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Identifying patterns and drivers of plant community assembly has long been a central issue in ecology. Many studies have explored the above questions using a trait‐based approach; however, there are still unknowns around how patterns of plant functional traits vary with environmental gradients. In this study, the responses of individual and multivariate trait dispersions of 134 species to soil resource availability were examined based on correlational analysis and torus‐translation tests across four spatial scales in a subtropical forest, China. Results indicated that different degrees of soil resource availability had different effects on trait dispersions. Specifically, limited resource (available phosphorus) showed negative relationships with trait dispersions, non‐limited resource (available potassium) showed positive relationships with trait dispersions, and saturated resource (available nitrogen) had no effect on trait dispersions. Moreover, compared with the stem (wood density) and architectural trait (maximum height), we found that leaf functional traits can well reflect the response of plants to nutrient gradients. Lastly, the spatial scale only affected the magnitude but not the direction of the correlations between trait dispersions and environmental gradients. Overall, the results highlight the importance of soil resource availability and spatial scale in understanding how plant functional traits respond to environmental gradients. [ABSTRACT FROM AUTHOR]

Aim: Ecological specialization is defined by the variety of environments species occupy. Identifying the mechanisms that influence specialization is critical to understand patterns of species coexistence and biodiversity. However, the functional attributes that result in specialization are still unknown. Similarly, there is contrasting evidence between the degree of specialization and the local abundance of species. We investigated whether specialist and generalist plant species (a) are associated with distinct functional profiles, using core plant functional traits and strategies, (b) show similar functional variation and (c) perform at the local scale. Location: France. Taxon: Herbaceous plants. Methods: We analysed the structure of a bipartite network that includes the occurrences of ~2,900 plant species at ~90,000 sites to identify ecologically consistent sets of species and sites (i.e. 'modules'). This innovative approach then enabled us to define a metric of specialization, by quantifying occurrences of species at sites that belong to one or several modules. We used functional traits related to resource acquisition, competition for light and dispersal ability, as well as indices of competitive, stress tolerance and ruderal strategies. Results: We identified five major modules in the bipartite network related to different environments and composed of species with differing functional attributes. Specialist species were less competitive and shorter, and had higher stress tolerance and stronger resource conservation, while generalist species were taller. Generalists were also more similar to each other than specialists. In addition, specialists had higher local abundances and occurred in communities with plants of similar height. Main conclusions: We found distinctive functional signatures of specialist and generalist species in grassland communities across diverse environments at regional and community scales. By testing classic macro‐ecological hypotheses, network metrics can benefit community ecology by identifying distinct ecological units at a large scale and quantifying the links developed by species. [ABSTRACT FROM AUTHOR]

Aims: Uncovering the importance of soil and plant characteristics in driving the legacy effects of nitrogen (N) deposition on plant community nutrient stoichiometry would improve our understanding of plant-soil interaction during restoration of historically N-enriched ecosystems. Methods: Based on a field experiment with the cessation of six-year N addition in a temperate steppe of northern China, we measured concentrations and stoichiometry of N and phosphorus (P) in soils and different plant functional groups, under both mown and unmown conditions. Results: Historical N addition did not affect soil total and available N and P concentrations and stoichiometry, but significantly altered plant community composition. Plant nutrient concentrations and N:P ratios significantly differed among four plant functional groups. The concentrations and stoichiometric ratios of N and P between soils and plants were generally not correlated. The positive legacy effects of N addition on community N:P stoichiometry were caused by the biomass enhancement of tall bunchgrass, the functional group with the highest N:P ratios. Conclusions: Changes in plant community composition instead of soil nutrient status were the main driver for the positive legacy effects of N enrichment on plant community stoichiometry. Given that the recovery of community composition after the cessation of N deposition is generally slow, our findings indicate that the legacy effects of N deposition on soil nutrient cycling would persist in long-term due to the importance of plant-mediated pathway. [ABSTRACT FROM AUTHOR]

Plant germination ecology involves continuous interactions between changing environmental conditions and the sensitivity of seed populations to respond to those conditions at a given time. Ecologically meaningful parameters characterizing germination capacity (or dormancy) are needed to advance our understanding of the evolution of germination strategies within plant communities. The germination traits commonly examined (e.g., maximum germination percentage under optimal conditions) may not adequately reflect the critical ecological differences in germination behavior across species, communities, and seasons. In particular, most seeds exhibit primary dormancy at dispersal that is alleviated by exposure to dry after‐ripening or to hydrated chilling to enable germination in a subsequent favorable season. Population‐based threshold (PBT) models of seed germination enable quantification of patterns of germination timing using parameters based on mechanistic assumptions about the underlying germination physiology. We applied the hydrothermal time (HTT) model, a type of PBT model that integrates environmental temperature and water availability, to study germination physiology in a guild of coexisting desert annual species whose seeds were after‐ripened by dry storage under different conditions. We show that HTT assumptions are valid for describing germination physiology in these species, including loss of dormancy during after‐ripening. Key HTT parameters, the hydrothermal time constant (θHT) and base water potential distribution among seeds (Ψb(g)), were effective in describing changes in dormancy states and in clustering species exhibiting similar germination syndromes. θHT is an inherent species‐specific trait relating to timing of germination that correlates well with long‐term field germination fraction, while Ψb(g) shifts with depth of dormancy in response to after‐ripening and seasonal environmental variation. Predictions based on variation among coexisting species in θHT and Ψb(g) in laboratory germination tests matched well with 25‐yr observations of germination dates and fractions for the same species in natural field conditions. Seed dormancy and germination strategies, which are significant contributors to long‐term species demographics under natural conditions, can be represented by readily measurable functional traits underlying variation in germination phenologies. [ABSTRACT FROM AUTHOR]

Functional trait databases are powerful tools in ecology, though most of them contain large amounts of missing values. The goal of this study was to test the effect of imputation methods on the evaluation of trait values at species level and on the subsequent calculation of functional diversity indices at community level using functional trait databases. Two simple imputation methods (average and median), two methods based on ecological hypotheses, and one multiple imputation method were tested using a large plant trait database, together with the influence of the percentage of missing data and differences between functional traits. At community level, the complete-case approach and three functional diversity indices calculated from grassland plant communities were included. At the species level, one of the methods based on ecological hypothesis was for all traits more accurate than imputation with average or median values, but the multiple imputation method was superior for most of the traits. The method based on functional proximity between species was the best method for traits with an unbalanced distribution, while the method based on the existence of relationships between traits was the best for traits with a balanced distribution. The ranking of the grassland communities for their functional diversity indices was not robust with the complete-case approach, even for low percentages of missing data. With the imputation methods based on ecological hypotheses, functional diversity indices could be computed with a maximum of 30% of missing data, without affecting the ranking between grassland communities. The multiple imputation method performed well, but not better than single imputation based on ecological hypothesis and adapted to the distribution of the trait values for the functional identity and range of the communities. Ecological studies using functional trait databases have to deal with missing data using imputation methods corresponding to their specific needs and making the most out of the information available in the databases. Within this framework, this study indicates the possibilities and limits of single imputation methods based on ecological hypothesis and concludes that they could be useful when studying the ranking of communities for their functional diversity indices. [ABSTRACT FROM AUTHOR]

The traditional way of interpreting environmental and management effects on floristic composition based on phyto-sociological classification is increasingly accompanied by a trait-based approach. Plant functional traits (PFT) enable us to link morphological, physiological and phenological plant properties to their functions. Recent research on PFT has significantly improved our understanding on competitive ability of species, resulting species abundance and ecosystem functioning, through investigations of ecological strategies, community assembly theory and functional diversity. In this paper, we review the wide applicability of the trait approach in grassland science. The paper summarizes the power of PFT, the variation along soil nutrient gradients, and gives a case-by-case conceptual generalization of mechanisms of interacting traits at plant and canopy scale. We highlight the main trade-offs among traits and trait syndromes that are prospects for plant response to nutrient gradient and consequently for ecosystem processes. We also discuss the role of intraspecific variability in PFT for multiple ecological issues. Links between functional ecology and grassland science are also identified in order to establish research opportunities. For managed grasslands, we believe that progress in these links will allow us to address broad and timely questions regarding community dynamics driven by resource availability and the consequent multifunctionality of these grasslands. [ABSTRACT FROM AUTHOR]

Only a few studies have examined responses of grassland functional diversity to management and major environmental gradients, in order to address the question of whether grassland use can promote functional divergence. For five grassland sites in Israel, Portugal, the Czech Republic, Mediterranean France, and the French Alps, where traditional grassland management is being abandoned, we quantified community-weighted means (CWM) and functional divergence (FDvg) for the three Leaf-Height-Seed (LHS) traits, individually and in combination. Responses of CWM and FDvg to land use were analyzed by mixed linear models with aridity, phosphorus, fertility, and the fractions of grasses and annuals as covariates.Responses of community-weighted traits to land use were consistent with current knowledge. More intense management favored plants with more rapid resource acquisition (high Specific Leaf Area, or SLA), whereas abandonment or less intense grassland management increased the dominance by tall plants with more conservative strategies (low SLA). Seed weight did not respond to land use. For the three traits and their combination, functional divergence decreased in response to land use change overall. Detailed responses, however, varied depending on sites and especially their climate. At the two French sites, traditional site management promoted functional divergence within communities by suppressing dominance by large perennial tussocks, whereas at the two Mediterranean sites it is likely that the drier climate promoted a functionally diverse pool of species tolerant to grazing.This study demonstrates how simultaneous analyses of variations in community-mean traits and functional divergence for a focused set of traits offer promising avenues to understand mechanisms of community response to environmental change. [ABSTRACT FROM AUTHOR]

Background and Aims Predicting the response of plant communities to variation in resources and disturbance is still a challenge, because findings depend on how ecological gradients are characterized and how grassland functional composition is assessed. Focusing on leaf dry matter content (LDMC), the efficacy of different methods for evaluating the best response of plant communities to either environmental or disturbance change is examined. Methods Data were collected on 69 grasslands located at four sites in the Pyrenees and Massif Central. N-Ellenberg indices and plant nutrient content (Ni) were compared to assess fertility, and either LDMC (meas) measured or calculated from a trait database for which traits were measured under the same environmental conditions (db). Management regime (MR) was characterized in terms of categories (grazing, cutting) and plant height. Key Results LDMCdb was positively correlated to LDMCmeas, but depended significantly on site temperature. N-Ellenberg and Ni were significantly correlated, and there was a significant effect of MR and temperature. LDMC responded to fertility, MR and temperature. Replacing MR by plant height in an REML analysis reduced the uncertainty of the LDMC prediction. LDMC was correlated to plant height at community level, whereas the correlation was weak at species level. Differences in LDMC between plant communities under any of the management regimes were significantly correlated to the standing herbage mass. Conclusion The N-Ellenberg index is a better indicator of fertility than Ni which is short-term and environment-dependent. LDMC taken from a database allows plant trait variation due to species abundance (excluding variation due to trait plasticity in response to management) to be captured. So the former is better suited for assessing agricultural services that mainly depend on plant phenology and tissue composition. LDMC responded to defoliation regime in addition to fertility because plant height is roughly correlated with LDMC at plant community level. [ABSTRACT FROM PUBLISHER]

1. Trait-based approaches applied to community ecology have led to a considerable advance in understanding the effect of environmental filters on species assembly. Although plant traits are known to vary both between and within species, little is known about the role of intraspecific trait variability in the non-random assembly mechanisms controlling the coexistence of species, including habitat filtering and niche differentiation. 2. We investigate the role of intraspecific variability in three key functional traits – specific leaf area (SLA), leaf dry matter content (LDMC) and height – in structuring grassland communities distributed along a flooding gradient. We quantified the contribution of intraspecific variability relative to interspecific differences in the trait–gradient relationship, and we used a null model approach to detect patterns of habitat filtering and niche differentiation, with and without intraspecific variability. 3. Community mean SLA and height varied significantly along the flooding gradient and intraspecific variability accounted for 44% and 32%, respectively, of these trait–gradient relationships. LDMC did not vary along the gradient, with and without accounting for intraspecific variability. Our null model approach revealed significant patterns of habitat filtering and niche differentiation for SLA and height, but not for LDMC. More strikingly, considering intraspecific trait variability greatly increased the detection of habitat filtering and was necessary to detect niche differentiation processes. 4. Synthesis. Our study provides evidence for a strong role of intraspecific trait variability in community assembly. Our findings suggest that intraspecific trait variability promotes species coexistence, by enabling species to pass through both abiotic and biotic filters. We argue that community ecology would benefit from more attention to intraspecific variability. [ABSTRACT FROM AUTHOR]

Understanding disturbance effects on species diversity and functional diversity is fundamental to conservation planning but remains elusive. We quantified species richness, diversity, and evenness and functional richness, diversity, and evenness of riparian and upland plants along 24 small streams subjected to a range of anthropogenic disturbances in the boreal forest of northwestern Ontario, Canada. We included a total of 36 functional traits related to productivity, competitive ability, reproduction, disturbance tolerance, life history, and tolerance to habitat instability. Using nested ANOVA, we examined the response of diversity indices to disturbance and whether it followed the intermediate disturbance hypothesis (IDH) and varied with habitat stability. We found that, like species richness and diversity, functional richness and diversity reached peaks at moderate disturbance intensity; functional diversity followed the predictions of the IDH. Second, disturbance-habitat-stability coupling has very little effect on overall species and functional diversity, but the effect on particular life forms and functions may be significant. Since species richness and diversity patterns are context and system dependent, our findings should be most applicable to similar temperate riparian systems. [ABSTRACT FROM AUTHOR]

There is an increasing recognition that microplastics contamination in soils has become an important threat for terrestrial ecosystems, and can interact with drought. In addition, due to the increasingly serious environmental pollution and the destruction of the ozone layer, the UV-B radiation to the earth's surface has gradually increased. However, we currently have no information about potential effects of microplastics, UV-B, and drought on plant communities. In order to make up for the vacancy, we conducted an experiment with grassland plant communities. Polyester fiber microplastics (absent, present), UV-B (fully transparent polythene film, attenuating UV-B radiation), and soil water conditions (well-watered, drought) were applied in a fully factorial design. A plant community consisting of four indigenous species and one invasive species, co-occurring in the terrestrial ecosystem of the northern temperate zone was established, and we investigated the effects of microplastics, UV-B, drought and their interactions on plant functional traits and plant community structure. We found that shoot and root biomass decreased with drought but increased with microfibers, and drought significantly decreased specific leaf area at the community level. Physiological and biochemical indexes of individual species and plant community were affected by microfibers, UV-B, drought and their interaction to a varying degree. More importantly, five species were divided into three clusters along PC1 corresponding to individuals from G. longituba and P. depressa , B. bipinnata and M. sativa , plus G. parviflora, which indicated that at the same conditions, G. parviflora would occupy unique ecological niches that affect the growth of native species. Our research offers insights into the mechanisms of the coexistence of native and invasive plants, as well as the ecological consequences of microplastics and other environment factors on plant communities. [Display omitted] • Polyester fiber-microplastics increased height and shoot biomass for all plant species, especially invasive species G. parviflora. • Drought negatively affected height and shoot biomass for all plant species. • At the same conditions, G. parviflora would occupy a unique ecological niche and affect the growth of native species. [ABSTRACT FROM AUTHOR]

We propose a rapid sampling method to assess the functional composition of herbaceous plant communities without prior knowledge of the floristic composition. To determine the community-level value of traits (‘aggregated trait values’) for a plant community, a standardized population-centred method exists, but requires substantial manpower and reliable botanical knowledge. We tested an alternative method, the trait transect, using four subalpine pastures in the Beaufortain region (Northern French Alps) selected along a fertility gradient. We applied both methods to measure five commonly used ‘soft traits’ known to be responsive to soil nutrient availability: plant vegetative and reproductive height, specific leaf area, leaf dry matter and nitrogen contents. We tested whether the variation of these traits along the gradient detected with the population-centred method was also detected with the trait transect. Both methods detected expected trends in the traits in response to the fertility gradient. The trait transect method was as efficient as the population-centred method and is recommended as an appropriate tool for monitoring ecosystem changes in response to environmental conditions and management, especially in species-rich communities. [ABSTRACT FROM AUTHOR]

Question: Land-use change has a major impact on terrestrial plant communities by affecting fertility and disturbance. We test how particular combinations of plant functional traits can predict species responses to these factors and their abundance in the field by examining whether trade-offs at the trait level (fundamental trade-offs) are linked to trade-offs at the response level (secondary trade-offs). Location: Central French Alps. Methods: We conducted a pot experiment in which we characterized plant trait syndromes by measuring whole plant and leaf traits for six dominant species, originating from contrasting subalpine grassland types. We characterized their response to nutrient availability, shading and clipping. We quantified factors linked with different land usage in the field to test the relevance of our experimental treatments. Results: We showed that land management affected nutrient concentration in soil, light availability and disturbance intensity. We identified particular suites of traits linked to plant stature and leaf structure which were associated with species responses to these environmental factors. Leaf dry matter content separates fast and slow growing species. Height and lateral spread separated tolerant and intolerant species to shade and clipping. Discussion and Conclusion: Two fundamental trade-offs based on stature traits and leaf traits were linked to two secondary trade-offs based on response to fertilization shade and mowing. Based on these trade-offs, we discuss four different species strategies which could explain and predict species distributions and traits syndrome at community scale under different land-uses in subalpine grasslands. [ABSTRACT FROM AUTHOR]

The invasion of a target community by a non-indigenous plant species includes the stages of arrival,establishment and spread, which tend to depend on different characteristics of the invasive species and its context. While the mechanisms behind the invasion of highly disturbed ecosystems are well known, our understanding of the invasion process in undisturbed or weakly disturbed ecosystems is much more limited. Here we propose that, once a non-indigenous species has arrived to a new ecosystem and become established, the likelihood that it spreads, and thus becomes invasive, may depend on just one or very few characteristics, called 'triggering attributes' (TA). We propose that a TA is a vegetative or regenerative attribute discontinuously distributed in comparison to the resident community. This attribute allows the species to benefit from a resource that is permanently or temporarily unused by the resident community. We present an original study case and examples from the literature to illustrate our approach, and we also propose some ways to test it in different ecosystems. [ABSTRACT FROM AUTHOR]