, 在干旱胁迫下, 植物通过增加叶厚度来维持不变的Narea可能有助于保持与较湿润地区相似的光合生产和水分利用效率。叶厚度和叶密度对比叶面积的相对影响在干旱半干旱区与半湿润区之间发生转变, 这为进一步检测高寒草地植被的水分限制阈值提供了新思路。]]>Stipa purpurea)为研究对象, 沿降水梯度(69–479 mm)系统测定了日土、改则、珠峰、当雄和纳木错5个调查地点紫花针茅比叶面积(SLA)、单位重量和单位面积叶氮含量(Nmass, Narea)、叶密度和厚度等叶功能性状以及土壤全氮含量等因子, 试图验证干旱胁迫地区同一物种内SLA-Nmass关系沿降水梯度的策略位移现象是否具有普遍性, 并对是否出现策略位移现象提出可能的解释。研究结果表明: 1) SLA和Nmass与生长季温度和降水以及土壤全氮含量均没有显著关系, SLA与Nmass的关系在干旱半干旱区(年降水/蒸发比< 0.11)与半湿润区(年降水/蒸发比> 0.11)之间并没有出现典型的位移现象; 2)叶密度是决定半湿润区SLA变化的主导因子, 而叶厚度则是干旱半干旱区SLA变化的控制因子, 两者与SLA均呈负相关, 随着温度增加或降水减少, 叶厚度增加而叶密度降低, 导致SLA随温度和降水变化不明显; 3)半湿润区的叶密度增加引起Narea增加, 而干旱半干旱区的叶厚度增加并没有造成Narea的显著变化, 导致Narea沿降水梯度没有显著变化; 4)紫花针茅地上生物量与Narea具有显著正相关关系, 表明Narea的增加有助于提高植被生产力。结果表明, 在干旱胁迫下, 植物通过增加叶厚度来维持不变的Narea可能有助于保持与较湿润地区相似的光合生产和水分利用效率。叶厚度和叶密度对比叶面积的相对影响在干旱半干旱区与半湿润区之间发生转变, 这为进一步检测高寒草地植被的水分限制阈值提供了新思路。]]>Stipa purpurea)为研究对象, 沿降水梯度(69–479 mm)系统测定了日土、改则、珠峰、当雄和纳木错5个调查地点紫花针茅比叶面积(SLA)、单位重量和单位面积叶氮含量(Nmass, Narea)、叶密度和厚度等叶功能性状以及土壤全氮含量等因子, 试图验证干旱胁迫地区同一物种内SLA-Nmass关系沿降水梯度的策略位移现象是否具有普遍性, 并对是否出现策略位移现象提出可能的解释。研究结果表明: 1) SLA和Nmass与生长季温度和降水以及土壤全氮含量均没有显著关系, SLA与Nmass的关系在干旱半干旱区(年降水/蒸发比< 0.11)与半湿润区(年降水/蒸发比> 0.11)之间并没有出现典型的位移现象; 2)叶密度是决定半湿润区SLA变化的主导因子, 而叶厚度则是干旱半干旱区SLA变化的控制因子, 两者与SLA均呈负相关, 随着温度增加或降水减少, 叶厚度增加而叶密度降低, 导致SLA随温度和降水变化不明显; 3)半湿润区的叶密度增加引起Narea增加, 而干旱半干旱区的叶厚度增加并没有造成Narea的显著变化, 导致Narea沿降水梯度没有显著变化; 4)紫花针茅地上生物量与Narea具有显著正相关关系, 表明Narea的增加有助于提高植被生产力。结果表明, 在干旱胁迫下, 植物通过增加叶厚度来维持不变的Narea可能有助于保持与较湿润地区相似的光合生产和水分利用效率。叶厚度和叶密度对比叶面积的相对影响在干旱半干旱区与半湿润区之间发生转变, 这为进一步检测高寒草地植被的水分限制阈值提供了新思路。]]>

Despite recent progress in characterizing the within-species variability (WSV) of plant functional traits, the importance of this WSV in driving ecological processes such as leaf litter decomposability within species or at the whole community level is poorly understood.We ask whether leaf and litter functional traits vary within species to form a spectrum of variability analogous to the leaf economics spectrum that occurs among species. We also ask whether this spectrum of trait variation within species is an important driver of leaf litter decomposability. To address these questions, we quantified both WSV and between-species variation of leaf and litter traits and litter decomposability of 16 co-occurring temperate rain forest plant species along soil toposequences characterized by strong shifts in soil nutrient status in New Zealand.We found considerable WSV of both leaf and litter traits for all species, and a within-species spectrum of coordinated trait variation for 11 species. The WSV of leaf and to a lesser extent foliar litter C to N and C to P values were often strongly related to soil C to N and C to P ratios across plots. Further, in many cases, WSV and its covariation with species turnover contributed significantly to the community-level aggregate trait response to variation in soil fertility.Contrary to our expectations, the WSV in leaf and litter traits did not generally predict within-species variation in leaf litter mass loss, nor N and P release, during decomposition. Further, inclusion of WSV did not improve predictions of leaf litter decomposability using community-level trait measures.Synthesis. Our findings support the view that WSV of plant functional traits is an important component of plant community responses to environmental factors such as soil fertility. However, the apparent decoupling of WSV of leaf economic traits from WSV of ecological processes such as litter decomposability suggests that consideration of WSV may not be necessary to understand the contributions of trait variation to determining the breakdown of plant litter and therefore, potentially, ecosystem processes.]]>Despite recent progress in characterizing the within-species variability (WSV) of plant functional traits, the importance of this WSV in driving ecological processes such as leaf litter decomposability within species or at the whole community level is poorly understood.We ask whether leaf and litter functional traits vary within species to form a spectrum of variability analogous to the leaf economics spectrum that occurs among species. We also ask whether this spectrum of trait variation within species is an important driver of leaf litter decomposability. To address these questions, we quantified both WSV and between-species variation of leaf and litter traits and litter decomposability of 16 co-occurring temperate rain forest plant species along soil toposequences characterized by strong shifts in soil nutrient status in New Zealand.We found considerable WSV of both leaf and litter traits for all species, and a within-species spectrum of coordinated trait variation for 11 species. The WSV of leaf and to a lesser extent foliar litter C to N and C to P values were often strongly related to soil C to N and C to P ratios across plots. Further, in many cases, WSV and its covariation with species turnover contributed significantly to the community-level aggregate trait response to variation in soil fertility.Contrary to our expectations, the WSV in leaf and litter traits did not generally predict within-species variation in leaf litter mass loss, nor N and P release, during decomposition. Further, inclusion of WSV did not improve predictions of leaf litter decomposability using community-level trait measures.Synthesis. Our findings support the view that WSV of plant functional traits is an important component of plant community responses to environmental factors such as soil fertility. However, the apparent decoupling of WSV of leaf economic traits from WSV of ecological processes such as litter decomposability suggests that consideration of WSV may not be necessary to understand the contributions of trait variation to determining the breakdown of plant litter and therefore, potentially, ecosystem processes.]]>Despite recent progress in characterizing the within-species variability (WSV) of plant functional traits, the importance of this WSV in driving ecological processes such as leaf litter decomposability within species or at the whole community level is poorly understood.We ask whether leaf and litter functional traits vary within species to form a spectrum of variability analogous to the leaf economics spectrum that occurs among species. We also ask whether this spectrum of trait variation within species is an important driver of leaf litter decomposability. To address these questions, we quantified both WSV and between-species variation of leaf and litter traits and litter decomposability of 16 co-occurring temperate rain forest plant species along soil toposequences characterized by strong shifts in soil nutrient status in New Zealand.We found considerable WSV of both leaf and litter traits for all species, and a within-species spectrum of coordinated trait variation for 11 species. The WSV of leaf and to a lesser extent foliar litter C to N and C to P values were often strongly related to soil C to N and C to P ratios across plots. Further, in many cases, WSV and its covariation with species turnover contributed significantly to the community-level aggregate trait response to variation in soil fertility.Contrary to our expectations, the WSV in leaf and litter traits did not generally predict within-species variation in leaf litter mass loss, nor N and P release, during decomposition. Further, inclusion of WSV did not improve predictions of leaf litter decomposability using community-level trait measures.Synthesis. Our findings support the view that WSV of plant functional traits is an important component of plant community responses to environmental factors such as soil fertility. However, the apparent decoupling of WSV of leaf economic traits from WSV of ecological processes such as litter decomposability suggests that consideration of WSV may not be necessary to understand the contributions of trait variation to determining the breakdown of plant litter and therefore, potentially, ecosystem processes.]]>

Interannual variability in aboveground net primary production (ANPP) was assessed with long-term (mean = 12 years) data from 11 Long Term Ecological Research sites across North America. The greatest interannual variability in ANPP occurred in grasslands and old fields, with forests the least variable. At a continental scale, ANPP was strongly correlated with annual precipitation. However, interannual variability in ANPP was not related to variability in precipitation. Instead, maximum variability in ANPP occurred in biomes where high potential growth rates of herbaceous vegetation were combined with moderate variability in precipitation. In the most dynamic biomes, ANPP responded more strongly to wet than to dry years. Recognition of the fourfold range in ANPP dynamics across biomes and of the factors that constrain this variability is critical for detecting the biotic impacts of global change phenomena.

Tree and shrub species can be differentiated into two major groups based on their substantially different leaf anatomy: heterobaric and homobaric. In contrast to homobaric leaves, heterobaric leaves have bundle sheath extensions (BSEs) that create transparent regions on their lamina. Recent studies have shown that BSEs transfer visible light to internal mesophyll layers, thus affecting the photosynthetic performance of heterobaric leaves. Whether the two leaf types also differ in other functional and structural traits has not been addressed, nor have any structure-function relations. Here, we measured key anatomical and physiological parameters and tested their relationships in 30 species with different leaf types. Heterobaric leaves were thinner with lower leaf mass per area, had higher nitrogen concentration per mass, were (13)C-enriched, and achieved comparable photosynthetic capacity per area but had higher photosynthetic capacity per mass compared to homobaric leaves. Relations between leaf construction cost, nitrogen concentration, and photosynthesis followed the general pattern of the

The leaf economics spectrum (LES) describes large cross-species variation in suites of leaf functional traits ranging from resource-acquisitive to resource-conservative strategies. Such strategies have been integral in explaining plant adaptation to diverse environments, and have been linked to numerous ecosystem processes. The LES has previously been found to be significantly modulated by climate, soil fertility, biogeography, growth form, and life history. One largely unexplored aspect of LES variation, whole-plant ontogeny, is investigated here using multiple populations of three very different species of sunflower: Helianthus annuus, Helianthus mollis, and Helianthus radula. Plants were grown under environmentally controlled conditions and assessed for LES and related traits at four key developmental stages, using recently matured leaves to standardize for leaf age. Nearly every trait exhibited a significant ontogenetic shift in one or more species, with trait patterns differing among populations and species. Photosynthetic rate, leaf nitrogen concentration, and leaf mass per area exhibited surprisingly large changes, spanning over two-thirds of the original cross-species LES variation and shifting from resource-acquisitive to resource-conservative strategies as the plants matured. Other traits being investigated in relation to the LES, such as leaf water content, pH, and vein density, also showed large changes. The finding that ontogenetic variation in LES strategy can be substantial leads to a recommendation of standardization by developmental stage when assessing 'species values' of labile traits for comparative approaches. Additionally, the substantial ontogenetic trait shifts seen within single individuals provide an opportunity to uncover the contribution of gene regulatory changes to variation in LES traits.

Despite the increasing importance of functional traits for the study of plant ecology, we do not know how variation in a given trait changes across ecological scales, which prevents us from assessing potential scale-dependent aspects of trait variation. To address this deficiency, we partitioned the variance in two key functional traits (leaf mass area and leaf dry matter content) across six nested ecological scales (site, plot, species, tree, strata and leaf) in lowland tropical rainforests. In both traits, the plot level shows virtually no variance despite high species turnover among plots and the size of within-species variation (leaf + strata + tree) is comparable with that of species level variation. The lack of variance at the plot level brings substantial support to the idea that trait-based environmental filtering plays a central role in plant community assembly. These results and the finding that the amount of within-species variation is comparable with interspecific variation support a shift of focus from species-based to trait-based ecology.

The aim of this study was to detect suites of traits related to whole plant and seed morphology, phenology and resource use--including water--in species differing in successional status. Twenty traits were measured on 55 species representative of 5 successional stages in Mediterranean southern France, including eight pertaining to phenology and five to water economy. Suites of traits that changed along succession in agreement with the acquisition/conservation trade-off were completed by continuous changes in phenology. Early successional species had leaves with a high specific leaf area that were produced and lost continuously through the growing season. Late-successional species were taller with long-lived, high delta(13)C leaves produced during short periods, most of them persisting during summer, and produced large seeds requiring a long ripening period. Replacement of species occurred with change in strategies of drought survival: early successional species escaped drought by dying before summer; later herbaceous species maintained favourable water status in relation to leaf shedding during summer; late successional trees with a large body allowing access to a large pool of resources, produced dense leaves that could tolerate desiccation. These changes occurred concomitantly with a shift in CSR strategies, using traits related to resource use, plant size and flowering phenology: ruderal herbs were replaced by more stress-tolerant herbs and shrubs throughout the succession, with competitive trees dominating the latest successional stage. These results suggest that the breadth of functional variability found in natura is not predicted by the CSR framework, and calls for a more integrated view of whole plant functioning.

Foliage structure, chemistry, photosynthetic potentials (V(cmax) and J(max)), and mesophyll diffusion conductance (g(m)) were quantified for 35 broad-leaved species from four sites with contrasting rainfall and soil fertility in eastern Australia. The aim of the study was to estimate the extent to which g(m) and related leaf properties limited photosynthesis (A), focusing on highly sclerophyllous species typical of the 'slow-return' end of the leaf economics spectrum. Leaf dry mass per unit area (M(A)) varied approximately 5-fold, leaf life span (L(L)) and N (N(M)) and P (P(M)) contents per dry mass approximately 8-fold, and various characteristics of foliage photosynthetic machinery 6- to 12-fold across the data set. As is characteristic of the 'leaf economics spectrum', more robust leaves with greater M(A) and longevity were associated with lower nutrient contents and lower foliage photosynthetic potentials. g(m) was positively correlated with V(cmax) and J(max), and these correlations were stronger on a mass basis. Only g(m)/mass was negatively associated with M(A). CO(2) drawdown from substomatal cavities to chloroplasts (C(i)-C(C)) characterizing mesophyll CO(2) diffusion limitations was larger in leaves with greater M(A), lower g(m)/mass, and lower photosynthetic potentials. Relative limitation of A due to finite mesophyll diffusion conductance, i.e. 1-A(infinite g(m))/A(actual g(m)), was always >0.2 and up to 0.5 in leaves with most robust leaf structure, demonstrating the profound effect of finite g(m) on realized photosynthesis rates. Data from different sites were overlapping in bivariate relationships, and the variability of average values between the sites was less than among the species within the sites. Nevertheless, photosynthesis was more strongly limited by g(m) in low rain/high nutrient and high rain/low nutrient sites that supported vegetation with more sclerophyllous foliage. These data collectively highlight a strong relationship between leaf structure and g(m), and demonstrate that realized photosynthesis rates are strongly limited by g(m) in this highly sclerophyllous flora.

Leaf mechanical properties strongly influence leaf lifespan, plant-herbivore interactions, litter decomposition and nutrient cycling, but global patterns in their interspecific variation and underlying mechanisms remain poorly understood. We synthesize data across the three major measurement methods, permitting the first global analyses of leaf mechanics and associated traits, for 2819 species from 90 sites worldwide. Key measures of leaf mechanical resistance varied c. 500-800-fold among species. Contrary to a long-standing hypothesis, tropical leaves were not mechanically more resistant than temperate leaves. Leaf mechanical resistance was modestly related to rainfall and local light environment. By partitioning leaf mechanical resistance into three different components we discovered that toughness per density contributed a surprisingly large fraction to variation in mechanical resistance, larger than the fractions contributed by lamina thickness and tissue density. Higher toughness per density was associated with long leaf lifespan especially in forest understory. Seldom appreciated in the past, toughness per density is a key factor in leaf mechanical resistance, which itself influences plant-animal interactions and ecosystem functions across the globe.

The leaf economics spectrum (LES) describes multivariate correlations that constrain leaf traits of plant species primarily to a single axis of variation if data are normalized by leaf mass. We show that these traits are approximately distributed proportional to leaf area instead of mass, as expected for a light- and carbon dioxide-collecting organ. Much of the structure in the mass-normalized LES results from normalizing area-proportional traits by mass. Mass normalization induces strong correlations among area-proportional traits because of large variation among species in leaf mass per area (LMA). The high LMA variance likely reflects its functional relationship with leaf life span. A LES that is independent of mass- or area-normalization and LMA reveals physiological relationships that are inconsistent with those in global vegetation models designed to address climate change.

Understanding drivers of biodiversity patterns is of prime importance in this era of severe environmental crisis. More diverse plant communities have been postulated to represent a larger functional trait-space, more likely to sustain a diverse assembly of herbivore species. Here, we expand this hypothesis to integrate environmental, functional and phylogenetic variation of plant communities as factors explaining the diversity of lepidopteran assemblages along elevation gradients in the Swiss Western Alps. According to expectations, we found that the association between butterflies and their host plants is highly phylogenetically structured. Multiple regression analyses showed the combined effect of climate, functional traits and phylogenetic diversity in structuring butterfly communities. Furthermore, we provide the first evidence that plant phylogenetic beta diversity is the major driver explaining butterfly phylogenetic beta diversity. Along ecological gradients, the bottom up control of herbivore diversity is thus driven by phylogenetically structured turnover of plant traits as well as environmental variables.

BACKGROUND AND AIMS: Hydrophytes generally exhibit highly acquisitive leaf economics. However, a range of growth forms is evident, from small, free-floating and rapidly growing Lemniden to large, broad-leaved Nymphaeiden, denoting variability in adaptive strategies. Traits used to classify adaptive strategies in terrestrial species, such as canopy height, are not applicable to hydrophytes. We hypothesize that hydrophyte leaf size traits and economics exhibit sufficient overlap with terrestrial species to allow a common classification of plant functional types, sensu Grime's CSR theory. METHODS: Leaf morpho-functional traits were measured for 61 species from 47 water bodies in lowland continental, sub-alpine and alpine bioclimatic zones in southern Europe and compared against the full leaf economics spectrum and leaf size range of terrestrial herbs, and between hydrophyte growth forms. KEY RESULTS: Hydrophytes differed in the ranges and mean values of traits compared with herbs, but principal components analysis (PCA) demonstrated that both groups shared axes of trait variability: PCA1 encompassed size variation (area and mass), and PCA2 ranged from relatively dense, carbon-rich leaves to nitrogen-rich leaves of high specific leaf area (SLA). Most growth forms exhibited trait syndromes directly equivalent to herbs classified as R adapted, although Nymphaeiden ranged between C and SR adaptation. CONCLUSIONS: Our findings support the hypothesis that hydrophyte adaptive strategy variation reflects fundamental trade-offs in economics and size that govern all plants, and that hydrophyte adaptive strategies can be directly compared with terrestrial species by combining leaf economics and size traits.

The ecophysiological linkage of leaf phosphorus (P) to photosynthetic capacity (A (max)) and to the A (max)-nitrogen relation remains poorly understood. To address this issue we compiled published and unpublished field data for mass-based A (max), nitrogen (N) and P (n = 517 observations) from 314 species at 42 sites in 14 countries. Data were from four biomes: arctic, cold temperate, subtropical (including Mediterranean), and tropical. We asked whether plants with low P levels have low A (max), a shallower slope of the A (max)-N relationship, and whether these patterns have a geographic signature. On average, leaf P was substantially lower in the two warmer than in the two colder biomes, with the reverse true for N:P ratios. The evidence indicates that the response of A (max) to leaf N is constrained by low leaf P. Using a full factorial model for all data, A (max) was related to leaf N, but not to leaf P on its own, with a significant leaf N x leaf P interaction indicating that the response of A (max) to N increased with increasing leaf P. This was also found in analyses using one value per species per site, or by comparing only angiosperms or only woody plants. Additionally, the slope of the A (max)-N relationship was higher in the colder arctic and temperate than warmer tropical and subtropical biomes. Sorting data into low, medium, and high leaf P groupings also showed that the A (max)-N slope increases with leaf P. These analyses support claims that in P-limited ecosystems the A (max)-N relationship may be constrained by low P, and are consistent with laboratory studies that show P-deficient plants have limited ribulose-1,5-bisphosphate regeneration, a likely mechanism for the P influence upon the A (max)-N relation.

Plant diversity generally promotes biomass production, but how the shape of the response curve changes with time remains unclear. This is a critical knowledge gap because the shape of this relationship indicates the extent to which loss of the first few species will influence biomass production. Using two long-term (>/=13 years) biodiversity experiments, we show that the effects of diversity on biomass productivity increased and became less saturating over time. Our analyses suggest that effects of diversity-dependent ecosystem feedbacks and interspecific complementarity accumulate over time, causing high-diversity species combinations that appeared functionally redundant during early years to become more functionally unique through time. Consequently, simplification of diverse ecosystems will likely have greater negative impacts on ecosystem functioning than has been suggested by short-term experiments.

Using a database of 2510 measurements from 287 species, we assessed whether general relationships exist between mass-based dark respiration rate and nitrogen concentration for stems and roots, and if they do, whether they are similar to those for leaves. The results demonstrate strong respiration-nitrogen scaling relationships for all observations and for data averaged by species; for roots, stems and leaves examined separately; and for life-forms (woody, herbaceous plants) and phylogenetic groups (angiosperms, gymnosperms) considered separately. No consistent differences in the slopes of these log-log scaling relations were observed among organs or among plant groups, but respiration rates at any common nitrogen concentration were consistently lower on average in leaves than in stems or roots, indicating that organ-specific relationships should be used in models that simulate respiration based on tissue nitrogen concentrations. The results demonstrate both common and divergent aspects of tissue-level respiration-nitrogen scaling for leaves, stems and roots across higher land plants, which are important in their own right and for their utility in modelling carbon fluxes at local to global scales.

Plant functional traits capture important variation in plant strategy and function. Recent literature has revealed that within-species variation in traits is greater than previously supposed. However, we still have a poor understanding of how intraspecific variation is coordinated among different traits, and how it is driven by environment. We quantified intraspecific variation in wood density and five leaf traits underpinning the leaf economics spectrum (leaf dry matter content, leaf mass per unit area, size, thickness and density) within and among four widespread Nothofagus tree species in southern New Zealand. We tested whether intraspecific relationships between wood density and leaf traits followed widely reported interspecific relationships, and whether variation in these traits was coordinated through shared responses to environmental factors. Sample sites varied widely in environmental variables, including soil fertility (25-900 mg kg(-1) total P), precipitation (668-4875 mm yr(-1)), temperature (5.2-12.4 degrees C mean annual temperature) and latitude (41-46 degrees S). Leaf traits were strongly correlated with one another within species, but not with wood density. There was some evidence for a positive relationship between wood density and leaf tissue density and dry matter content, but no evidence that leaf mass or leaf size were correlated with wood density; this highlights that leaf mass per unit area cannot be used as a surrogate for component leaf traits such as tissue density. Trait variation was predicted by environmental factors, but not consistently among different traits; e.g., only leaf thickness and leaf density responded to the same environmental cues as wood density. We conclude that although intraspecific variation in wood density and leaf traits is strongly driven by environmental factors, these responses are not strongly coordinated among functional traits even across co-occurring, closely-related plant species.

Leaf vein traits are implicated in the determination of gas exchange rates and plant performance. These traits are increasingly considered as causal factors affecting the 'leaf economic spectrum' (LES), which includes the light-saturated rate of photosynthesis, dark respiration, foliar nitrogen concentration, leaf dry mass per area (LMA) and leaf longevity. This article reviews the support for two contrasting hypotheses regarding a key vein trait, vein length per unit leaf area (VLA). Recently, Blonder et al. (2011, 2013) proposed that vein traits, including VLA, can be described as the 'origin' of the LES by structurally determining LMA and leaf thickness, and thereby vein traits would predict LES traits according to specific equations. Careful re-examination of leaf anatomy, published datasets, and a newly compiled global database for diverse species did not support the 'vein origin' hypothesis, and moreover showed that the apparent power of those equations to predict LES traits arose from circularity. This review provides a 'flux trait network' hypothesis for the effects of vein traits on the LES and on plant performance, based on a synthesis of the previous literature. According to this hypothesis, VLA, while virtually independent of LMA, strongly influences hydraulic conductance, and thus stomatal conductance and photosynthetic rate. We also review (i) the specific physiological roles of VLA; (ii) the role of leaf major veins in influencing LES traits; and (iii) the role of VLA in determining photosynthetic rate per leaf dry mass and plant relative growth rate. A clear understanding of leaf vein traits provides a new perspective on plant function independently of the LES and can enhance the ability to explain and predict whole plant performance under dynamic conditions, with applications towards breeding improved crop varieties.

Rates of tissue-level function have been hypothesized to decline as trees grow older and larger, but relevant evidence to assess such changes remains limited, especially across a wide range of sizes from saplings to large trees. We measured functional traits of leaves and twigs of three cold-temperate deciduous tree species in Minnesota, USA, to assess how these vary with tree height. Individuals ranging from 0.13 to 20 m in height were sampled in both relatively open and closed canopy environments to minimize light differences as a potential driver of size-related differences in leaf and twig properties. We hypothesized that (H1) gas-exchange rates, tissue N concentration and leaf mass per unit area (LMA) would vary with tree size in a pattern reflecting declining function in taller trees, yet maintaining (H2) bivariate trait relations, common among species as characterized by the leaf economics spectrum. Taking these two ideas together yielded a third, integrated hypothesis that (H3) nitrogen (N) content and gas-exchange rates should decrease monotonically with tree size and LMA should increase. We observed increasing LMA and decreasing leaf and twig Rd with increasing size, which matched predictions from H1 and H3. However, opposite to our predictions, leaf and twig N generally increased with size, and thus had inverse relations with respiration, rather than the predicted positive relations. Two exceptions were area-based leaf N of Prunus serotina Ehrh. in gaps and mass-based leaf N of Quercus ellipsoidalis E. J. Hill in gaps, both of which showed qualitatively hump-shaped patterns. Finally, we observed hump-shaped relationships between photosynthetic capacity and tree height, not mirroring any of the other traits, except in the two cases highlighted above. Bivariate trait relations were weak intra-specifically, but were generally significant and positive for area-based traits using the pooled dataset. Results suggest that different traits vary with tree size in different ways that are not consistent with a universal shift towards a lower 'return on investment' strategy. Instead, species traits vary with size in patterns that likely reflect complex variation in water, light, nitrogen and carbon availability, storage and use.

Recent work has identified a worldwide

Lianas are an important component of neotropical forests, where evidence suggests that they are increasing in abundance and biomass. Lianas are especially abundant in seasonally dry tropical forests, and as such it has been hypothesized that they are better adapted to drought, or that they are at an advantage under the higher light conditions in these forests. However, the physiological and morphological characteristics that allow lianas to capitalize more on seasonal forest conditions compared to trees are poorly understood. Here, we evaluate how saplings of 21 tree and liana species from a seasonal tropical forest in Panama differ in cavitation resistance (P50) and maximum hydraulic conductivity (K(h)), and how saplings of 24 tree and liana species differ in four photosynthetic leaf traits (e.g., maximum assimilation and stomatal conductance) and six morphological leaf and stem traits (e.g., wood density, maximum vessel length, and specific leaf area). At the sapling stage, lianas had a lower cavitation resistance than trees, implying lower drought tolerance, and they tended to have a higher potential hydraulic conductivity. In contrast to studies focusing on adult trees and lianas, we found no clear differences in morphological and photosynthetic traits between the life forms. Possibly, lianas and trees are functionally different at later ontogenetic stages, with lianas having deeper root systems than trees, or experience their main growth advantage during wet periods, when they are less vulnerable to cavitation and can achieve high conductivity. This study shows, however, that the hydraulic characteristics and functional traits that we examined do not explain differences in liana and tree distributions in seasonal forests.

Many facets of plant form and function are reflected in general cross-taxa scaling relationships. Metabolic scaling theory (MST) and the leaf economics spectrum (LES) have each proposed unifying frameworks and organisational principles to understand the origin of botanical diversity. Here, we test the evolutionary assumptions of MST and the LES using a cross of two genetic variants of Arabidopsis thaliana. We show that there is enough genetic variation to generate a large fraction of variation in the LES and MST scaling functions. The progeny sharing the parental, naturally occurring, allelic combinations at two pleiotropic genes exhibited the theorised optimum (3/4) allometric scaling of growth rate and intermediate leaf economics. Our findings: (1) imply that a few pleiotropic genes underlie many plant functional traits and life histories; (2) unify MST and LES within a common genetic framework and (3) suggest that observed intermediate size and longevity in natural populations originate from stabilising selection to optimise physiological trade-offs.

The tissue traits and architectures of plant species are important for land-plant ecology in two ways. First, they control ecosystem processes and define habitat and resources for other taxa; thus, they are a high priority for understanding the ecosystem at a site. Second, knowledge of trait costs and benefits offers the most promising path to understanding how vegetation properties change along physical geography gradients. There exists an informal shortlist of plant traits that are thought to be most informative. Here, we summarize recent research on correlations and tradeoffs surrounding some traits that are prospects for the shortlist. By extending the list and by developing better models for how traits influence species distributions and interactions, a strong foundation of basic ecology can be established, with many practical applications.

Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional type or biome. Categories along the spectrum would, in general, describe leaf economic variation at the global scale better than plant functional types, because functional types overlap substantially in their leaf traits. Overall, modulation of leaf traits and trait relationships by climate is surprisingly modest, although some striking and significant patterns can be seen. Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate.

Warming, watering and elevated atmospheric CO(2)-concentration effects have been extensively studied separately; however, their combined impact on plants is not well understood. In the current research, we examined plant growth and physiological responses of three dominant species from the Eurasian Steppe with different functional traits to a combination of elevated CO(2), high temperature, and four simulated precipitation patterns. Elevated CO(2) stimulated plant growth by 10.8-41.7 % for a C(3) leguminous shrub, Caragana microphylla, and by 33.2-52.3 % for a C(3) grass, Stipa grandis, across all temperature and watering treatments. Elevated CO(2), however, did not affect plant biomass of a C(4) grass, Cleistogenes squarrosa, under normal or increased precipitation, whereas a 20.0-69.7 % stimulation of growth occurred with elevated CO(2) under drought conditions. Plant growth was enhanced in the C(3) shrub and the C(4) grass by warming under normal precipitation, but declined drastically with severe drought. The effects of elevated CO(2) on leaf traits, biomass allocation and photosynthetic potential were remarkably species-dependent. Suppression of photosynthetic activity, and enhancement of cell peroxidation by a combination of warming and severe drought, were partly alleviated by elevated CO(2). The relationships between plant functional traits and physiological activities and their responses to climate change were discussed. The present results suggested that the response to CO(2) enrichment may strongly depend on the response of specific species under varying patterns of precipitation, with or without warming, highlighting that individual species and multifactor dependencies must be considered in a projection of terrestrial ecosystem response to climatic change.

Terrestrial net primary production (NPP) quantifies the amount of atmospheric carbon fixed by plants and accumulated as biomass. Previous studies have shown that climate constraints were relaxing with increasing temperature and solar radiation, allowing an upward trend in NPP from 1982 through 1999. The past decade (2000 to 2009) has been the warmest since instrumental measurements began, which could imply continued increases in NPP; however, our estimates suggest a reduction in the global NPP of 0.55 petagrams of carbon. Large-scale droughts have reduced regional NPP, and a drying trend in the Southern Hemisphere has decreased NPP in that area, counteracting the increased NPP over the Northern Hemisphere. A continued decline in NPP would not only weaken the terrestrial carbon sink, but it would also intensify future competition between food demand and proposed biofuel production.

Lianas are an important component of tropical forests and often abundant in open habitats, such as tree-fall gaps, forest edges, and disturbed forests. The abundance of lianas in tropical forests has been increasing as a result of global environmental change and increasing forest fragmentation. In order to understand this phenomenon in terms of leaf functional traits and to evaluate their competitive potential, we conducted a cost-benefit analysis of leaves from 18 liana species and 19 tree species in a tropical seasonal rain forest. The results revealed that lianas were scattered in a group distinct from trees along the first axis of a principal component analysis using 15 leaf ecophysiological traits, being located at the quick-return end of the leaf economics spectrum, with higher specific leaf area and photosynthetic rates (A), higher photosynthetic nitrogen (N) and phosphorus (P) use efficiencies, a lower leaf construction cost per unit leaf area (CC) and cost-benefit ratio (CC/A), and a shorter leaf life span (LLS). Trees showed the opposite trends. The results indicate that lianas can grow faster and capture resources more efficiently than trees in disturbed, open habitats. The positive relationship between LLS and CC/A revealed a trade-off between leaf construction cost and benefit over time. The 37 species analyzed had a mean foliar N/P ratio of 20, indicating that the forest was characterized by a P deficit. With an increasing atmospheric CO(2) concentration, the higher nutrient use efficiency could benefit lianas more than trees in terms of productivity, possibly also contributing to the increasing abundance of lianas in nutrient-limited tropical forests.