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Extreme precipitation events are becoming more intense and frequent due to climate change. This climatic shift is impacting the structure and dynamics of natural communities and the key ecosystem services they provide. Changes in species abundance under these conditions are thought to be mediated by functional traits, morpho‐physiological characteristics of an organism that impact its fitness. Future environmental conditions may, therefore, favour different traits to those in present‐day communities.After 6 years of manipulated precipitation levels, including drought (−50% of ambient precipitation), irrigation (+50% of ambient precipitation), and control (ambient precipitation), we measured five key functional traits (plant height, leaf dry matter content [LDMC], leaf thickness, specific leaf area [SLA], and leaf phosphorus concentration) in 586 individual vascular plants to study the effects of precipitation changes on community‐weighted functional traits. Additionally, we tested whether the precipitation change effects on the traits depend on the time of the growing season.As expected, reduced precipitation impacted community composition only for the late‐season timing, after the seasonal field mowing, but led to a significant change in all community‐level plant traits between season timings. Under drought, communities shifted towards shorter individuals with thicker but small leaves and lower phosphorous content. Overall, a combination of community reassembly and intraspecific variation contributed to community‐weighted differences between control and drought plots for plant height, SLA, and LDMC traits. Species turnover was the main driver of community‐weighted means (CWMs) shifts in all traits in the late‐season but SLA. Whereas all traits showed variations at the community level with drought, SLA and LDMC were the most responsive traits at the species level. Nevertheless, our results suggest underestimation of intraspecific variation due to sensitive species lower abundance under stress. No differences in CWMs of functional traits were observed between control and irrigated plots.Synthesis: Our findings suggest that functional trait composition of grassland communities may shift under climate change‐induced drought, depending on the growing season timings. Trait‐based attempts to predict ecosystem functioning must account for such temporal variation in community trait values. [ABSTRACT FROM AUTHOR]

Leaf area varies within and between species, and previous work has linked this variation to environment and evolutionary history. However, many previous studies fail to examine both these factors and often are data‐limited.To address this, our study developed a new workflow using machine learning to automate the extraction of leaf area from herbarium collections of Australian eucalypts (Eucalyptus, Angophora and Corymbia). This dataset included 136,599 measurements, expanding existing data on this taxon's leaf area by roughly 50‐fold. Our methods were validated using field standard metrics of accuracy, and comparisons to manual measurements both from the present study and existing datasets.With this dataset for the eucalypt clade, we observed positive relationships between leaf area and mean annual temperature and precipitation similar to those reported for the global flora. However, these relationships were not consistently observed within species, potentially due to gene flow suppressing local adaptation. When we examined these relationships at different phylogenetic levels, the slope of trait–climate associations within lineages converged towards the overall eucalypt slope at shallow phylogenetic scales (5–12 MY), suggesting that effects of gene flow relax just above the species level.The strengthening of trait–climate correlations at evolutionary scales just beyond the intraspecific level may represent a widespread phenomenon across various traits and taxa. Future studies can unveil these relationships with the larger sample sizes of new trait datasets generated through machine learning.Synthesis. Using machine learning, researchers are able to confirm current positive global relationships between leaf area and mean annual temperature and precipitation. Additionally, they were able to take this a step further and examine how it changes across time. Here they saw that at roughly 5–12 million years ago in the phylogenetic tree, the trait–climate slope begins to show significantly less variation. Overall, the study shows the potential of machine learning in ecology, with exciting new potential findings with its use. [ABSTRACT FROM AUTHOR]

Plant taxa and traits do not necessarily show synchronous responses to ecological disturbance. Based on the observation that taxonomically over‐diversified communities might be phenotypically redundant, we speculated that taxonomic and phenotypic community reassembly might be decoupled after fire in Mediterranean ecosystems.We applied a multi‐trait approach to describe plant community re‐assembly after fire across three 20‐year chronosequences based on 117 species and 23 traits, including whole‐plant, above‐ground and below‐ground traits. We quantified the post‐fire trajectories of different plant traits by analysing their community‐weighted means individually. We estimated the short‐ and long‐term phenotypic diversity of burned plots based on sets of traits. We also tested if trait and species turnover are decoupled across post‐fire trajectories. Finally, we calculated phenotypic redundancy, and assessed if above‐ and below‐ground traits have contrasted responses during post‐fire community reassembly.Individually, 16 out of 23 traits were affected by fire in the short term. Plant phenotypic diversity (stdMPD) decreased immediately after fire, driven by changes in whole‐ and above‐ground traits. Both whole‐ and above‐ground stdMPD in burned plots described positive trajectories across the chronosequences tending to converge with long‐unburned plots, whereas below‐ground stdMPD remained unaltered through time.Taxonomic and phenotypic beta diversity showed decoupled trajectories due to a larger species than trait replacement across time since fire. Finally, overall phenotypic redundancy of the studied plant communities described a regressive trajectory, similarly to above‐ground traits, whereas root traits kept a steady phenotypic redundancy through time.Synthesis. We provide evidence that above‐ and below‐ground traits describe different recovery trajectories after fire, with significant effects on the phenotypic redundancy of plant communities. Our results encourage the use of multi‐trait approaches to understand how the plant reassembly operates after disturbance, in order to refine ecological theory. This strategy might improve the efficacy of restoration programs through a functional approach to species selection. [ABSTRACT FROM AUTHOR]

Although disturbance is considered a major driver of plant invasions across many systems, our understanding of the mechanisms by which disturbance mediates understorey invasions in natural forests is limited.We used a national natural forest inventory dataset spanning New Zealand's wide climatic and soil fertility gradients to disentangle disturbance‐mediated community characteristics driving abundance, species richness and functional composition of understorey plant invasions.Disturbance‐mediated declines in canopy tree abundance and increases in soil fertility and pH increased non‐native plant richness and cover relative to co‐occurring native plant assemblages. Cover of non‐native species also increased with proximity to anthropogenic land cover.Non‐native plant assemblages had higher community‐weighted mean (CWM) values for specific leaf area (SLA) but lower CWM values for height and woodiness relative to native assemblages irrespective of disturbance. However, greater nearby anthropogenic land cover drove increased woodiness in non‐native assemblages but decreased woodiness in co‐occurring native assemblages.Synthesis: Our study provides the first national‐scale evidence that canopy disturbance effects on soil properties increase both richness and abundance of non‐native plants in natural forest understories. We also revealed functional trait differences between native and non‐native assemblages (SLA in particular), which could alter fundamental forest ecosystem processes like litter decomposition and nutrient cycling. Finally, landscape‐scale anthropogenic impacts may exacerbate forest invasions by increasing non‐native abundance and favouring woody invaders, which may achieve dominance in future forest communities over the longer‐term. [ABSTRACT FROM AUTHOR]

Phenotypic differences among populations stem from the interaction between neutral and adaptive processes, and phenotypic plasticity. Although clinal trait variation along climatic gradients often evolves in widely distributed species, it is unknown whether substrate specialization, such as that of Mediterranean gypsum plants, has constrained adaptation to climate.Using a common garden experiment with two contrasting watering treatments, we quantified phenotypic plasticity, assessed evidence for footprints of selection using FST – QST comparisons, and evaluated the ecological factors driving genetically based phenotypic differentiation of 11 populations encompassing the full environmental range of the gypsum shrub Lepidium subulatum.We found evidence for genetic differentiation among populations related to climatic differences, with populations from warmer and drier sites showing lower specific leaf area and leaf N, earlier phenology, greater water use efficiency and greater fitness. Multiple lines of evidence suggest that this differentiation was driven by past divergent selection rather than neutral processes. All populations showed high phenotypic plasticity, indicating that plasticity has not been selected against, even in populations from sites with harsher climatic conditions.Synthesis. Our results indicate that despite strong substrate specialization, adaptive differentiation related to climatic gradients occurs in this species. However, we also found that populations from mesic sites may be particularly vulnerable to future climate change given their relatively lower fitness under both wet and dry conditions. [ABSTRACT FROM AUTHOR]

Cover image: Illustrated here is the first part of an automated process to extract leaf area from herbarium images. Here the model's predictions of leaves are on the pressed plant specimen of Corymbia gilbertensis. Sheet ID NSW370638, collected in 1992 in Queensland, Australia. National Herbarium of NSW, https://registry.opendata.aws/nsw-herbarium ‐ Creative Commons BY 4.0 (CC‐BY 4.0). For full details see pages 2183‐2197.. [Extracted from the article]

Intraspecific trait variation can influence plant performance in different environments and may thereby determine the ability of individual plants to respond to climate change. However, our understanding of its patterns and environmental drivers across different spatial scales is incomplete, especially in understudied regions like the Arctic.To fill this knowledge gap, we examined above‐ground and below‐ground traits from three shrub taxa expanding across the tundra biome and evaluated their relationships with multiple microenvironmental and macroclimatic factors. The traits reflected plant size and structure (plant height, leaf area and root to shoot ratio), leaf economics (specific leaf area, nitrogen content), and root economics and collaboration with mycorrhizal fungi (specific root length, root tissue density, nitrogen content, and ectomycorrhizal colonisation intensity). We also measured leaf and root δ15N and leaf δ13C to characterise nitrogen source and acquisition pathways and plant water stress. Traits were measured in replicated plots (N = 135) varying in soil microclimate, thaw depth and organic layer thickness established across five sites spanning a macroclimate gradient in northern Alaska. This hierarchical design allowed us to disentangle the independent and combined effects of fine‐scale and broad‐scale factors on intraspecific trait variation.We found substantial intraspecific variation at fine spatial scales for most traits and less variation along the macroclimate gradient and between shrub taxa. Consistent with these patterns, microenvironmental factors, mainly soil moisture and thaw depth, interacted with macroclimate, mainly climatic water deficit, to structure size‐structural and leaf trait variation. In contrast, most root traits responded additively to thaw depth and macroclimate.Synthesis. Our results demonstrate that above‐ground and below‐ground tundra shrub traits respond differently to microenvironmental and macroclimatic variation. These differing responses contribute to substantial trait variation at fine spatial scales and may decouple above‐ground and below‐ground trait responses to climate change. [ABSTRACT FROM AUTHOR]

Secondary metabolites play an important role in plant adaptation, because they can mitigate biotic and abiotic environmental stresses. However, their production and allocation incur different costs and benefits, and are therefore subject to trade‐offs, which are less studied.To understand large‐scale geographic patterns of secondary metabolites, and their environmental drivers and trade‐offs, we studied 39 natural populations of the perennial herb Japanese knotweed (Reynoutria japonica) along a large latitudinal gradient in China. We measured the concentrations of six polyphenols in leaves and rhizomes of R. japonica, and associated the variation in these metabolites with biotic and abiotic environmental factors as well as with functional plant traits and putative costs of secondary metabolites.We found that climate was an important driver of variation in secondary metabolites, both above‐ and below‐ground. Remarkably, the patterns of association differed between leaves and rhizomes, as well as between putative low‐cost versus high‐cost compounds. While annual mean temperature was a stronger predictor of above‐ground metabolites, annual precipitation was more frequently associated with variation in below‐ground metabolites. Moreover, annual temperature was positively associated with high‐cost metabolites, but negatively with low‐cost metabolites. Above‐ground secondary metabolites were generally more strongly associated with functional traits (e.g. specific leaf area) than below‐ground metabolites, and in all cases the directions of correlation were opposite for low‐cost versus high‐cost metabolites above‐ground. The patterns of association also varied with latitude such that leaf concentrations of low‐cost metabolites (quercetin) increased but those of high‐cost metabolites (resveratrol, piceid and emodin) decreased at higher latitudes. In rhizomes, in contrast, the concentrations of high‐cost metabolites (piceid and emodin) increased with latitude.Synthesis. Our findings indicate that allocation strategies differ between above‐ and below‐ground tissues of Reynoutria japonica. As latitude increases, R. japonica invests relatively more into below‐ground metabolites. We propose that reduced high‐cost metabolites in the leaves at higher latitudes may help to conserve nutrients after defoliation, while maintaining high‐cost metabolites in rhizomes may be important for persistent allelopathic effects and resource conservation below‐ground. The divergent patterns of above‐ and below‐ground metabolite allocation thus likely reflect the multiple functions of metabolites and the plants' adaptation to different environments. [ABSTRACT FROM AUTHOR]

During primary succession, the abundance of different species and their associated plant traits change over time. Understanding how plant traits linked to colonising and competitive abilities change through succession is important for determining whether community assembly can be predicted. Examining this across more than one taxon group can reveal if these patterns are generalisable.Here, we investigated primary succession on bare chalk for a chronosequence spanning 33 years for two different taxa, vascular plants and bryophytes. We examined how abundance changed through succession, and how this related to species' colonising and competitive abilities, using relevant plant traits for each taxa. A zero‐inflated beta regression model was used to investigate the effects of traits on both presence/absence and abundance‐when‐present of vascular plants and bryophytes.Vascular plants with a larger specific leaf area were more likely to occur later in succession. Vascular plants, which were hemicryptophytes, wind dispersing and had a lower canopy height, were more likely to increase in abundance‐when‐present during succession.Bryophytes with a larger spore diameter were more likely to occur later in succession. Shorter bryophytes with a greater frequency of sporophyte production had a higher abundance early in succession, representing their high colonising abilities. Whereas later in succession larger bryophytes, with a mat or weft life form and low sporophyte frequency were more abundant, indicating a shift towards greater competitive abilities.Synthesis. This study has revealed different patterns for vascular plants and bryophytes regarding colonisation and changes in abundance through succession, and the associated traits linked to colonising and competitive abilities. Although some traits were found to influence abundance through succession for vascular plants, these were often contrary to the expected pattern representing the change from colonising to competitive abilities, whereas for bryophytes, there was more evidence for this shift with successional age. This suggests that general theories on succession‐linked plant traits should not be relied upon in isolation for the prediction of community assembly. Context, particularly successional age in relation to the available species pool is also key. [ABSTRACT FROM AUTHOR]

Studies of drivers shaping forest communities frequently include abiotic or biotic factors, while their interactive effects remain understudied. Here, we combined data on two prominent abiotic gradients, climatic moisture deficit and wildfire probability, along with tree functional neighbourhoods (i.e. trait differences of close neighbours) to assess variation in survival and growth of 56 tree species in the northwestern US.We asked two questions: (1) How does functional neighbourhood dissimilarity vary with environmental gradients? and (2) How do demographic rates of tree species in the northwestern United States vary with the interactive effects of environmental gradients and functional neighbourhood? We expected functional neighbourhoods to become more similar as environmental stress increased, due to a convergence of species towards an optimum stress tolerance strategy. We also predicted the interactive effects of abiotic and biotic factors on tree demography and high variation in species‐specific responses to these interactive effects due to divergent species life history strategies.Functional neighbourhoods defined by dissimilarities in stem conductivity, litter decomposition, resprouting ability and specific leaf area changed with climate, shifting to more diverse neighbourhoods as climatic moisture deficit and wildfire probability increased. Results supported interactive effects of the functional neighbourhood and climatic moisture deficit or wildfire probability on tree demography, but only when the identity of dominant species was considered. Species‐specific responses were highly variable in their direction and magnitude and often demonstrated opposing effects of climate and the functional neighbourhood and climatic moisture deficit on tree demography.Synthesis. Our findings show that climate and tree neighbourhood functional dissimilarity jointly impact tree demography; however, the effects are species‐specific. Results of this study highlight the need to consider the interactive effects of abiotic and biotic contexts and individual species responses to their environment to adequately understand tree persistence under current and future climate conditions. [ABSTRACT FROM AUTHOR]

A central goal at the interface of ecology and conservation is understanding how the relationship between biodiversity and ecosystem function (B–EF) will shift with changing climate. Despite recent theoretical advances, studies which examine temporal variation in the functional traits and mechanisms (mass ratio effects and niche complementarity effects) that underpin the B–EF relationship are lacking.Here, we use 13 years of data on plant species composition, plant traits, local‐scale abiotic variables, above‐ground net primary productivity (ANPP), and climate from the alpine tundra of Colorado (USA) to investigate temporal dynamics in the B–EF relationship. To assess how changing climatic conditions may alter the B–EF relationship, we built structural equation models (SEMs) for 11 traits across 13 years and evaluated the power of different trait SEMs to predict ANPP, as well as the relative contributions of mass ratio effects (community‐weighted mean trait values; CWM), niche complementarity effects (functional dispersion; FDis) and local abiotic variables. Additionally, we coupled linear mixed effects models with Multimodel inference methods to assess how inclusion of trait–climate interactions might improve our ability to predict ANPP through time.In every year, at least one SEM exhibited good fit, explaining between 19.6% and 57.2% of the variation in ANPP. However, the identity of the trait which best explained ANPP changed depending on winter precipitation, with leaf area, plant height and foliar nitrogen isotope content (δ15N) SEMs performing best in high, middle and low precipitation years, respectively. Regardless of trait identity, CWMs exerted a stronger influence on ANPP than FDis and total biotic effects were always greater than total abiotic effects. Multimodel inference reinforced the results of SEM analysis, with the inclusion of climate–trait interactions marginally improving our ability to predict ANPP through time.Synthesis. Our results suggest that temporal variation in climatic conditions influences which traits, mechanisms and abiotic variables were most responsible for driving the B–EF relationship. Importantly, our findings suggest that future research should consider temporal variability in the B–EF relationship, particularly how the predictive power of individual functional traits and abiotic variables may fluctuate as conditions shift due to climate change. [ABSTRACT FROM AUTHOR]

Top‐down and bottom‐up forces in tropical savannas have shaped the evolution of traits that enable plants to thrive in environments where soils are poor, dry seasons are long, fire is frequent, woody plants and grasses compete and herbivores range from cryptic caterpillars to elephants that topple entire trees.African savannas and the South American cerrado have similar climates and fire regimes, but differ in the presence of large mammal herbivores, which are mostly extinct in the cerrado. These biomes offer an instructive comparison to understand how plant defence traits evolved in response to differential herbivore pressure. Within Africa, mammalian herbivore pressure also differs across savannas, being lower in the miombo relative to more open, mixed savannas.The dominance of specialist insect herbivores in the cerrado, relative to the more generalist mammalian herbivores in Africa, suggests that defence traits will differ between savannas in accordance with herbivore identity and pressure.Wood is densest in mixed African savannas, as expected because large mammals often damage trees. Specific leaf area, related to palatability, is higher in mixed African savannas and the cerrado relative to the miombo, while leaf N is surprisingly higher in miombo species. Ant mutualists are important defences in mixed African savannas and the cerrado.Defensive chemistry has received less attention in the trait literature. Foliar phenolics, the most commonly studied chemical defences in savannas, vary in their efficacy. New analyses isolating specific compounds are informative as is the evaluation of phytochemical diversity as a defence. There are indications that phytochemical defences are more diverse in the cerrado, which may be related to greater specialization of cerrado herbivores.Synthesis. The dominance of specialist insect herbivores in the cerrado, relative to generalist mammalian herbivores in Africa, selected for different plant defence traits, contributing to the separation of species along the leaf economics spectrum and demonstrating the importance of plant defences as plant functional traits. African savanna species seem to follow a more acquisitive strategy, followed by miombo species. Cerrado species appear to follow a more conservative strategy with greater investments in tough leaves and chemical defences. [ABSTRACT FROM AUTHOR]

The plant economics spectrum (PES) drives nutrient cycling through effects on soil decomposers. However, dead phytomass may remain standing or unshed (marcescent), hardly accessible to decomposers and be photodegraded. In arid zones, the significant part of marcescent phytomass can be decomposed without touching the ground. In temperate zones, photodegradation of marcescent phytomass is low but prompts important chemical changes, which affect its subsequent decomposability in the soil and alters the surrounding environment. It is unknown, however, how common marcescence is among different taxa and in which habitats, and how it is coordinated by PES traits.We sampled standing (marcescent) and lying (shed) dead phytomass from a broad spectrum of 127 herbaceous temperate species in a common garden experiment and related these parameters to PES traits, species ecological preferences and phylogeny.Nearly all species (97%) kept their phytomass marcescent. Tall species with a small leaf area and high leaf carbon had a high level of marcescence. Marcescent species also preferred sites affected by severe (but not necessarily frequent) disturbance. The degree of marcescence was considerably conserved in phylogeny.Synthesis. Marcescence extends PES trait effects on ecosystems, particularly in immature habitats, being a common but overlooked phenomenon of the temperate flora. [ABSTRACT FROM AUTHOR]

Widespread forest loss and fragmentation dramatically increases the proportion of forest areas located close to edges. Although detrimental, the precise extent and mechanisms by which edge proximity impacts remnant forests remain to be ascertained.By combining unmanned aerial vehicle laser scanning (UAV‐LS) with field data from 46 plots distributed at varying distances from the edge to the forest interior in a fragmented forest of New‐Caledonia, we investigated edge influence on forest structure, composition, function, above‐ground biomass (AGB) and microclimate. Using simple linear regressions, structural equation modelling and variance partitioning, we analysed the direct and indirect relationships between distance to edge, UAV‐LS‐derived canopy structural metrics, understorey microclimate, AGB, taxonomic and functional composition while accounting for the potential influence of fine‐scale variation in topography.We found that the distance to the closest forest edge was strongly correlated with canopy structure and that canopy structure was better correlated to forest composition, function, biomass and microclimate than distance to the closest forest edge. This suggests that the influence of edge is mediated by changes in canopy structure. Plots located near the edge exhibited a lower canopy with more gaps, higher microclimate extremes, lower biomass, lower taxonomic and functional diversity as well as denser wood and lower specific leaf area. UAV‐LS‐derived canopy structural metrics were relevant predictors of understorey microclimate, biomass and taxonomic and functional composition. Overall, the influence of topography was marginal compared to edge effects.Synthesis. Accounting for fine‐scale variation in canopy structure captured by UAV‐LS provides insights on the multiple edge impacts on key forest properties related to structure, diversity, function, biomass and microenvironmental conditions. Integrating UAV‐LS‐derived data can foster our understanding of cascading and interacting impacts of anthropogenic influence on tropical forest ecosystems and should help to improve conservation strategies and landscape management policies. [ABSTRACT FROM AUTHOR]

Grasslands are expected to experience droughts of unprecedented frequency and magnitude in the future. Characterizing grassland responses and recovery from drought is therefore critical to predict the vulnerability of grassland ecosystems to climate change. Most previous studies have focused on ecosystem responses during drought while investigations of post‐drought recovery are rare. Few studies have used functional traits, and in particular bud or clonal traits, to explore the mechanisms underlying grassland responses to and recovery from drought.To address this issue, we experimentally imposed a four‐year drought in a C3‐dominated grassland in northeastern China and monitored recovery for 3 years post‐drought. We investigated the immediate and legacy effects of drought on total above‐ground net primary productivity (ANPP), ANPP of functional groups (rhizomatous grasses, bunch grasses and forbs), and how the legacy effects were driven by plant species diversity, clonal traits and vegetative traits.We found that drought progressively reduced total ANPP over the 4‐year period. The reductions in total ANPP in the first and third drought years were caused by the decrease in ANPP of bunch grasses only, while that of the second year was caused by declines in ANPP of bunch grasses and forbs, and the fourth year decline was linked to all three functional groups. The post‐drought recovery of ANPP, which occurred despite the continued loss of plant species diversity, was mainly driven by rapid recovery of rhizomatous and bunch grasses, which compensated for the slow response by forbs. The rapid post‐drought recovery of these grasses can be attributed to their relatively large, intact bud and shoot densities post‐drought, as well as the recovery of plant height and specific leaf area. The rapid recovery of grasses possibly restricted the growth and distribution of forbs, resulting in reduced forb ANPP and, consequently, lower species diversity during the recovery period.Synthesis. These results highlight the potential for positive legacy effects of drought on ANPP as well as the important and complementary roles of plant reproductive and vegetative traits in mediating ecosystem recovery from drought in a C3‐dominated grassland. [ABSTRACT FROM AUTHOR]

Foliar fungal pathogens can substantially reduce plant biomass. This effect can be modulated by environment conditions, such as soil nitrogen availability and air temperature. The ongoing global changes are altering these variables and thus interact with pathogens to influence plant biomass, but experimental test of their interactions is scarce.We conducted a 4‐year field experiment in a Tibetan alpine meadow to examine the interactive effects of nitrogen addition, warming and foliar pathogens (via fungicide application) on plant biomass. We also measured plant functional traits, species richness and abundance to test the possible mechanisms underlying these interactions.Our results showed that foliar fungal pathogens reduced plant community biomass under nitrogen addition, which in turn weakened the positive nitrogen effect on community biomass. Mechanistically, nitrogen addition shifted the plant communities towards fast‐growing traits; this happened predominantly because of changes in within‐species trait values, including an increase in specific leaf area and height. These trait changes resulted in greater suppression of plant biomass by pathogens, likely because of the trade‐offs associated with the allocation of resources to plant growth and defense. Moreover, the reduction in species richness amplified the pathogen effect under nitrogen addition due to the increased density and susceptibility of the most dominant species (i.e. Kobresia capillifolia). Furthermore, warming did not interact with pathogens and nitrogen addition to influence plant community biomass, but their three‐way interaction modified the biomass of K. capillifolia. Specifically, warming enhanced the positive effect of nitrogen addition on the biomass of K. capillifolia in the fungicide, low infection plots, while it weakened the nitrogen effect in the no fungicide, high infection plots.Synthesis. Our results demonstrate how pathogens interact with nitrogen addition and warming to influence the biomass of dominant species and the whole plant community. Our study highlights the importance of considering foliar fungal pathogens when assessing ecosystem responses to multiple global change factors. [ABSTRACT FROM AUTHOR]

1. Lianas account for a small fraction of forest biomass, but their contribution to leaf or litter biomass and thus to food webs can be substantial. Globally liana exhibit fast life-history traits. Thus, liana litter may decompose faster than tree litter, and could enhance the decomposition of tree litter (complementarity effect). The differences in decomposition may also vary with mesofauna access or across forest communities. The contribution of these factors to nutrient biogeochemical cycling is poorly understood. 2. We examined the decomposition of litter of 20 liana and 20 tree species of three different tropical forest communities in southern China, over 1 year. (i) We incubated the litter in bags with coarse and fine mesh to distinguish mesofaunal and microfaunal effects. (ii) We used single-species litter bags to compare decomposition rates of lianas and trees, to test which functional traits best explained decomposition, and whether those traits differed between lianas and trees, and among forest types. (iv) We used mixed-species litter bags to test whether liana litter enhances decomposition in litter mixtures. (v) We evaluated how leaf litter nutrients decayed in relation to litter mass. 3. Litter decayed faster in coarse-mesh than fine-mesh bags, but there was no interaction effect with forest type or growth form. Liana litter decayed faster than tree litter in single-species bags with mesofauna access and in mixed bags (liana-only mix, tree-only mix) without mesofauna. Lianas had higher nitrogen content and specific leaf area and lower leaf dry matter content (LDMC) and toughness than trees. Decomposition rate was significantly negatively related to LDMC. Litter of evergreen broadleaved forest decomposed slower than that of other forest types. Liana litter did not enhance the decomposition of tree litter in mixtures. Liana litter released calcium slightly faster than trees. 4. Synthesis: Leaf litter decomposes faster for lianas than trees, despite high variability of traits and decomposition rates within each growth form and overlap between growth forms, and we found no evidence for the complementarity hypothesis. Our study sheds light on the potential role of lianas within brown food webs and their importance on terrestrial biogeochemistry. [ABSTRACT FROM AUTHOR]

1. Tree survival affects forest biodiversity, structure and functioning. However, little is known about feedback effects of biodiversity on survival and its dependence on functional traits and interannual climatic variability. 2. With an individual-based dataset from a large subtropical forest biodiversity experiment, we evaluated how species richness, functional traits and time-dependent covariates affected annual tree survival rates from age 3–12 (years) after planting 39 species across a diversity gradient from 1 to 2, 4, 8 and 16 tree species. 3. We found that overall survival rates marginally increased with diversity at the plot level, with large variation among plots within diversity levels. Significant variation among species in survival responses to diversity and changes in these responses with age were related to species functional traits and climatic conditions. Generally, survival rates of conservative species (evergreen, late-successional species with thick leaves and high carbon to nitrogen ratio but low specific leaf area, leaf phosphorus and hydraulic conductivity) increased with diversity, age and yearly precipitation, whereas acquisitive species showed opposite responses. 4. Synthesis. Our results indicate that interactions between diversity, species functional traits and yearly climatic conditions can balance survival among species in diverse forests. Planting mixtures of species that differ in functional traits in afforestation projects may lead to a positive feedback loop where biodiversity maintains biodiversity, together with its previously reported beneficial effects on ecosystem functioning. [ABSTRACT FROM AUTHOR]

Consumer‐resource interactions are often influenced by other species in the community, such as when neighbouring plants increase or reduce herbivory to a focal plant species (known as associational effects). The many studies on associational effects between a focal plant and some neighbour have shown that these effects can vary greatly in strength and direction. But because almost all of these studies measure associational effects from only one or two neighbour species, we know little about the actual range of associational effects that a plant species might encounter in a natural setting. This makes it difficult to determine how important effects of neighbours are in real field settings, and how associational effects might interact with competition and other processes to influence plant community composition.In this study, we used a field experiment with a focal species, Solanum carolinense, and 11 common neighbour species to investigate how associational effects vary among many co‐occurring neighbour species and to test whether factors such as neighbour plant apparency, phylogenetic proximity to the focal species, or effects on focal plant defence traits help to explain interspecific variation in associational effect strength.We found that some neighbour species affected S. carolinense damage and attack by specialist herbivores, but associational effects of most neighbours were weak. Associational effects increased herbivore attack on average earlier in the season (associational susceptibility) and reduced herbivore attack on average later in the season (associational resistance) relative to S. carolinense in monoculture.We found some evidence that a neighbour's associational effect was related to its biomass and phylogenetic proximity to the focal species. While neighbour species differed in their effects on physical leaf traits of focal plants (trichome density, specific leaf area, and leaf toughness), these traits did not appear to mediate the effects of neighbours on focal plant herbivory.Synthesis. Our results suggest that the distribution of associational effect strengths in natural communities are similar to those observed for other interaction types, and that multiple mechanisms are likely acting simultaneously to shape associational effects of different neighbour species. [ABSTRACT FROM AUTHOR]

Intraspecific trait variability (ITV) provides the material for species' adaptation to environmental changes. To advance our understanding of how ITV can contribute to species' adaptation to a wide range of environmental conditions, we studied five widespread understorey forest species exposed to both continental‐scale climate gradients, and local soil and disturbance gradients. We investigated the environmental drivers of between‐site leaf and root trait variation, and tested whether higher between‐site ITV was associated with increased trait sensitivity to environmental variation (i.e. environmental fit).We measured morphological (specific leaf area: SLA, specific root length: SRL) and chemical traits (Leaf and Root N, P, K, Mg, Ca) of five forest understorey vascular plant species at 78 sites across Canada. A total of 261 species‐by‐site combinations spanning ~4300 km were sampled, capturing important abiotic and biotic environmental gradients (neighbourhood composition, canopy structure, soil conditions, climate). We used multivariate and univariate linear mixed models to identify drivers of ITV and test the association of between‐site ITV with environmental fit.Between‐site ITV of leaf traits was primarily driven by canopy structure and climate. Comparatively, environmental drivers explained only a small proportion of variability in root traits: these relationships were trait specific and included soil conditions (Root P), canopy structure (Root N) and neighbourhood composition (SRL, Root K). Between‐site ITV was associated with increased environmental fit only for a minority of traits, primarily in response to climate (SLA, Leaf N, SRL).Synthesis. By studying how ITV is structured along environmental gradients among species adapted to a wide range of conditions, we can begin to understand how individual species might respond to environmental change. Our results show that generalisable trait–environment relationships occur primarily aboveground, and only accounted for a small proportion of variability. For our group of species with broad ecological niches, variability in traits was only rarely associated with higher environmental fit, and primarily along climatic gradients. These results point to promising research avenues on the various ways in which trait variation can affect species' performance along different environmental gradients. [ABSTRACT FROM AUTHOR]

In flowering plants (angiosperms), the herbaceous habit has evolved repeatedly from the ancestral woody state and herbs evolved repeatedly back to woody plants. Yet, how common these transitions were and which ecological conditions promote the herbaceous habit is poorly known. Several hypotheses exist, postulating an advantage of the herbaceous growth form to better cope with frost, drought, fire and shade and in allowing a fast life strategy, but their evaluation has been hitherto limited and support equivocal. We aim to evaluate these hypotheses by testing the difference between woody plants and herbs for a set of variables related to these hypotheses.We compiled and integrated data for up to 21,581 species representing 359 families from public databases. We estimated the minimum number of evolutionary transitions between both growth forms. We assembled data on frost, drought, fire and shade tolerances, clonality and specific leaf area and we tested individual hypotheses by comparing herbaceous and woody angiosperm growth forms globally and within selected biomes and clades using phylogenetic comparative analyses.We found 1656 evolutionary transitions from woody towards herbaceous growth form and 2111 transitions in the opposite direction. In agreement with our expectations, herbs were more tolerant to frost and shade than woody plants and had higher specific leaf area. However, the growth forms did not differ in their fire tolerance and clonality. Furthermore, contrary to our expectation, woody plants were more drought tolerant than herbs. The majority of the differences were robust to the choice of biome or clade.Synthesis. Both herbaceous and woody habits evolved many times making the evolution of growth forms a well‐replicated event and suggesting that conditions favourable for either of the growth forms emerge often and plants respond to them. Apart from standard explanation by low temperatures, the success of herbs was likely enabled also by biotic interactions—by their fast life strategy, which is beneficial in seasonal and early successional habitats, and by their ability to tolerate shade. [ABSTRACT FROM AUTHOR]

Perennial herbaceous species form their above‐ground parts every year anew and discard them before the advent of winter. The senescence of above‐ground structures is thus an inevitable part of their life cycle. This is also a key process that determines photosynthetic gain late in the season and the economy of soil‐borne nutrients.Here we address patterns and drivers of the shoot senescence of perennial herbaceous plants. We present a comparative study of 231 temperate species, ranging from spring ephemeroids to species senescing in late autumn, in a common botanical garden collection. We assessed senescence by measuring size decline in the autumn part of the season.There were two main directions of variation in senescence trajectories: the pace–date axis, separating early and fast senescing species from late and slowly senescing species, and the shape‐asynchrony axis, separating species with accelerating and synchronised senescence from constant senescence asynchronous among individual shoots. While accelerating senescence late in the season can be due to passive effects of the environment (e.g. frost), accelerating senescence early in the season is likely to be an indication of an active process driven by the enzymatic activity of the plant.The pace and shape of shoot senescence were associated with both leaf‐ and shoot‐level traits. Species having leaves with high dry matter content senesced linearly and with higher asynchrony. Species with a larger specific leaf area senesced earlier and faster, while tall plants and plants with monocyclic shoots senesced later and in a more synchronous and accelerating manner.Species from different habitats varied in their senescence patterns. Forest species postpone their senescence relative to open‐habitat species, presumably to boost their photosynthetic balance. We did not confirm the hypothesis that plants from nutrient‐poor habitats senesce earlier to retain soil‐borne nutrients before the winter.Synthesis. Shoot senescence in herbaceous plants is a neglected phenomenon in its own right, which bears only superficial similarity to autumn leaf shedding in trees. Individual species differ strongly in the pace, shape and synchrony of their senescence trajectories, with a potential bearing on the carbon and nutrient dynamics of their habitats. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms underlying community stability has become an urgent need to protect ecosystems from global change and resulting biodiversity loss. While community stability can be influenced by species richness, synchrony in annual fluctuations of species, species stability and functional traits, the relative contributions of these drivers to stability are still unclear. In semi‐natural grasslands, land‐use changes such as fertilization might affect stability by decreasing richness and influencing year‐to‐year fluctuations. In addition, they can promote long‐term directional trends, shifting community composition and influencing grassland maintenance. Thus, it is important to consider how species and community stability vary year‐to‐year but also in the long term.Using a 14‐year vegetation time series of a species‐rich semi‐natural Mediterranean grassland, we studied the relative importance of richness, synchrony, species stability and functional traits on community stability. To assess land‐use change effects on stability, we applied a fertilization treatment. To distinguish stability patterns produced by year‐to‐year fluctuations from those caused by long‐term trends, we compared the results obtained using a detrending approach from those without detrending.Independently of the treatment and approach applied, the most stable communities were those composed of asynchronous species with low specific leaf area. Fertilization decreased year‐to‐year and long‐term community stability by increasing community‐weighted mean of specific leaf area, decreasing species stability or also reducing richness in the case of year‐to‐year stability. Additionally, traits such as seed mass had an indirect effect on stability through synchrony. Long‐term trends appeared in control and fertilized plots (due to fertilization), decreasing community and species stability and leading to differences in the relationships found between community stability and some of its drivers. This reflects the importance of accounting for the effect of temporal trends on community and species stability using both a long‐term and a year‐to‐year approach.Synthesis. Stability is influenced by richness, synchrony and functional traits. Fertilization decreases species and community stability by promoting long‐term trends in species composition, favouring competitive species and decreasing richness. Studying stability at the community level and species level, and accounting for the effect of trends is essential to understand stability and its drivers more comprehensively. [ABSTRACT FROM AUTHOR]

Climate warming is shifting the distributions of mountain plant species to higher elevations. Cold‐adapted plant species are under increasing pressure from novel competitors that are encroaching from lower elevations. Plant capacity to adjust to these pressures may be measurable as variation in trait values within a species. In particular, the strength and patterns of intraspecific trait variation along abiotic and biotic gradients can inform us whether and how species can adjust their anatomy and morphology to persist in a changing environment.Here, we tested whether species specialized to high elevations or with narrow elevational ranges show more conservative (i.e. less variable) trait responses across their elevational distribution, or in response to neighbours, than species from lower elevations or with wider elevational ranges. We did so by studying intraspecific trait variation of 66 species along 40 elevational gradients in four countries in both hemispheres. As an indication of potential neighbour interactions that could drive trait variation, we also analysed plant species' height ratio, its height relative to its nearest neighbour.Variation in alpine plant trait values over elevation differed depending on a species' median elevation and the breadth of its elevational range, with species with lower median elevations and larger elevational range sizes showing greater trait variation, i.e. a steeper slope in trait values, over their elevational distributions. These effects were evidenced by significant interactions between species' elevation and their elevational preference or range for several traits: vegetative height, generative height, specific leaf area and patch area. The height ratio of focal alpine species and their neighbours decreased in the lower part of their distribution because neighbours became relatively taller at lower elevations. In contrast, species with lower elevational optima maintained a similar height ratio with neighbours throughout their range.Synthesis. We provide evidence that species from lower elevations and those with larger range sizes show greater intraspecific trait variation, which may indicate a greater ability to respond to environmental changes. Also, larger trait variation of species from lower elevations may indicate stronger competitive ability of upslope shifting species, posing one further threat to species from higher ranges. [ABSTRACT FROM AUTHOR]

Plant functional traits can provide a mechanistic understanding of community responses to global change and of community effects on ecosystem functions. Nitrogen enrichment typically shifts trait composition by promoting the dominance of acquisitive plants (high specific leaf area [SLA] and low leaf dry matter content [LDMC]), translating into high biomass production. Changes in mean trait values can be due to shifts in species identity, relative abundances and/or intraspecific trait values. However, we do not know the relative importance of these shifts in determining trait responses to environmental changes, or trait effects on ecosystem functioning, such as biomass production.We quantified the relative importance of species composition, abundance and intraspecific shifts in driving variation in SLA and LDMC, and how these shifts affected above‐ and below‐ground biomass. We measured traits in a grassland experiment manipulating nitrogen fertilisation, plant species richness, foliar fungal pathogen removal and sown functional composition (slow vs. fast species). We fitted structural equation models to test the importance of abundance and intraspecific shifts in determining (a) responses of functional composition to treatments and (b) effects on above‐ and below‐ground biomass.We found that species intraspecific shifts were as important as abundance shifts in determining the overall change in functional composition (community weighted mean trait values), and even had large effects compared to substantial initial variation in sown trait composition. Intraspecific trait shifts resulted in convergence towards intermediate SLA in diverse communities; although convergence was reduced by nitrogen addition and enhanced by pathogen removal. In contrast, large intraspecific shifts in LDMC were not influenced by the treatments. However, despite large responses, intraspecific trait shifts had no effect on above‐ or below‐ground biomass. Only interspecific trait variation affected functioning: below‐ground biomass was reduced by SLA and increased by LDMC, while above‐ground biomass was increased by SLA.Synthesis. Our results add to a growing body of literature showing large intraspecific trait variation and emphasise the importance of using field collected data to determine community functional composition. However, they also show that intraspecific variation does not necessarily affect ecosystem functioning and therefore response–effect trait relationships may differ between versus within species. [ABSTRACT FROM AUTHOR]

Positive relationships between structural diversity and forest productivity have been documented in controlled experiments and early secondary forests, however, negative relationships have also been observed in late successional forests. The mechanisms causing observed relationships between structural diversity and productivity are not well‐established, but complementarity among crowns and asymmetric competition have been suggested.We used LiDAR and repeated census data to examine the relationship between canopy structural diversity and productivity in nine 1‐ha subtropical forest plots along a disturbance gradient in southeastern China. We quantified the relative importance of community composition, species diversity, canopy structural diversity, leaf area index (LAI) and disturbance regime on productivity using piecewise structural equation modelling. We also tested how vertical leaf area distribution affected productivity.Contrary to many prior observations, we found a negative relationship between canopy structural diversity and forest productivity. The negative effect may stem from asymmetric competition between overstorey and understorey leaves, leading to a lower leaf area efficiency (i.e. wood production per leaf area). Asymmetric competition was suggested by a negative relationship between understorey leaf area and total productivity. Changes in community composition over the disturbance gradient, but not species diversity, had a significant effect on productivity.Synthesis. Our study suggests that leaf area and canopy structural diversity have contrasting effects on productivity in this subtropical forest, and this needs to be considered when estimating rates of carbon sequestration in secondary forests. The negative effect of asymmetric competition on productivity is comparable to that of the shift in species composition over succession, highlighting the role of canopy structural diversity in shaping forest productivity. [ABSTRACT FROM AUTHOR]

1. Woody species' requirements and environmental sensitivity change from seedlings to adults, a process referred to as ontogenetic shift. Such shifts can be increased by climate change. To assess the changes in the difference of temperature experienced by seedlings and adults in the context of climate change, it is essential to have reliable climatic data over long periods that capture the thermal conditions experienced by the individuals throughout their life cycle. 2. Here we used a unique cross-European database of 2,195 pairs of resurveyed forest plots with a mean intercensus time interval of 37 years. We inferred macroclimatic temperature (free-air conditions above tree canopies--representative of the conditions experienced by adult trees) and microclimatic temperature (representative of the juvenile stage at the forest floor, inferred from the relationship between canopy cover, distance to the coast and below-canopy temperature) at both surveys. We then address the long-term, large-scale and multitaxa dynamics of the difference between the temperatures experienced by adults and juveniles of 25 temperate tree species. 3. We found significant, but species-specific, variations in the perceived temperature (calculated from presence/absence data) between life stages during both surveys. Additionally, the difference of the temperature experienced by the adult versus juveniles significantly increased between surveys for 8 of 25 species. We found evidence of a relationship between the difference of temperature experienced by juveniles and adults over time and one key functional trait (i.e. leaf area). Together, these results suggest that the temperatures experienced by adults versus juveniles became more decoupled over time for a subset of species, probably due to the combination of climate change and a recorded increase of canopy cover between the surveys resulting in higher rates of macroclimate than microclimate warming. 4. Synthesis. We document warming and canopy-cover induced changes in the difference of the temperature experienced by juveniles and adults. These findings have implications for forest management adaptation to climate change such as the promotion of tree regeneration by creating suitable species-specific microclimatic conditions. Such adaptive management will help to mitigate the macroclimate change in the understorey layer. [ABSTRACT FROM AUTHOR]

Studying functional traits and their relationships with tree growth has proved a powerful approach for understanding forest structure. These relationships are often expected to follow the classical resource economics perspective, where acquisitive leaves combined with acquisitive roots are expected to enhance resource uptake and tree growth. However, evidence for coordinated leaf and roots trait effects on growth is scarce and it remains poorly understood how these traits together determine tree growth. Here, we tested how leaf and root trait combinations explain tree growth.We collected data on leaf and root traits of 10 common tree species, and on soil carbon (C) and nitrogen (N) concentrations in a temperate forest in Michigan, US. Tree growth was calculated as the stem diameter increment between three censuses measured across 13,000 trees and modelled as a function of different combinations of leaf and root traits and soil properties.The two best models explaining tree growth included both specific leaf area (SLA), root diameter and soil C or N concentration, but their effects on growth were contingent on each other: thick roots were associated with high growth rates but only for trees with low SLA, and high SLA was related to fast growth but only for trees with thin roots. Soil C and N% negatively impacted the growth of trees with high SLA or high root diameter.Synthesis. In this study, resource economics did not explain the relationships between leaf and root traits and tree growth rates. First, for trees with low or intermediate SLA, thick roots may be considered as acquisitive, as they were associated with faster tree growth. Second, trees did not coordinate their leaf and root traits according to plant resource economics but enhanced their growth rates by combining thick (acquisitive) roots with conservative (low SLA) leaves or vice versa. Our study indicates the need to re‐evaluate the combined role of leaves and roots to unveil the interacting drivers of tree growth and, ultimately, of forest structure and suggests that different adaptive whole‐tree phenotypes coexist. [ABSTRACT FROM AUTHOR]

Communities are increasingly threatened by extreme weather events. The cumulative effects of such events are typically investigated by assessing community resilience, that is, the extent to which affected communities can achieve pre‐event states. However, a mechanistic understanding of the processes underlying resilience is frequently lacking and requires linking various measures of resilience to demographic responses within natural communities.Using 13 years of data from a shrub community that experienced a severe drought in 2005, we use generalized additive models to investigate temporal changes in three measures of resilience. We assess whether community‐weighted, species‐specific demographic traits such as longevity and reproductive output can predict changes in resilience and how the performance of these traits compares to more commonly used plant functional traits such as leaf area or root dry matter content.We find significant spatiotemporal variation in community dynamics after the drought. Overall, demographic traits are better at predicting absolute and relative resilience in total plant cover, but functional traits outperform demographic traits when resilience in community composition is assessed. All resilience measures show nonlinear and context‐specific responses to demographic and functional traits; and these responses depend strongly on the severity of initial drought impact.Synthesis. Our work demonstrates that a full picture of the mechanisms underlying community responses to drought requires the assessment of numerous species‐specific characteristics (including demographic and functional traits) and how these characteristics differentially affect complementary measures of community changes through time. [ABSTRACT FROM AUTHOR]

Plant species can show considerable morphological and functional variation along environmental gradients. This intraspecific trait variation (ITV) can have important consequences for community assembly, biotic interactions, ecosystem functions and responses to global change. However, directly measuring ITV across many species and wide geographic areas is often infeasible. Thus, a method to predict spatial variation in a species' functional traits could be valuable.We measured specific leaf area (SLA), height and leaf area (LA) of grasses across California, covering 59 species at 230 sampling locations. We asked how these traits change along climate gradients within each species and used machine learning to predict local trait values for any species at any location based on phylogenetic position, local climate and that species' mean traits. We then examined how much these local predictions alter patterns of assemblage‐level trait variation across the state.Most species exhibited higher SLA and grew taller at higher temperatures and produced larger leaves in drier conditions. The random forests predicted spatial variation in functional traits very accurately, with correlations up to 0.97. Because trait records were spatially biased towards warmer areas, and these areas tend to have higher SLA individuals within each species, species means of SLA were upwardly biased. As a result, using species means over‐estimates SLA in the cooler regions of the state. Our results also suggest that height may be substantially under‐predicted in the warmest areas.Synthesis. Using only species mean traits to characterize the functional composition of communities risks introducing substantial error into trait‐based estimates of ecosystem properties including decomposition rates or NPP. The high performance of random forests in predicting local trait values provides a way forward for estimating high‐resolution patterns of ITV without a massive data collection effort. [ABSTRACT FROM AUTHOR]

Climate extremes, such as abnormally dry and wet conditions, generate abrupt shifts in tree growth, a situation which is expected to increase under predicted climate conditions. Thus, it is crucial to understand factors determining short‐ and long‐term tree performance in response to higher frequency and intensity of climate extremes.We evaluated how three successive droughts and wet years influenced short‐ and long‐term growth of six dominant Iberian tree species. Within species variation in growth response to repeated dry and wet years was evaluated as a function of individual traits related to resource and water use (diameter at breast height [DBH], wood density [WD] and specific leaf area [SLA]) and tree‐to‐tree competition across climatically contrasted populations. Furthermore, we assessed how short‐term accumulated impacts of the repeated dry and wet years influenced long‐term growth performance.All species showed strong short‐term growth decreases and enhancements due to repeated dry and wet years. However, patterns of accumulated growth decreases (AcGD) and enhancements (AcGE) across climatically contrasting populations were species‐specific. Furthermore, individual trait data were weakly associated with either AcGD or AcGE and the few relevant associations were found for conifers. Intraspecific variations in tree growth responses to repeated climates extremes were large, and not explained by intraspecific variability in SLA and WD. Accumulated impacts of repeated dry and wet years were related to long‐term growth trends, showing how the recurrence of climate extremes can determine growth trajectories. The relationships of AcGD and AcGE with long‐term growth trends were more common in conifers species.Synthesis. Repeated climate extremes do not only cause short‐term growth reductions and enhancements but also determine long‐term tree growth trajectories. This result shows how repeated droughts can lead to growth decline. Conifers were more susceptible to the accumulated effects of extreme weather events indicating that in the future, more intense and frequent climate extremes will alter growth performance in forests dominated by these species. [ABSTRACT FROM AUTHOR]

Individual‐level demographic outcomes should be predictable upon the basis of traits. However, linking traits to tree performance has proven challenging likely due to a failure to consider physiological traits (i.e. hard‐traits) and the failure to integrate organ‐level and whole plant‐level trait information.Here, we modelled the survival rate and relative growth rate of trees while considering crown allocation, hard‐traits and local‐scale biotic interactions, and compared these models to more traditional trait‐based models of tree performance.We found that an integrative trait, total tree‐level photosynthetic mass (estimated by multiplying specific leaf area and crown area) results in superior models of tree survival and growth. These models had a lower AIC than those including the effect of initial tree size or any other combination of the traits considered. Survival rates were positively related to higher values of crown area and photosynthetic mass, while relative growth rates were negatively related to the photosynthetic mass. Relative growth rates were negatively related to a neighbourhood crowding index. Furthermore, none of the hard‐traits used in this study provided an improvement in tree performance models.Synthesis. Overall, our results highlight that models of tree performance can be greatly improved by including crown area information to generate a better understanding of plant responses to their environment. Additionally, the role of the hard‐traits in improving models of tree performance is likely dependent upon the level of stress (e.g. drought stress), micro‐environmental conditions or short‐term climatic variations that a particular forest experiences. [ABSTRACT FROM AUTHOR]

Environmental gradients act as potent filters on species distributions driving compositional shifts across communities. Compositional shifts may reflect differences in physiological tolerances to a limiting resource that result in broad distributions for tolerant species and restricted distributions for intolerant species (i.e. a nested pattern). Alternatively, trade‐offs in resource use or conflicting species' responses to multiple resources can result in complete turnover of species along gradients.We combined trait (leaf area, leaf mass per area, wood density and maximum height) and distribution data for 550 tree species to examine taxonomic and functional composition at 72 sites across strong gradients of soil phosphorus (P) and rainfall in central Panama.We determined whether functional and taxonomic composition was nested or turned over completely and whether community mean traits and species composition were more strongly driven by P or moisture.Turnover characterized the functional composition of tree communities. Leaf traits responded to both gradients, with species having larger and thinner leaves in drier and more fertile sites than in wetter and less fertile sites. These leaf trait–moisture relationships contradict predictions based on drought responses and suggest a greater role for differences in light availability than in moisture. Shifts in wood density and maximum height were weaker than for leaf traits with taller species dominating wet sites and low wood density species dominating P‐rich sites.Turnover characterized the taxonomic composition of tree communities. Geographic distances explained a larger fraction of variation for taxonomic composition than for functional composition, and community mean traits were more strongly driven by P than moisture.Synthesis. Our results offer weak support for the tolerance hypothesis for tree communities in central Panama. Instead, we observe functional and taxonomic turnover reflecting trade‐offs and conflicting species' responses to multiple abiotic factors including moisture, soil phosphorus and potentially other correlated variables (e.g. light). [ABSTRACT FROM AUTHOR]

Photosynthetic pathway is an important cause of growth rate variation between species such that the enhanced carbon uptake of C4 species leads to faster growth than their C3 counterparts. Leaf traits that promote rapid resource acquisition may further enhance the growth capacity of C4 species. However, how root economic traits interact with leaf traits, and the different growth strategies adopted by plants with C3 and C4 photosynthetic pathways is unclear. Plant economic traits could interact with, or act independently of, photosynthetic pathway in influencing growth rate, or C3 and C4 species could segregate out along a common growth rate–trait relationship.We measured leaf and root traits on 100+ grass species grown from seeds in a controlled, common environment to compare with relative growth rates (RGR) during the initial phase of rapid growth, controlling for phylogeny and allometric effects.Photosynthetic pathway acts independently to leaf and root functional traits in causing fast growth. Using C4 photosynthesis, plants can achieve faster growth than their C3 counterparts (by an average 0.04 g g−1 day−1) for a given suite of functional trait values, with lower investments of leaf and root nitrogen. Leaf and root traits had an additive effect on RGR, with plants achieving fast growth by possessing resource‐acquisitive leaf traits (high specific leaf area and low leaf dry matter content) or root traits (high specific root length and area, and low root diameter), but having both leads to an even faster growth rate (by up to 0.06 g g−1 day−1). C4 photosynthesis can provide a greater relative increase in RGR for plants with a 'slow' ecological strategy than in those with fast growth. However, above‐ground and below‐ground strategies are not coordinated so that species can have any combination of 'slow' or 'fast' leaf and root traits.Synthesis. C4 photosynthesis increases growth rate for a given combination of economic traits, and significantly alters plant nitrogen economy in the leaves and roots. However, leaf and root economic traits act independently to further enhance growth. The fast growth of C4 grasses promotes a competitive advantage under hot, sunny conditions. [ABSTRACT FROM AUTHOR]

Trait values affect how plants function, with consequences that propagate through scales of ecological organization to affect ecosystem function. However, the pathway connecting trait expression to ecosystem function is complicated by feedbacks: trait expression may vary within species in response to community diversity, and trait expression also determines a community's functional diversity. The predictability and consequences of interactions between trait expression and community diversity are poorly understood, particularly in forest ecosystems.Here we quantify the extent to which light access—which past studies suggest affects trait expression and differs as a result of interactions among plants—differs consistently with community diversity and explains intraspecific trait variation in trees. In a common garden, trees of five angiosperm and seven gymnosperm species were planted to form 37 communities ranging widely in species and functional diversity whereby confounding environmental variation was minimized. We sampled leaves of each species to characterize intraspecific variation within and among communities in three traits—leaf size, specific leaf area and nitrogen concentration—and estimated each leaf's access to light.We found that light access explained a substantial portion of trait variation within all species, species tended to receive less light in more diverse communities and effects of community diversity on trait expression tended to be mediated by light.Synthesis. This study shows that community diversity affects leaf trait plasticity in young trees through its effects on light availability. Moreover, trait responses across angiosperms and gymnosperms were remarkably similar, showing that shared biophysical constraints overwhelm divergent evolutionary histories. Together, these results illustrate how leaf trait expression responds to, and may subsequently shape, diversity in young tree communities in largely predictable ways via resource‐based interactions, with consequences that may scale from individuals to ecosystems. [ABSTRACT FROM AUTHOR]

Plants are enormously diverse in their traits and ecological adaptation, even within given ecosystems, such as tropical rainforests. Accounting for this diversity in vegetation models poses serious challenges. Global plant functional trait databases have highlighted general trait correlations across species that have considerably advanced this research program. However, it remains unclear whether trait correlations found globally hold within communities, and whether they extend to drought tolerance traits.For 134 individual plants spanning a range of sizes and life forms (tree, liana, understorey species) within an Amazonian forest, we measured leaf drought tolerance (leaf water potential at turgor loss point, πtlp), together with 17 leaf traits related to various functions, including leaf economics traits and nutrient composition (leaf mass per area, LMA; and concentrations of C, N, P, K, Ca and Mg per leaf mass and area), leaf area, water‐use efficiency (carbon isotope ratio), and time‐integrated stomatal conductance and carbon assimilation rate per leaf mass and area. We tested trait coordination and the ability to estimate πtlp from the other traits through model selection. Performance and transferability of the best predictive model were assessed through cross‐validation.Here πtlp was positively correlated with leaf area, and with N, P and K concentrations per leaf mass, but not with LMA or any other studied trait. Five axes were needed to account for >80% of trait variation, but only three of them explained more variance than expected at random. The best model explained only 30% of the variation in πtlp, and out‐sample predictive performance was variable across life forms or canopy strata, suggesting a limited transferability of the model.Synthesis. We found a weak correlation among leaf drought tolerance and other leaf traits within a forest community. We conclude that higher trait dimensionality than assumed under the leaf economics spectrum may operate among leaves within plant communities, with important implications for species coexistence and responses to changing environmental conditions, and also for the representation of community diversity in vegetation models. [ABSTRACT FROM AUTHOR]

Plants protect themselves against herbivore attacks with physical traits and toxic secondary metabolites. Levels of plant defences and herbivore performance might shift under climate warming, particularly in alpine habitats, where herbivore pressure is currently low. Plant responses to warming should be driven by species‐specific shifts in physical and chemical defence traits.We investigated the association between plant leaf physical and chemical traits and herbivory under current and warmer climates in three grasslands along a subalpine to alpine gradient. Specifically, we measured the rate of in situ natural herbivory, and performed bioassays to measure overall plant species‐level resistance using the extreme generalist non‐native caterpillar Spodoptera littoralis. We simulated warmer conditions by using open‐top chambers and assessed the effect of warming on leaf physical and chemical traits, and how trait changes affect caterpillar performance.Natural herbivory and caterpillar performance were associated with plant physical traits, including specific leaf area, and with ordination axes representing dimensions of the plant chemical profile. We found that the warming treatment independently decreased the number of distinct chemical compounds per species, and marginally increased specific leaf area. Changes in leaf functional traits were not systematically associated with changes in caterpillar performance.Synthesis. Plant physical traits and chemical profiles are both related to natural herbivory and plant resistance against Spodoptera littoralis. While leaf physical and chemical traits of high elevation plants were modified by the warming treatment, these changes did not result in predictable effects on plant resistance against herbivores. [ABSTRACT FROM AUTHOR]

Plant species composition and diversity are known to change across local gradients of light, moisture and nutrients, but ecologists still have a relatively limited understanding of how communities respond to multiple limiting resources.We used a trait‐based approach to investigate how the functional composition and diversity of forest understorey plant communities change along gradients in light, soil moisture and nitrogen availability. We used a total of seven leaf, root and whole‐plant traits for 55–78 species, and estimated the effects of the three resources on the mean and dispersion of these traits in understorey plant communities across 50 forest sites.Soil moisture and nitrogen availability (C/N ratio) both influenced plant community traits, but light availability (canopy openness) did not. Generally, increases in moisture and nitrogen both resulted in shifts towards more acquisitive resource use strategies, including greater leaf area, specific leaf area and maximum plant height, and lower leaf dry matter content, root dry matter content and rooting depth. Functional diversity of most traits also increased with increasing soil moisture and nitrogen. Although most traits varied with soil moisture on nitrogen‐poor sites, moisture did not influence of the distribution of any traits on nitrogen‐rich sites.Synthesis. Independent co‐limitation of soil moisture and nitrogen appeared to influence the functional composition and diversity of understorey vegetation in our study area. The co‐occurrence of species with resource acquisitive and conservative strategies on nitrogen‐rich sites may make plant communities relatively resistant to changes to soil moisture. These results suggest that altered precipitation regimes under climate change could lead to greater changes in the composition and diversity of plant communities on nutrient‐poor soils than on nutrient‐rich soils. [ABSTRACT FROM AUTHOR]

Both intra‐ and interspecific differences in traits may modulate interactions between plants. Two mechanisms are hypothesized to regulate these effects: competitive hierarchies and trait dissimilarities, but it is unclear how the prevalence of each might depend on environmental conditions and on intra and interspecific differences.We sowed six replicates of all possible pairwise combinations across eight annual species (including conspecific competition and individuals without competitors), in pots under two levels of fertilization. We measured above‐ and below‐ground traits and total biomass of the focal individuals. We expressed competition as the decrease in biomass of focal individuals relative to biomass without competition, and modelled competition using directional (hierarchy) or non‐directional (dissimilarity) trait differences, with or without intraspecific variability (ITV).We found evidence of different trait hierarchies operating under different fertilization conditions but little support for trait dissimilarities. The negative effect of competition on focal plants increased with the height of the competitors in both of fertilization levels. Further, in unfertilized conditions, plants with lower specific leaf area (SLA) and larger root systems experienced less competition. Including ITV in trait hierarchies substantially improved our ability to predict the intensity of competition. This was partly due to ITV reducing competitive hierarchies.Synthesis. Our results underscore the importance of traits in driving interactions among plants. Competitive relationships between species depend on complex interactions between trait intra and interspecific differences and resource availability. ITV appears to be a mechanism capable of reducing trait hierarchies, and hence the intensity of competition between coexisting plants. [ABSTRACT FROM AUTHOR]

Dominant species can act as a biotic filter in structuring plant communities by constraining the establishment and survival of subordinate species. The effect of intraspecific trait variability of dominant species on the functional response of subordinate species, however, is not well understood.We quantified intraspecific variation in four functional traits of 26 subordinate species in an experimental grassland established with two population sources (i.e. cultivars and local ecotypes) of three dominant grasses (Sorghastrum nutans, Andropogon gerardii and Schizachyrium scoparium) and three pools of subordinate species (each from one origin) within each of the dominant grass source treatments.Twenty of the 26 subordinate species exhibited intraspecific trait variability for one trait or more in response to dominant species population source, and variation among population sources of the dominant species was non‐random. Dominant grass population source affected intraspecific variability in functional traits of multiple subordinate species. Cultivar sources of the dominant grasses and some of the subordinate species that established with them had higher and generally more variable functional leaf area and leaf nitrogen content compared to local ecotypes of the dominant grasses and the subordinate species that established with them. Local ecotype sources of the dominant grasses increased leaf area based functional diversity of subordinate species.Synthesis. This study provides evidence that intraspecific trait variability in dominant species acts as a biotic filter to constrain niche availability and dimensionality affecting trait variation of subordinate species during community assembly. [ABSTRACT FROM AUTHOR]

Exploring the mechanisms underlying the change in ecosystem productivity under anthropogenic nitrogen (N) inputs is of fundamental ecological interest. It has been proposed that functional traits, environmental factors and species richness are central drivers linking ecosystem productivity with environmental change. However, few studies have considered the joint effects of functional traits, environmental factors and species richness on ecosystem productivity under increasing N inputs.We established a N‐manipulation experiment in a Tibetan alpine steppe in 2013. Using structural equation models, we assessed the effects of N‐induced changes in environmental factors, species richness and trait metrics (mean, variance, skewness and kurtosis of trait distribution) on gross ecosystem productivity as well as three resource use efficiencies (water, light and phosphorus (P) use efficiencies), based on measurements during the peak growing season in 2016.We found that both light and P use efficiencies decreased under N enrichment, largely due to the N‐induced decline in functional diversity of leaf P concentration. However, both gross ecosystem productivity and water use efficiency exhibited initial increases and subsequent slight decreases with N addition. These nonlinear patterns were closely associated with both the increased morphological trait (i.e. mean of leaf area) and decreased diversity of leaf P concentration.Synthesis. Our results illustrate how N‐induced changes in functional traits may have dual effects on ecosystem productivity: the stimulating effects of the dominant trait identity via increasing canopy light interception versus the inhibiting effect of decreasing trait diversity via declining resource use efficiencies. Our results highlight the importance of including functional traits in land surface models to improve predictions of the response of ecosystem function to N inputs. Our results illustrate how N‐induced changes in functional traits may have dual effects on ecosystem productivity: the stimulating effects of the dominant trait identity via increasing canopy light interception versus the inhibiting effect of decreasing trait diversity via declining resource use efficiencies. Our results highlight the importance of including functional traits in land surface models to improve predictions of the response of ecosystem function to N inputs.. [ABSTRACT FROM AUTHOR]

Tropical plant assemblages can be taxonomically and phylogenetically impoverished by chronic anthropogenic disturbance (CAD), such as firewood collection and extensive grazing. However, to what extent the functional dimension responds to CAD is still unclear. Such knowledge is urgently required for predicting, preventing or even reversing the impacts of CAD.Chronic anthropogenic disturbance may operate as an ecological filter by selecting functional trait values (e.g. low wood density), thereby altering the functional composition and diversity of plant assemblages. We tested this hypothesis using 29 woody plant assemblages across three ontogenetic stages (seedlings, saplings and adults) in a 220‐km2 landscape of the Caatinga, northeast Brazil. We adopted a CAD index consisting of four indicators (proximity to urban centre and houses and the density of both people and livestock) and tested how well it explained the functional diversity and effect sizes (richness, evenness and dispersion) and composition (community‐weighted mean).Chronic anthropogenic disturbance affected several functional metrics across the three ontogenetic stages. However, CAD effects were stronger in adult communities by negatively affecting functional richness, dispersion and their effect sizes. CAD also altered the functional composition of leaf mass per area, woody density and leaf area of adult assemblages. Sapling communities were affected in terms of functional composition (leaf area, leaf dry matter and wood density), with positive and negative effects, while seedling assemblages responded positively to CAD only in terms of functional evenness and its effect size. Some changes in functional metrics were influenced by dominant Euphorbiaceae species across ontogenetic stages, especially in terms of leaf area and woody density.Synthesis. Chronic anthropogenic disturbance is an important driver of plant‐community functional organization across ontogenetic stages in the Caatinga. Adult assemblages are particularly sensitive and tend to lose functional niche space and support more acquisitive rather than conservative strategies as chronic anthropogenic disturbance increases. The proliferation of Euphorbiaceae disturbance‐adapted species can explain part of the community responses to chronic anthropogenic disturbance. Our findings highlight the ecological effects of chronic anthropogenic disturbance and show that it is a key influence on tropical biotas. Changes in plant functional traits associated with plant resource use are likely to affect ecosystem functioning and services provided by Caatinga. [ABSTRACT FROM AUTHOR]

Ecosystem processes are driven by both environmental variables and the attributes of component species. The extent to which these effects are independent and/or dependent upon each other has remained unclear. We assess the extent to which climate affects net primary productivity (NPP) both directly and indirectly via its effect on plant size and leaf functional traits.Using species occurrences and functional trait databases for North and South America, we describe the upper limit of woody plant height within 200 × 200 km grid‐cells. In addition to maximum tree height, we quantify grid‐cell means of three leaf traits (specific leaf area, and leaf nitrogen and phosphorus concentration) also hypothesized to influence productivity. Using structural equation modelling, we test the direct and indirect effects of environment and plant traits on remotely sensed MODIS‐derived estimates of NPP, using plant size (satellite‐measured canopy height and potential maximum tree height), leaf traits, growing season length, soil nutrients, climate and disturbances as explanatory variables.Our results show that climate affects NPP directly as well as indirectly via plant size in both tropical and temperate forests. In tropical forests NPP further increases with leaf phosphorus concentration, whereas in temperate forests it increases with leaf nitrogen concentration. In boreal forests, NPP most strongly increases with increasing temperature and neither plant size nor leaf traits have a significant influence.Synthesis. Our results suggest that at large spatial scales plant size and leaf nutrient traits can improve predictions of forest productivity over those based on climate alone. However, at higher latitudes their role is overridden by stressful climate. Our results provide independent empirical evidence for where and how global vegetation models predicting carbon fluxes could benefit from including effects of plant size and leaf stoichiometry. [ABSTRACT FROM AUTHOR]

The use of plant traits to predict ecosystem functions has been gaining growing attention. Above‐ground plant traits, such as leaf nitrogen (N) content and specific leaf area (SLA), have been shown to strongly relate to ecosystem productivity, respiration and nutrient cycling. Furthermore, increasing plant functional trait diversity has been suggested as a possible mechanism to increase ecosystem carbon (C) storage. However, it is uncertain whether below‐ground plant traits can be predicted by above‐ground traits, and if both above‐ and below‐ground traits can be used to predict soil properties and ecosystem‐level functions.Here, we used two adjacent field experiments in temperate grassland to investigate if above‐ and below‐ground plant traits are related, and whether relationships between plant traits, soil properties and ecosystem C fluxes (i.e. ecosystem respiration and net ecosystem exchange) measured in potted monocultures could be detected in mixed field communities.We found that certain shoot traits (e.g. shoot N and C, and leaf dry matter content) were related to root traits (e.g. root N, root C:N and root dry matter content) in monocultures, but such relationships were either weak or not detected in mixed communities. Some relationships between plant traits (i.e. shoot N, root N and/or shoot C:N) and soil properties (i.e. inorganic N availability and microbial community structure) were similar in monocultures and mixed communities, but they were more strongly linked to shoot traits in monocultures and root traits in mixed communities. Structural equation modelling showed that above‐ and below‐ground traits and soil properties improved predictions of ecosystem C fluxes in monocultures, but not in mixed communities on the basis of community‐weighted mean traits.Synthesis. Our results from a single grassland habitat detected relationships in monocultures between above‐ and below‐ground plant traits, and between plant traits, soil properties and ecosystem C fluxes. However, these relationships were generally weaker or different in mixed communities. Our results demonstrate that while plant traits can be used to predict certain soil properties and ecosystem functions in monocultures, they are less effective for predicting how changes in plant species composition influence ecosystem functions in mixed communities. [ABSTRACT FROM AUTHOR]

The fitness of individual species depends on their ability to persist and establish at low densities, just as the diversity of ecological communities depends on the establishment and persistence of low‐density, "invader" species. Theory predicts that abiotic conditions and the competitive make‐up of resident communities jointly shape invader fitness, limiting the phenotypic identity of successful invaders.We use an invasion experiment to ask how competitive traits of 20 introduced plant species alter their absolute fitness in fragments that differ in size, abiotic conditions, and traits of the resident community.We show that abiotic conditions interact with both invader traits and resident functional diversity to determine invader survival. Optimal invader traits depended on the soil characteristics, while greater resident trait diversity lowered invader fitness and had especially strong effects in low‐resource environments. Unlike other abiotic conditions, fragment size had consistent effects irrespective of invader identity, decreasing survival in larger fragments.Synthesis. Our results illustrate how the abiotic environment mediates the effects of resident and invader traits on establishment, creating fitness landscapes that structure local diversity and the functional identities of successful species. Our results illustrate how the abiotic environment mediates the effects of resident and invader traits on establishment, creating fitness landscapes that structure local diversity and the functional identities of successful species. [ABSTRACT FROM AUTHOR]

Litter decomposition plays important roles in carbon and nutrient cycling. In dryland, both microbial decomposition and abiotic degradation (by UV light or other forces) drive variation in decomposition rates, but whether and how litter traits and position determine the balance between these processes is poorly understood., We investigated relationships between litter quality and their decomposition rates among diverse plant species in a desert ecosystem in vertically contrasting positions representing distinct decomposition environments driven by different relative contributions of abiotic and microbial degradation. Thereto, leaf litter samples from 17 desert species were sealed into litterbags and placed on the soil surface under strong solar exposure vs. shade conditions, or buried in the soil at 10 cm depth, for a whole year., Litter decomposition rates were 21% and 17% higher in burial and light-exposed treatments, respectively, than those in shade. Leaf traits, i.e. specific leaf area ( SLA), litter C:N ratio and lignin concentration could predict litter decomposition to some degree, but their predictive power was dependent on litter position. However, multiple linear regressions showed that SLA, litter C and P significantly affected k values for leaf litter decomposition besides litter position, with SLA standing out as a strong determinant of litter decomposition rate as related either to solar radiation or the environment below the soil surface. Furthermore, the interspecific differences in litter decomposition rates decreased over time, implying that afterlife effects of leaf traits on decomposition were attenuated., Synthesis. These findings suggest that abiotic photodegradation and soil burial mediated microbial decomposition could be responsible for higher than expected litter turnover in dryland. They point to a dual role of specific leaf area ( SLA) as a promotor of decomposition rates: via relative exposure of the leaf surface to abiotic factors such as UV light vs. to soil moisture and microbes under soil burial. [ABSTRACT FROM AUTHOR]

Establishing trade-offs among traits and the degree to which they covary along environmental gradients has become a key focal point in the effort to develop community ecology into a predictive science. While there is evidence for these relationships across global data sets, they are often too broad in scale and do not consider the particularities of local to regional species pools. This decreases their usefulness for developing predictive models at scales relevant for conservation and management., We tested for trade-offs between traits and relationships with environmental gradients in trees and shrubs sampled across southern African savannas and explored evidence for acquisitive versus conservative resource-use strategies using a phylogenetically explicit approach., We found a distinct trade-off between two major poles of specialization indicative of acquisitive (high leaf nitrogen concentration, leaf phosphorus concentration, leaf N:P, specific leaf area and average leaf area) and conservative resource-use strategies (high leaf carbon to nitrogen ratios (C:N), tensile strength and leaf dry matter content). Although we found that trait variance and species occurrence were constrained by phylogeny, phylogenetically informed analyses did not contradict non-phylogenetic analyses, strengthening relationships in most cases., The high intrasite trait variability and weak relationships with soils and climate may in part be explained by the high levels of deciduousness and disturbance (i.e. fire and herbivory) inherent in African savannas., Synthesis. The relationships between traits and between traits and environmental gradients were far weaker than, and often contradictory to, broad-scale studies that compare these relationships across biomes and growth forms, cautioning against making generalizations about relationships at specific sites based on broad-scale analyses. [ABSTRACT FROM AUTHOR]

For plants competing for light, grasslands represent complex environments. Grassland microhabitats vary in the amount of available light and in the spatial distribution of patches with full sunlight, light shade and deep shade. Plant populations have been shown to adapt to specific competitors and shading conditions, but it is an open question how tightly the responses of populations to different shading situations are linked to the light availability previously experienced in the field., Using maternal families collected in grasslands ranging from open to closed canopies, I tested the effects of no shading, homogeneous and heterogeneous shade created in the glasshouse on trait expression in the annual Erodium cicutarium. Heterogeneous shading was simulated by a patchwork of single and double layers of light filters lowering the R:FR ratio of transmitted light and clear filters simulating gaps., Heterogeneous shading induced a stronger shade avoidance response than homogeneous shading, with larger leaf length, greater vegetative height and larger specific leaf area. Time to first flowering was longer under heterogeneous shading, and plants produced less fruits., Populations differed in their time to first flowering under the shading treatments, and these differences could be traced back to light availability measured in the field. Plants from populations with lower light availability showed a postponed date of first flowering even if they were not shaded. These differences were attributable to plasticity of the maternal families. Across shading treatments, plants from low-light environments produced more above-ground biomass., Synthesis. This study indicates that there is a close linkage between the light availability experienced in the field and the ability of following generations to respond to shading. Low average light availability experienced in the past seems to induce a trade-off of vegetative growth against early flowering, providing the following generations with the capacity to overtop neighbours. This capacity is utilized especially if plants experience a mixture of gaps and deep shade. [ABSTRACT FROM AUTHOR]

Understanding how intraspecific trait variability ( ITV) responds to both abiotic and biotic constraints is crucial to predict how individuals are assembled in plant communities, and how they will be impacted by ongoing global environmental change., Three key functional traits [plant height, leaf area ( LA) and specific leaf area ( SLA)] were assessed to quantify the range of ITV of four dominant plant species along a rainfall gradient in semi-arid Mediterranean shrublands. Variance partitioning and confirmatory multilevel path analyses were used to assess the direct and indirect effects of rainfall, space limitation (crowding) and neighbouring plant traits on ITV., The direct effect of the local neighbourhood on the trait values of subordinate individuals was as strong as the effect of rainfall. The indirect effect of rainfall, however, mediated by the effect of the local neighbourhood on the trait values of subordinate individuals, was weak. Rainfall decreased the height and SLA of subordinate individuals, but increased their LA. Neighbouring plant traits were just as strong predictors as crowding in explaining changes in ITV., Synthesis. Our study provides a framework to disentangle the direct effects of abiotic factors and their indirect effects on ITV mediated by the local neighbourhood. Our results highlight that abiotic and biotic constraints are both substantial sources of trait variations at the individual level, and can blur processes underlying changes in ITV. Considering and disentangling combined sources with an individual perspective would help to refine our predictions for community assembly and functional ecology. [ABSTRACT FROM AUTHOR]

Despite a long history of research, we lack a comprehensive understanding of the reasons behind pronounced variation in foliar losses to insects among plant species. Our aim was to test the hypothesis that plant functional traits and/or ecological strategies are good predictors of the background losses of woody plant foliage to insects (i.e. losses occurring when herbivore populations are at their 'normal' densities) at the global scale., We conducted a quantitative synthesis of published and original data on foliar losses of 793 species of woody plants belonging to 128 families from ca. 500 localities world-wide, representing tropical, temperate and polar climate zones., The background foliar losses to insects varied among plant life forms, increasing from dwarf shrubs to large trees, and were higher in inherently fast-growing species than in slow-growing species. These patterns supported predictions of both the apparency and growth rate (resource availability) hypotheses for data combined across localities, but only outside the tropics., Foliar losses to insects slightly but significantly increased with specific leaf area ( SLA) in all climate zones., No differences were noted in background herbivory between woody plant species with deciduous and evergreen foliage, with different shade tolerance and with different successional status., Synthesis. Factors affecting the distribution of herbivory among species of woody plants differed among the climate zones, and the predictive power of at least some of the theories/hypotheses addressing plant-herbivore interactions at large spatial scales varies among climates and/or biomes. The average background losses of woody plant foliage to insects across localities can be predicted from the inherent growth rate of the plant species, its life form and SLA, although these plant characteristics jointly explain only a minor part of the total variation observed in the primary data. [ABSTRACT FROM AUTHOR]