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A growing number of studies have demonstrated that biodiversity is a strong and positive predictor of ecosystem temporal stability by simultaneously affecting multiple underlying mechanisms of stability, that is dominance, asynchrony and averaging effects. However, to date, no study has disentangled the relative role of these key mechanisms of stability in biodiversity experiments.We created a species richness gradient by mimicking a loss of rare species and assessed the role of species richness on community stability and, more importantly, quantified the relative role of three stabilizing mechanisms, that is dominance (stabilization due to stable dominants compared to the rest of the species in the community), asynchrony (stabilization due to temporal asynchrony between species), and averaging effects (pure effect of diversity) on community stability across a species richness gradient.We found that extreme species loss negatively impacted community stability, but just three species were enough to stabilize biomass production to a level similar to highly diverse communities. However, the similar stability of communities resulted from differing contributions from each stabilizing mechanism, depending on the community diversity. Since less abundant species were more temporally variable, species loss stabilized the populations of the remaining species. The loss of rare and subordinate species reduced the dominance and averaging effects, but increased the asynchrony effect. Hence, the asynchrony effect played a major role in the stability of species poor communities, while the averaging effect drove most of the stability of species rich communities. Overall, dominance played only a minor role, accounting for 5%–15% of the stabilization, while asynchrony and averaging effects were dominating forces contributing to ~85%–95% of the total stabilization.Synthesis. This study highlights the importance of biodiversity and roles of dominant and rare species for long‐term community stability and, for the first time, disentangles relative roles of dominance effect, asynchrony and averaging effect on community stability in a real‐world biodiversity experiment. [ABSTRACT FROM AUTHOR]

Aim: Identifying the drivers of ecological stability is critical for ensuring the maintenance of ecosystem functioning and services, particularly in a changing world. Different ecological mechanisms by which biological communities stabilize ecosystem functions (i.e. "stabilizing effects") have been proposed, yet with various theoretical expectations and debated conclusions. Here we propose a unified framework that aims at reconciling, and combining, different approaches to reliably test the strength of three stabilizing effects on the temporal constancy of ecosystem functions: the effects of (a) dominant species, (b) species asynchrony, and (c) diversity. Innovation: Compared to existing developments the approach allows, for the first time, disentangling these three stabilizing effects at the level of individual communities. So far this was not possible, and conclusions depended on indirect tests and comparative analyses across communities. We also propose a graphical representation of the relative contributions of the three stabilizing effects on a ternary plot, allowing us to easily compare communities sampled in various ecological contexts in a standardized space. Main conclusions: Our study answers the current need for a unified framework to link theoretical concepts on the temporal stability of ecological communities to data analysis. The present development promises flexible tests for a deeper understanding of the ecological stabilization of biodiversity and the relative importance of its components. [ABSTRACT FROM AUTHOR]

Question: Although leaf biomechanical properties have been identified as critical traits for plant‐herbivore interactions, their responses to grazing pressure have been poorly investigated. Intensification of rangeland management, associated with fertilization and an increase in grazing pressure, has been shown to favour fast‐growing species that can compensate for biomass losses due to grazing. According to the postulated trade‐off between resource acquisition and defence, it is often expected that acquisitive traits should be associated with low leaf mechanical resistance. Here we investigated the responses of two leaf biomechanical traits, and their underlying traits, to management intensification. Location: We used a long‐term experiment in a rangeland located in the Mediterranean region of Southern France, in which three treatments corresponding to different fertilizer inputs and sheep grazing pressures were established. Methods: We sampled 24 abundant graminoid and forb species. The responses of work to shear and force to tear to the treatments were tested together with those of growth‐related leaf traits (leaf mass per area, dry matter content). To better understand the observed patterns, we tested whether the difference between species' leaf biomechanics could be explained by morpho‐anatomical characteristics such as leaf thickness and density. Results: Consistent with the acquisition–defence trade‐off hypothesis, we found that graminoids from fertilized and intensely grazed areas had lower leaf resistance than those in ungrazed areas. However, no difference in leaf biomechanics was found in forbs despite a significant decrease in leaf mass per area and leaf dry matter content with management intensification. Consistent with this, we found no significant effect of morpho‐anatomical traits on either biomechanical trait in forbs. Conclusions: Our results suggest that the observed responses in graminoids result from phenotypic constraints between resource acquisition and biomechanical defence. However, these phenotypic constraints appeared to be released in forbs, questioning the idea of a universal relationship between these two functions. [ABSTRACT FROM AUTHOR]

Despite great progress in our understanding of the mechanisms governing ecosystem stability in local communities, we still lack knowledge at a larger spatial scale. Studying the stability of metacommunities requires assessing the temporal stability and synchrony of populations across space and organizational levels. Previous attempts to disentangle these effects have provided limited ecological interpretations, and conceptual improvements are needed to identify the underlying ecological processes.We propose an extended framework aiming at disentangling simultaneously the relative effects of population stability and different types of synchronies on metacommunity stability. We adapted previous methods of decomposing stability into a new set of indices associated with clearer ecological hypotheses. Particularly, we provide synchrony indices that are not affected by statistical properties of the metacommunity but focus on species responses to environment, demography and interactions. We applied this framework to a unique dataset describing the sorted biomass of individual plant populations, across 12 communities of a species‐rich meadow, and for 16 years. The communities were sampled in different treatments of fertilization and dominant removal to evaluate the effect of environmental heterogeneity on stability.We found higher stability at a larger spatial scale, mainly due to statistical averaging (portfolio effect). The variability of individual populations was an important determinant of the stability of the whole metacommunity. Consistent with the hypothesis of a common response to environmental conditions, we found that the fluctuations of populations were mostly synchronized (within and between species) at a large spatial scale and tended to destabilize the metacommunity. On the other hand, opposite fluctuations (anti‐synchrony) between populations occurred at the local scale, probably due to local species interactions.Synthesis. Our framework appears as a powerful tool to test how ecological processes occurring simultaneously at different spatial and organizational scales affect the stability of metacommunities. This study advances our ecological understanding of the processes underlying the stability of species‐rich environments. [ABSTRACT FROM AUTHOR]

The increasing use of artificial light at night has led to ecosystem exposure to light pollution worldwide. Aquatic ecosystems are particularly exposed, since lit road networks, urban development and industrial infrastructure are frequently located along river, lake, and sea shores. Although the negative effects of night‐time lighting on the physiology, behaviour, and life‐history traits of animals have been largely documented, there is a large knowledge gap about the responses of plants, especially regarding leaf functioning and resource‐management strategies. Some authors have proposed contrasting hypotheses of mechanistic responses to dim light at night in plants, but empirical results are still lacking.Based on field measurements of nocturnal irradiance in freshwater ecosystems located in peri‐urban areas, we performed a mesocosm experiment using three species of submerged aquatic plants. After 5 months of exposure to realistic dim light at night, four functional traits related to the resource management at the leaf level were measured.Artificial light at night had significant effects on the leaf physiology or chemistry, affecting their resource acquisition rate, but with different response intensities depending on the species. No effect was found on morphological or biomechanical traits for any of the studied species.These results support the hypothesis that plants could interpret dim light at night as a shaded environment and respond accordingly.We demonstrated that the effects of light at night on plants may have been underestimated in previous work. By modifying biotic interactions (e.g., competition and herbivory), these responses can have profound effects on community structure and ecosystem functioning. [ABSTRACT FROM AUTHOR]

The Metabolic Scaling Theory (MST), hypothesizes limitations of resource-transport networks in organisms and predicts their optimization into fractal-like structures. As a result, the relationship between population growth rate and body size should follow a cross-species universal quarter-power scaling. However, the universality of metabolic scaling has been challenged, particularly across transitions from bacteria to protists to multicellulars. The population growth rate of unicellulars should be constrained by external diffusion, ruling nutrient uptake, and internal diffusion, operating nutrient distribution. Both constraints intensify with increasing size possibly leading to shifting in the scaling exponent. We focused on unicellular algae Micrasterias. Large size and fractal-like morphology make this species a transitional group between unicellular and multicellular organisms in the evolution of allometry. We tested MST predictions using measurements of growth rate, size, and morphology-related traits. We showed that growth scaling of Micrasterias follows MST predictions, reflecting constraints by internal diffusion transport. Cell fractality and density decrease led to a proportional increase in surface area with body mass relaxing external constraints. Complex allometric optimization enables to maintain quarter-power scaling of population growth rate even with a large unicellular plan. Overall, our findings support fractality as a key factor in the evolution of biological scaling. [ABSTRACT FROM AUTHOR]

A recent analysis of variation in six major traits conducted on a large worldwide sample of vascular plant species showed that three‐quarters of trait variation was captured by a two‐dimensional global spectrum of plant form and function ("global spectrum" hereafter). We developed the PhenoSpace application, whose aim is to visualize and export the position of any individual/population/species in the phenotypic space of the global spectrum.PhenoSpace is a Shiny application that helps users to manipulate and visualize data pertaining to the global spectrum of plant form and function. It is freely accessible at the following URL: https://shiny.cefe.cnrs.fr/PhenoSpace/.PhenoSpace has three main functionalities. First, it allows users to visualize the phenotypic space of the global spectrum using different combinations of traits and growth forms. Second, trait data from any new user‐defined dataset can be projected onto the phenotypic space of the global spectrum, provided that at least two of the six traits are available. Finally, figures produced and loadings of the imported data on the PCA axes can be downloaded, allowing users to conduct further analyses.PhenoSpace fulfills the practical goal of positioning plants in the phenotypic space of the global spectrum, making it possible to compare trait variation at any level of organization against the worldwide background. This serves a major aim of comparative plant ecology, which is to put specific sets of individuals, populations or species into a broader context, facilitating comparison and synthesis of results across different continents and environments using relevant indicators of plant design and function. [ABSTRACT FROM AUTHOR]

Summary: Phenology, the study of seasonal timing of events in nature, plays a key role in the matching between organisms and their environment. Yet, it has been poorly integrated in trait‐based descriptions of the plant phenotype. Here, we focus on three phases of reproductive phenology – time of flowering, time of seed dispersal and duration of seed maturation – to test how these traits relate to other recognized dimensions of plant functioning.Traits describing reproductive phenology, together with reproductive plant height, seed mass, area of a leaf, and traits involved in leaf economics, were compiled for 139 species growing under Mediterranean climate conditions.Across all species, flowering time was positively related to reproductive height, while the duration of seed maturation was related to leaf economics. Relationships differed among growth forms, however: flowering time and reproductive height were related both in annuals and in herbaceous perennials, whereas the duration of seed maturation was related to seed mass only in annuals; no correlations were found for woody species.Phenology relates to other dimensions of plant functioning in a complex manner, suggesting that it should be considered as an independent dimension in the context of plant strategies. [ABSTRACT FROM AUTHOR]

Abstract: The phenology of organisms corresponds to the temporal match between the components of their life cycle and the seasonal distribution of resources and hazards. Flowering has been extensively studied to describe the reproductive phenology of plants, but in comparison, other key events for reproductive success such as the seed maturation period and the time of seed dispersal have been considerably less investigated. This study describes the temporal sequence of onset of flowering and seed dispersal, and the time necessary to mature seeds in 138 species growing in the strongly seasonal climate of Mediterranean southern France. Data for the three traits were compiled from several original surveys to characterize the reproductive phenology of 47 annual, 67 perennial herbaceous and 24 low stature woody species. The timing of these three phases was assessed in relation to local climatic conditions, and the degree to which they were coordinated was tested. All three phenological traits spanned a wide range of values from early spring to late summer. Annuals flowered slightly earlier than perennials but the largest difference between these groups was found for the seed maturation period, which was much shorter in annuals. This resulted in earlier dispersal dates in these species, which occurred before periods of high water deficit. Significant positive correlations were found between onset of flowering, onset of seed dispersal and seed maturation period. This suggests a consistent pattern of coordination between the different phases of reproductive phenology across species. Our results show that while the time slot for flowering appears restricted to periods with adequate temperature and water availability for most species, the seed maturation period and dispersal phase can occur during periods of substantial water deficit, at least for perennials. They also suggest that the different species can be arrayed along a fast‐slow continuum based on reproductive events, from early flowering species with short seed maturation and early dispersal to late flowering species with long seed maturation and late dispersal. Whether this relates to the postulated fast‐slow continuum identified for the functioning of vegetative organs is a promising avenue for future research. A plain language summary is available for this article. [ABSTRACT FROM AUTHOR]

Aims: Oligotrophic grasslands are habitats that host among the most diverse plant communities in Europe. Altering management regimes by either intensifying or ceasing management is known to decrease plant diversity. Yet, despite its importance for the recovery of plant communities after disturbances, little is known about whether seed banks are also affected by changes in management. Here, we investigate the effect of management practices on a meadow seed bank using a long‐term manipulative experiment. We focus on the response of the seed bank to the treatments, and the relationship between the seed bank and the vegetation response. Methods: The study was conducted in a species‐rich wet meadow. The experiment consists of a factorial combination of fertilization, mowing, and removal of the dominant species. After 20 years of management, the seed bank was sampled seasonally at two soil layer depths. Standing vegetation was recorded in June at the peak of vegetation. Results: All seed bank characteristics varied between soil layers. Mowing decreased seed density and diversity, while fertilization significantly affected the species composition. Dominant removal had no effect on the seed bank. While seed bank diversity was not correlated to vegetation diversity, individual species' responses to mowing and fertilization were positively correlated in the seed bank and the vegetation. Conclusions: Our results show that long‐term management influences the seed bank down to 10 cm of soil depth. Whereas mowing apparently reduced seed density and diversity, the effects of fertilization on these characteristics were harder to interpret. After 20 years, most species had concordant responses to both mowing and fertilization, indicating a low legacy of previous management regimes on the seed bank. Our study reveals that the intensification of grassland management has a profound effect on plant diversity by directly affecting plant communities and their seed‐bank‐driven recovery potential. [ABSTRACT FROM AUTHOR]

Abstract: The leaf economics spectrum (LES) describes covariation in traits relevant to carbon and nutrient economics across plant species, but much less is known about the relationship between the LES and leaf water economy. We propose an approach combining the measurement of two leaf traits related to water‐use economy, leaf carbon (δ13C) and oxygen (δ18O) isotopic composition, and the measurement of leaf morphological and nutrient traits to investigate the link between leaf carbon and nutrient economics and water use. We tested the relationships between leaf traits linked to carbon and nutrient use within the LES and water‐use traits using leaf δ18O as a proxy of stomatal conductance (gs) and δ13C as a proxy of intrinsic water‐use efficiency (WUEi) across 15 Mediterranean rangeland species grown in an irrigated common garden and in a natural rangeland in Southern France. The target species spanned a wide range of variation in leaf morphological and nutrient trait values and a wide range of leaf δ18O and δ13C values. Principal component analysis revealed multiple associations among leaf morphology, nutrients and isotopic composition, with the first axis alone explaining 56.0% of the total variation across species. Leaf δ18O and δ13C covaried with leaf morphology and leaf nutrient concentrations along a single resource‐use axis. Species with high leaf δ18O and δ13C (low gs and high WUEi) exhibited a resource‐conservative strategy (high leaf dry matter content, low leaf N, P and K), whereas species with low leaf δ18O and δ13C (high gs and low WUEi) showed a more resource‐acquisitive strategy (high specific leaf area and leaf N, P and K). These leaf trait syndromes and resource‐use strategies were strongly conserved across sites with contrasting environmental conditions, indicating that foliar δ18O and δ13C can be included as an integral part of the LES for this set of rangeland species. Overall, the data suggest a tight coupling and coordination between water, carbon and nutrient‐use strategies across herbaceous plant species. A dual δ18O and δ13C isotope approach combined with LES trait measurements is a promising tool to more comprehensively assess the diversity of resource‐use strategies among coexisting plant species. A plain language summary is available for this article. [ABSTRACT FROM AUTHOR]

Clarifying the functional consequences of intraspecific trait variability in response to interacting trophic levels would provide a significant improvement in our understanding of above‐ground–below‐ground linkages. In particular, the effects of grazing on plant traits may translate into altered litter quality, with potentially important consequences for litter‐feeding decomposers. Plant and litter variability in response to grazing is expected to depend on soil fertility levels, with tolerance and defensive strategies more commonly expressed on fertile and poorer soils, respectively. However, how grazing and fertility interactively alter litter quality and palatability to detritivores has not been explored yet.We conducted a cafeteria experiment with three common millipede (Diplopoda) species feeding on leaf litter from two plant species, the grass Bromopsis erecta and the forb Potentilla verna. Each millipede was offered a binary choice between litter types produced by the same plant species, but sampled in plots with distinct herbivory and fertilization status: litter originating from grazed areas or from 1‐year sheep exclosures, both in native areas and in adjacent paddocks that received chemical N and P fertilization, as well as litter from a 25‐year sheep exclosures in the native area.We found that fertilization and herbivore exclusion interactively affected Bromopsis litter quality and palatability, whereas Potentilla was much less affected. Bromopsis litter palatability was not affected by grazing when litter was collected in native plots, except for the long‐term exclosure which led to low palatability. In contrast, and in line with our expectations, herbivory was associated with much higher palatability in fertilized plots. The changes in palatability were associated with important alterations of litter quality.Overall, our study demonstrates that intraspecific variation in litter can have profound consequences for soil functioning. It emphasizes the role of grazing as a key, but plant species‐specific factor controlling litter intraspecific variability, and its complex interaction with soil fertility level. Moreover, our results advocate for a better understanding of the response of the different organisms involved in the decomposition process, in particular litter‐feeding macro‐detritivores. We encourage future studies aiming at disentangling the various and complex relationships between above‐ground processes such as herbivory and soil functioning. Plain Language Summary [ABSTRACT FROM AUTHOR]

Background and aims The CSR classification categorizes plants as stress tolerators (S), ruderals (R) and competitors (C). Initially proposed as a general framework to describe ecological strategies across species, this scheme has recently been used to investigate the variation of strategies within species. For instance, ample variation along the S–R axis was found in Arabidopsis thaliana, with stress-tolerator accessions predominating in hot and dry regions, which was interpreted as a sign of functional adaptation to climate within the species. Methods In this study the range of CSR strategies within A. thaliana was evaluated across 426 accessions originating from North Africa to Scandinavia. A position in the CSR strategy space was allocated for every accession based on three functional traits: leaf area, leaf dry matter content (LDMC) and specific leaf area (SLA). Results were related to climate at origin and compared with a previous study performed on the same species. Furthermore, the role of natural selection in phenotypic differentiation between lineages was investigated with Q ST– F STcomparisons, using the large amount of genetic information available for this species. Key Results Substantial variation in ecological strategies along the S–R axis was found in A. thaliana. By contrast with previous findings, stress-tolerator accessions predominated in cold climates, notably Scandinavia, where late flowering was associated with traits related to resource conservation, such as high LDMC and low SLA. Because of trait plasticity, variations in CSR classification in relation to growth conditions were also observed for the same genotypes. Conclusions There is a latitudinal gradient of ecological strategies in A. thaliana as a result of within-species adaptation to climate. Our study also underlines the importance of growth conditions and of the methodology used for trait measurement, notably age versus stage measurement, to infer the strength and direction of trait–environment relationships. This highlights the potential and limitations of the CSR classification in explaining functional adaptation to the environment. [ABSTRACT FROM AUTHOR]

With the rise of large herbivore populations in most northern hemisphere forests, browsing is becoming an increasingly important driver of forest regeneration dynamics. Among other processes affecting the regeneration, the concept of plant-herbivore feedback loops holds that browsed saplings are more subject to subsequent herbivory. This phenomenon is interpreted as a consequence of compensatory growth following browsing since fast growth is generally associated with higher digestibility and lower defense against herbivores. However, studies linking browsing-induced trait variations to subsequent attractiveness to herbivores are still lacking, especially in the forest context. In this study, we experimentally examine the existence of a feedback loop between oak (Quercus robur L.) and roe deer (Capreolus capreolus) and investigate its underlying morphological and chemical traits. We simulated single and repeated roe deer browsing on nursery-grown oak saplings and measured the changes in sapling height growth, lateral branching, leaf traits and winter shoot traits over two years. We conducted winter feeding trials with tame roe deer one year after the first treatment to test the effect of simulated browsing on sapling attractiveness. Simulated browsing reduced sapling height growth but had no effect on branching. Simulated browsing had no effect on leaf traits after half a year, but decreased the phenolic content and increased the fiber content of winter shoots the following winter. Contrary to our predictions, roe deer preferentially browsed control saplings over saplings previously browsed. After two years, repeated browsing promoted fast carbon acquisition leaf traits (high chlorophyll, high specific leaf area and low fiber content), reduced leaf phenolic content and increased leaf digestibility. We showed that a reduction in 1-year-old oak sapling height growth following browsing, combined with increased structural defense at the expense of chemical defense in winter shoots the following winter, was correlated with reduced browsing pressure, thereby challenging the feedback loop hypothesis. However, we also demonstrated that repeated browsing promoted fast carbon acquisition leaf traits in 2.5-year-old saplings, which tend to support the existence of a feedback loop on older and more intensively browsed saplings. As such, our study provides empirical evidence that morphological and physiological trait responses to browsing influence oak sapling attractiveness, but that the direction and magnitude of this effect depend on the ontogenic stage of the sapling and on the number of browsing events. • We examine the morphological and chemical response of oak saplings to browsing. • Browsing reduces sapling height growth and modifies shoots chemical composition. • We show with feeding trials that roe deer prefers unbrowsed saplings. • Oak trait responses to browsing decrease the probability of subsequent herbivory. [ABSTRACT FROM AUTHOR]