Châtenoy-le-Royal, France
Châtenoy-le-Royal, France

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Borgy B.,CNRS Center of Evolutionary and Functional Ecology | Violle C.,CNRS Center of Evolutionary and Functional Ecology | Choler P.,French National Center for Scientific Research | Garnier E.,CNRS Center of Evolutionary and Functional Ecology | And 15 more authors.
Global Ecology and Biogeography | Year: 2017

Aim: The characterization of trait-environment relationships over broad-scale gradients is a critical goal for ecology and biogeography. This implies the merging of plot and trait databases to assess community-level trait-based statistics. Potential shortcomings and limitations of this approach are that: (i) species traits are not measured where the community is sampled and (ii) the availability of trait data varies considerably across species and plots. Here we address the effect of trait data representativeness [the sampling effort per species and per plot] on the accuracy of (i) species-level and (ii) community-level trait estimates and (iii) the consequences for the shape and strength of trait-environment relationships across communities. Innovation: We combined information existing in databases of vegetation plots and plant traits to estimate community-weighted means [CWMs] of four key traits [specific leaf area, plant height, seed mass and leaf nitrogen content per dry mass] in permanent grasslands at a country-wide scale. We propose a generic approach for systematic sensitivity analyses based on random subsampling and data reduction to address the representativeness of incomplete and heterogeneous trait information when exploring trait-environment relationships across communities. Main conclusions: The accuracy of the CWMs was little affected by the number of individual trait values per species [NIV] but strongly affected by the cover proportion of species with available trait values [PCover]. A PCover above 80% was required for all four traits studied to obtain an estimation bias below 5%. Our approach therefore provides more conservative criteria than previously proposed. Restrictive criteria on both NIV and PCover primarily excluded communities in harsh environments, and such reduction of the sampled gradient weakened trait-environment relationships. These findings advocate systematic measurement campaigns in natural environments to increase species coverage in global trait databases, with special emphasis on species occurring in under-sampled and harsh environmental conditions. © 2017 John Wiley & Sons Ltd.


Violle C.,CNRS Center of Evolutionary and Functional Ecology | Choler P.,University Grenoble Alpes | Choler P.,French National Center for Scientific Research | Borgy B.,CNRS Center of Evolutionary and Functional Ecology | And 21 more authors.
Science of the Total Environment | Year: 2015

The effect of biodiversity on ecosystem functioning has been widely acknowledged, and the importance of the functional roles of species, as well as their diversity, in the control of ecosystem processes has been emphasised recently. However, bridging biodiversity and ecosystem science to address issues at a biogeographic scale is still in its infancy. Bridging this gap is the primary goal of the emerging field of functional biogeography. While the rise of Big Data has catalysed functional biogeography studies in recent years, comprehensive evidence remains scarce. Here, we present the rationale and the first results of a country-wide initiative focused on the C3 permanent grasslands. We aimed to collate, integrate and process large databases of vegetation relevés, plant traits and environmental layers to provide a country-wide assessment of ecosystem properties and services which can be used to improve regional models of climate and land use changes. We outline the theoretical background, data availability, and ecoinformatics challenges associated with the approach and its feasibility. We provide a case study of upscaling of leaf dry matter content averaged at ecosystem level and country-wide predictions of forage digestibility. Our framework sets milestones for further hypothesis testing in functional biogeography and earth system modelling. © 2015 Elsevier B.V.


PubMed | Max Planck Institute for Biogeochemistry, CNRS Mediterranean Institute for Biodiversity and Ecology Marine and Continental, French National Institute for Agricultural Research, Federation des Conservatoires Botaniques Nationaux and 6 more.
Type: | Journal: The Science of the total environment | Year: 2015

The effect of biodiversity on ecosystem functioning has been widely acknowledged, and the importance of the functional roles of species, as well as their diversity, in the control of ecosystem processes has been emphasised recently. However, bridging biodiversity and ecosystem science to address issues at a biogeographic scale is still in its infancy. Bridging this gap is the primary goal of the emerging field of functional biogeography. While the rise of Big Data has catalysed functional biogeography studies in recent years, comprehensive evidence remains scarce. Here, we present the rationale and the first results of a country-wide initiative focused on the C3 permanent grasslands. We aimed to collate, integrate and process large databases of vegetation relevs, plant traits and environmental layers to provide a country-wide assessment of ecosystem properties and services which can be used to improve regional models of climate and land use changes. We outline the theoretical background, data availability, and ecoinformatics challenges associated with the approach and its feasibility. We provide a case study of upscaling of leaf dry matter content averaged at ecosystem level and country-wide predictions of forage digestibility. Our framework sets milestones for further hypothesis testing in functional biogeography and earth system modelling.


Boulangeat I.,CNRS Alpine Ecology Laboratory | Georges D.,CNRS Alpine Ecology Laboratory | Dentant C.,Parc National des Ecrins | Bonet R.,Parc National des Ecrins | And 4 more authors.
Ecography | Year: 2014

Vegetation is a key driver of ecosystem functioning (e.g. productivity and stability) and of the maintenance of biodiversity (e.g. creating habitats for other species groups). While vegetation sensitivity to climate change has been widely investigated, its spatio-temporally response to the dual effects of land management and climate change has been ignored at landscape scale. Here we use a dynamic vegetation model called FATE-HD, which describes the dominant vegetation dynamics and associated functional diversity, in order to anticipate vegetation response to climate and land-use changes in both short and long-term perspectives. Using three contrasted management scenarios for the Ecrins National Park (French Alps) developed in collaboration with the park managers, and one regional climate change scenario, we tracked the dynamics of vegetation structure (forest expansion) and functional diversity over 100 yr of climate change and a further 400 additional years of stabilization. As expected, we observed a slow upward shift in forest cover distribution, which appears to be severely impacted by pasture management (i.e. maintenance or abandonment). The time lag before observing changes in vegetation cover was the result of demographic and seed dispersal processes. However, plant diversity response to environmental changes was rapid. After land abandonment, local diversity increased and spatial turnover was reduced, whereas local diversity decreased following land use intensification. Interestingly, in the long term, as both climate and management scenarios interacted, the regional diversity declined. Our innovative spatio-temporally explicit framework demonstrates that the vegetation may have contrasting responses to changes in the short and the long term. Moreover, climate and land-abandonment interact extensively leading to a decrease in both regional diversity and turnover in the long term. Based on our simulations we therefore suggest a continuing moderate intensity pasturing to maintain high levels of plant diversity in this system. © 2014 The Authors.


Pellissier L.,University of Lausanne | Brathen K.A.,University of Tromsø | Vittoz P.,University of Lausanne | Yoccoz N.G.,University of Tromsø | And 9 more authors.
Global Ecology and Biogeography | Year: 2013

Aim: Understanding the stability of realized niches is crucial for predicting the responses of species to climate change. One approach is to evaluate the niche differences of populations of the same species that occupy regions that are geographically disconnected. Here, we assess niche conservatism along thermal gradients for 26 plant species with a disjunct distribution between the Alps and the Arctic. Location: European Alps and Norwegian Finnmark. Methods: We collected a comprehensive dataset of 26 arctic-alpine plant occurrences in two regions. We assessed niche conservatism through a multispecies comparison and analysed species rankings at cold and warm thermal limits along two distinct gradients corresponding to (1) air temperatures at 2m above ground level and (2) elevation distances to the tree line (TLD) for the two regions. We assessed whether observed relationships were close to those predicted under thermal limit conservatism. Results: We found a weak similarity in species ranking at the warm thermal limits. The range of warm thermal limits for the 26 species was much larger in the Alps than in Finnmark. We found a stronger similarity in species ranking and correspondence at the cold thermal limit along the gradients of 2-m temperature and TLD. Yet along the 2-m temperature gradient the cold thermal limits of species in the Alps were lower on average than those in Finnmark. Main conclusion: We found low conservatism of the warm thermal limits but a stronger conservatism of the cold thermal limits. We suggest that biotic interactions at the warm thermal limit are likely to modulate species responses more strongly than at the cold limit. The differing biotic context between the two regions is probably responsible for the observed differences in realized niches. © 2013 John Wiley & Sons Ltd.


PubMed | CNRS Alpine Ecology Laboratory, Parc National des Ecrins, Conservatoire Botanique National Alpin and Swiss Federal Institute of forest
Type: Journal Article | Journal: Ecography | Year: 2015

Vegetation is a key driver of ecosystem functioning (


Bonnet V.,Conservatoire Botanique National Alpin | Fort N.,Conservatoire Botanique National Alpin | Dentant C.,Parc National des Ecrins | Bonet R.,Parc National des Ecrins | And 3 more authors.
Acta Botanica Gallica | Year: 2015

There is an increasing need for data on the patterns of population changes for rare species at the regional, national and European scales in the context of the Natura 2000 reporting on the state of species conservation. This reporting requires the use of the same protocol over a whole region or country with the major constraint that it has to be shared by a large array of conservations and monitoring structures. The protocol has therefore to be both precise and reproducible but also simple enough to be used over a large number of sites and years, and has moreover to be accepted by various conservation structures.In this aim, the Alps-Ain flora conservation network (Réseau Alpes-Ain de Conservation de la Flore), a network composed of flora conservation stakeholders for 2 regions, Provence-Alpes-Côte dAzur and Rhône-Alpes, set up a series of nested protocols to monitor populations at different spatial scales (levels). Each monitoring level is set up to answer to a specific aim and corresponds to a protocol shared by all the network actors. The first level, detailed below, is defined for the regional scale ("territory" level) with the site as observation unit. The second level aims at identifying if in a specific site ("station") a population is stable, expanding or regressing and if natural or anthropic factors can explain this dynamics. The observation unit is a plot or a transect and the variables measured are frequencies or numbers and environmental parameters. The third level is an individual-based survey ("individu") and aims at understanding the demographic processes affecting a population. The observation unit is here the individual plant. The link between the 3 levels is described in Figure 1.The "territory" level protocol was developed over several years of discussions and in situ tests on several species (Table 1). Its aim is to identify increases or decreases of species size at the scale of the region. The variables used for this monitoring are simple and easily reproducible: area of presence and frequency. During the process, we realized that even a simple protocol could not be applied to a large range of species. We therefore propose some variations on a common methodological base, depending on the biology of the species (longevity, clonality, dormancy, size of individuals.). An originality of the protocol is to note the non-detection of the species in a given point at a given time to be able to document the expansion or the regression of the species in the site. A first step therefore consists in defining the zone in which the species will be looked for, the prospection zone (ZP). This zone should correspond as much as possible to the potential habitat of the species and has to remain constant over time. Within this zone, the area of presence (AP) is determined using the envelope formed by the GPS points where the species is found. Population size is then estimated as the frequency of occurrence by contact-points along at least two transects positioned so as to take into account the environmental heterogeneity of the site (see Figure 1). For species that have very variable population sizes and distributions, the transects should be representative of the AP; for species with very stable populations, we recommend fixed transects to reduce year-to-year and spatial variations, however managers are free to choose the location of the transects. At least 100 points are taken for each transect in order to have a robust estimate of the frequency of occurrence. For species with low ground cover, we suggest replacing the contact-point by contact-areas, i.e. small plots positioned similarly to the points along the transects. The areas of the plots have to be decided in advance and should not change over time. The aim is to avoid extreme frequency values (close to 0 or 1) in order to be able to detect an increase or a decrease in population size. Each prospection zone corresponds to one data point. At the regional scale, the population is represented by the ensemble of the ZPs. To have a good estimate of the population size and its dynamics, the ZPs should correspond to a random or a stratified sample of all the existing sites. This is however difficult and in practice, the ZPs of the survey are the ones for which an organism can commit itself. The RAACF then has to make sure that the sample of ZPs is representative of the species distribution. The frequency of the survey depends on the biological characteristics of the species. For perennial species we suggest a time step of 3 to 5 years in the absence of catastrophic events. For annual or dormant species, the survey should be performed over 3-5 consecutive years in order to have a reliable estimate of AP and size and to smooth out the inter-annual (normal) fluctuations, and then repeated 3-5 years later. A web-service database was developed by the network to ensure the aggregation of the data. This method is a practical answer to the EU requirements in terms of assessment of populations of plant species in the framework of the EU Habitats Directive (Council Directive 92/43/EEC). © 2014 © 2014 Société botanique de France.


PubMed | University Grenoble Alpes and Conservatoire Botanique National Alpin
Type: Journal Article | Journal: PloS one | Year: 2016

Climatic niche shifts have been documented in a number of invasive species by comparing the native and adventive climatic ranges in which they occur. However, these shifts likely represent changes in the realized climatic niches of invasive species, and may not necessarily be driven by genetic changes in climatic affinities. Until now the role of rapid niche evolution in the spread of invasive species remains a challenging issue with conflicting results. Here, we document a likely genetically-based climatic niche expansion of an annual plant invader, the common ragweed (Ambrosia artemisiifolia L.), a highly allergenic invasive species causing substantial public health issues. To do so, we looked for recent evolutionary change at the upward migration front of its adventive range in the French Alps. Based on species climatic niche models estimated at both global and regional scales we stratified our sampling design to adequately capture the species niche, and localized populations suspected of niche expansion. Using a combination of species niche modeling, landscape genetics models and common garden measurements, we then related the species genetic structure and its phenotypic architecture across the climatic niche. Our results strongly suggest that the common ragweed is rapidly adapting to local climatic conditions at its invasion front and that it currently expands its niche toward colder and formerly unsuitable climates in the French Alps (i.e. in sites where niche models would not predict its occurrence). Such results, showing that species climatic niches can evolve on very short time scales, have important implications for predictive models of biological invasions that do not account for evolutionary processes.


Meynard C.N.,Montpellier SupAgro | Lavergne S.,CNRS Alpine Ecology Laboratory | Boulangeat I.,CNRS Alpine Ecology Laboratory | Garraud L.,Conservatoire Botanique National Alpin | And 3 more authors.
Journal of Biogeography | Year: 2013

Aim: Metacommunity theories attribute different relative degrees of importance to dispersal, environmental filtering, biotic interactions and stochastic processes in community assembly, but the role of spatial scale remains uncertain. Here we used two complementary statistical tools to test: (1) whether or not the patterns of community structure and environmental influences are consistent across resolutions; and (2) whether and how the joint use of two fundamentally different statistical approaches provides a complementary interpretation of results. Location: Grassland plants in the French Alps. Methods: We used two approaches across five spatial resolutions (ranging from 1 km × 1 km to 30 km × 30 km): variance partitioning, and analysis of metacommunity structure on the site-by-species incidence matrices. Both methods allow the testing of expected patterns resulting from environmental filtering, but variance partitioning allows the role of dispersal and environmental gradients to be studied, while analysis of the site-by-species metacommunity structure informs an understanding of how environmental filtering occurs and whether or not patterns differ from chance expectation. We also used spatial regressions on species richness to identify relevant environmental factors at each scale and to link results from the two approaches. Results: Major environmental drivers of richness included growing degree-days, temperature, moisture and spatial or temporal heterogeneity. Variance partitioning pointed to an increase in the role of dispersal at coarser resolutions, while metacommunity structure analysis pointed to environmental filtering having an important role at all resolutions through a Clementsian assembly process (i.e. groups of species having similar range boundaries and co-occurring in similar environments). Main conclusions: The combination of methods used here allows a better understanding of the forces structuring ecological communities than either one of them used separately. A key aspect in this complementarity is that variance partitioning can detect effects of dispersal whereas metacommunity structure analysis cannot. Moreover, the latter can distinguish between different forms of environmental filtering (e.g. individualistic versus group species responses to environmental gradients). © 2013 Blackwell Publishing Ltd.


Boulangeat I.,CNRS Alpine Ecology Laboratory | Lavergne S.,CNRS Alpine Ecology Laboratory | Van Es J.,Conservatoire Botanique National Alpin | Garraud L.,Conservatoire Botanique National Alpin | Thuiller W.,CNRS Alpine Ecology Laboratory
Journal of Biogeography | Year: 2012

Aim Species specialization, which plays a fundamental role in niche differentiation and species coexistence, is a key biological trait in relation to the responses of populations to changing environments. Species with a limited niche breadth are considered to experience a higher risk of extinction than generalist species. This work aims to measure the degree of specialization in the regional flora of the French Alps and test whether species specialization is related to species rarity and ecological characteristics. Location This study was conducted in the French Alps region, which encompasses a large elevational gradient over a relatively limited area (26,000km 2). Methods Specialization was estimated for approximately 1200 plant species found in the region. Given the inherent difficulty of pinpointing the critical environmental niche axes for each individual species, we used a co-occurrence-based index to estimate species niche breadths (specialization index). This comprehensive measurement included crucial undetermined limiting niche factors, acting on both local and regional scales, and related to both biotic and abiotic interactions. The specialization index for each species was then related to a selection of plant typologies such as Grime strategies and Raunkiaer life-forms, and to two measurements of plant rarity, namely regional area of occupancy and local abundance. Results Specialist species were mainly found in specific and harsh environments such as wetlands, cold alpine habitats and dry heathlands. These species were usually geographically restricted but relatively dominant in their local communities. Although none of the selected traits were sufficient predictors of specialization, pure competitors were over-represented amongst generalist species, whereas stress-tolerant species tended to be more specialized. Main conclusions Our results suggest that co-occurrence-based indices of niche breadth are a satisfactory method for inferring plant specialization using large species samples across very heterogeneous environments. Our results are an empirical validation of the tolerance-dominance trade-off and also provide interesting insights into the long-standing question of which biological properties characterize species with narrow niche breadth that are potentially threatened by global changes in the environment. © 2011 Blackwell Publishing Ltd.

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