Résumé
Background: The tussock grass Festuca paniculata can become strongly dominant in subalpine grasslands after cessation of mowing. The depletion of water-soluble carbohydrate (WSC) reserves has been suggested as a mechanism by which mowing can contain this species. By affecting plant physiology and especially by favouring WSC accumulation, extreme summer weather (i.e. exceptionally hot and dry) could however counterbalance the effects of mowing on WSC reserves in F. paniculata. The relevance of this hypothesis needs to be tested in the current context of climate and land-use changes. Aims: We investigated (1) the physiological mechanisms that control the growth of F. paniculata, (2) how they are affected by mowing and (3) whether extreme summer heat and drought could influence physiological mechanisms and thereby the ecological response of F. paniculata to mowing.
Methods: In a field experiment we manipulated weather and mowing during two summers. For current summer weather (W0), ambient temperature was unchanged and precipitation was adjusted on the past 30-year average. Extreme summer weather (W+) corresponded to a seasonal change (+1◦C, –80% in precipitation compared to W0) and a three-week heatwave (+4.3◦C) in the first year. In addition, vegetation was either mown at 5 cm in late summer (M) or left unmown (U). Concentrations and absolute contents of WSC contained in tiller bases, leaf nitrogen concentration (LNC), vegetative multiplication, plant growth and leaf senescence were measured from one to four times, depending on the variable considered, throughout the summer of the second year of the experiment.
Results: As compared to the unmown treatment, late-summer mowing decreased tillering, tussock size and LNC, regardless of the summer weather treatment. However, it depleted WSC pools, including fructans, only under current summer weather (W0).
Conclusions: These results suggest that extreme summer heat and drought could alleviate the sensitivity of F. paniculata to mowing. They raise the question of the consequences of recurrent summer extremes for conservation management in subalpine grasslands.
Auteurs, date et publication :
Auteurs Marie-Lise Benot , Patrick Saccone , Rachel Vicente , Emmanuelle Pautrat , Annette Morvan-Bertrand , Marie-Laure Decau , Karl Grigulis , Marie-Pascale Prud'homme , Sandra Lavorel
Publication : Plant Ecology & Diversity
Date : 2025
Volume : 6
Issue : 3-4
Pages : 393-404
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Land use and spatial patterns which reflect social-ecological legacies control ecosystem service (ES) supply. Yet, temporal changes in ES bundles associated with land use change are little studied. We developed original metrics to quantify synchronous historical variations in spatial patterns of land use and ES supply capacity, and demonstrated their use for two mountain grassland landscapes. Consistent with other European mountains, land use dynamics from the nineteenth century until the mid-twentieth century resulted in increased landscape heterogeneity, followed by homogenisation. In the persistently grassy landscape of Lautaret in France, landscape multifunctionality—the provision of multiple ES—coincided with greatest landscape heterogeneity and within-patch diversity in ecosystem services in the 1950–1970s. In the more complex Austrian landscape, where since the nineteenth century intensive production has concentrated in the valley and steep slopes have been abandoned, grassland landscape-level multifunctionality and spatial heterogeneity across grasslands have decreased. Increasing spatial heterogeneity across grasslands until the 1970s was paralleled at both sites by increasing fine-grained spatial variability for individual ES, but subsequent landscape simplification has promoted coarse-grained ES patterns This novel analysis of landscape-scale turnover highlighted how spatial patterns for individual ES scale to multiple grassland ES, depending on the nature of land use spatial variability. Under current socio-economic trends, sustaining or re-establishing fine-grained landscapes is often not feasible, thus future landscape planning and policies might focus on managing landscape and regional-scale multifunctionality. Also, the trends towards decreasing cultural ES and increasing regulating ES suggest a contradiction with current social demand and regional policies.
Auteurs, date et publication :
Auteurs Sandra Lavorel , Karl Grigulis , Georg Leitinger , Marina Kohler , Uta Schirpke , Ulrike Tappeiner
Publication : Regional Environmental Change
Date : 2017
Volume : 17
Issue : 8
Pages : 2251-2264
Catégorie(s)
#CNRS #Lautaret #UGARésumé
To ensure their quality of life, people adapt to multiple changes by maintaining or transforming the structure and functions of their socio-ecological systems (SES). A better understanding of mechanisms underpinning SES adaptation, especially the contribution of changes in human–nature interactions, is crucial to facilitate adaptation to future challenges. Using a chronosystemic timeline and based on literature, archives and local knowledge of inhabitants, we explored the past trajectory of a mountain SES (Pays de la Meije, French Alps) since 1900 by analysing drivers, impacts and responses. We hypothesised that adaptation has occurred through changes in the co-production of nature’s contributions to people (NCP). We identified four historical periods of combined changes in agriculture and tourism with associated changes in NCP. Results show which and how drivers of changes have influenced NCP co-production, how NCP have been mobilised in adaptive responses and how human and natural capitals involved in NCP co-production have been reconfigured for adaptation. We show that drivers of change have been mainly exogenous and out of the control of local actors, like public policies, markets and consumption patterns. These drivers can directly impact the capitals involved in NCP co-production like amount of workforce, knowledge or skills, creating not only threats but also opportunities for the livelihood of the local community. Depending on the intensity of capital reconfiguration and the type of NCP involved, adaptive responses range from resistance to transformation of the governance system and socio-economic sectors. This analysis highlights existing path dependencies that could hinder future adaptation.
Auteurs, date et publication :
Auteurs Enora Bruley , Bruno Locatelli , François Vendel , Agnès Bergeret , Nicolas Elleaume , Julia Grosinger , Sandra Lavorel
Publication : Regional Environmental Change
Date : 2021
Volume : 21
Issue : 2
Pages : 34
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Small mammal population outbreaks are one of the consequences of socio-economic and technological changes in agriculture. They can cause important economic damage and generally play a key role in food webs, as a major food resource for predators. The fossorial form of the water vole, Arvicola terrestris, was unknown in the Haute Romanche Valley (French Alps) before 1998. In 1998, the first colony was observed at the top of a valley and population spread was monitored during 12 years, until 2010. Spread occurred as a high population density wave. Based on farming history (1810–2003, 193 years) and spatio-temporal analysis of crop rotations, our study indicates that this water vole population outbreak has been promoted by the presence of grassland corridors that increase hayfield connectivity. These corridors appeared as a result of the conversion of cropped fields to hay meadows where water vole outbreaks have occurred. Spatial mosaic management for grasslands with decreasing spatial connectedness should be considered to prevent vole outbreak risks and promote biodiversity.
Auteurs, date et publication :
Auteurs Guillaume Halliez , François Renault , Eric Vannard , Gilles Farny , Sandra Lavorel , Patrick Giraudoux
Publication : Agriculture, Ecosystems & Environment
Date : 2025
Volume : 212
Pages : 198-206
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Understanding the influence of the environment on the functional structure of ecological communities is essential to predict the response of biodiversity to global change drivers. Ecological theory suggests that multiple environmental factors shape local species assemblages by progressively filtering species from the regional species pool to local communities. These successive filters should influence the various components of community functional structure in different ways. In this paper, we tested the relative influence of multiple environmental filters on various metrics of plant functional trait structure (i.e. ‘community weighted mean trait’ and components of functional trait diversity, i.e. functional richness, evenness and divergence) in 82 vegetation plots in the Guisane Valley, French Alps. For the 211 sampled species we measured traits known to capture key aspects of ecological strategies amongst vascular plant species, i.e. leaf traits, plant height and seed mass (LHS). A comprehensive information theory framework, together with null model based resampling techniques, was used to test the various environmental effects. Particular community components of functional structure responded differently to various environmental gradients, especially concerning the spatial scale at which the environmental factors seem to operate. Environmental factors acting at a large spatial scale (e.g. temperature) were found to predominantly shape community weighted mean trait values, while fine-scale factors (topography and soil characteristics) mostly influenced functional diversity and the distribution of trait values among the dominant species. Our results emphasize the hierarchical nature of ecological forces shaping local species assemblage: large-scale environmental filters having a primary effect, i.e. selecting the pool of species adapted to a site, and then filters at finer scales determining species abundances and local species coexistence. This suggests that different components of functional community structure will respond differently to environmental change, so that predicting plant community responses will require a hierarchical multi-facet approach.
Auteurs, date et publication :
Auteurs Francesco de Bello , Sandra Lavorel , Sébastien Lavergne , Cécile H. Albert , Isabelle Boulangeat , Florent Mazel , Wilfried Thuiller
Publication : Ecography
Date : 2025
Volume : 36
Issue : 3
Pages : 393-402
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Herbivores can have contrasted impacts on litter quality and litter decomposition, through an alteration of leaf chemistry and leaf senescence. Depending on the context, herbivores can induce defensive secondary compounds and thus slow down litter decomposition or accelerate decomposition by short-cutting nutrient resorption. Almost nothing is known for grasses, which contain smaller amounts of secondary compounds than forbs and trees. Because grasses span a gradient from exploitative species having a low C : N ratio and induced defences, to conservative species having a high C : N ratio and constitutive defences, we hypothesize that the litter dynamics of functionally contrasted grasses may be differentially altered by herbivores. In a mesocosm experiment, we assessed the litter decomposition rate of two subalpine grasses, the more exploitative Dactylis glomerata and the conservative Festuca paniculata, in the presence of two grasshopper species, Chorthippus scalaris and Euthystira brachyptera. We hypothesized that decomposition patterns depending on grass species and herbivory could be explained by the C : N ratio and the total phenolic content of fresh, senescent and decomposed leaves. Herbivory by grasshoppers induced the accumulation of phenolics in the fresh leaves of D. glomerata, but most of these compounds were lost during senescence. The decomposition rate of D. glomerata senescent leaves did not depend on herbivory, phenolics and N content or C : N ratio. In contrast, herbivory did not induce any phenolic accumulation in the grazed leaves of F. paniculata, but during senescence, phenolics disappeared in greater proportions in grazed leaves than in ungrazed leaves, probably due to the physical alteration of grazed leaves. Herbivory slowed down the decomposition rate of F. paniculata, which was correlated to the phenolic concentration of senescent leaves, but not to the C : N ratio or N content. Herbivory by grasshoppers differentially altered the litter decomposition rate of the two functionally contrasted grasses, having no effect on D. glomerata and slowing down F. paniculata. Thus, the combination of chemical and physical modifications of leaves by grazing and their interaction with grass traits may have either accelerating or decelerating effects on litter decomposition, with potentially complex outcomes at the ecosystem level.
Auteurs, date et publication :
Auteurs Sébastien Ibanez , Lionel Bernard , Sylvain Coq , Marco Moretti , Sandra Lavorel , Christiane Gallet
Publication : Functional Ecology
Date : 2025
Volume : 27
Issue : 4
Pages : 1064-1074
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Despite their potential to provide a mechanistic understanding of ecosystem processes, the functional traits that govern interaction networks remain poorly understood. We investigated the extent to which biomechanical traits are related to consumption in a plant–grasshopper herbivory network. Using a choice experiment, we assessed the feeding patterns of 26 grasshopper species for 24 common plant species from subalpine grasslands. We quantified shear and punch toughness for each plant species, while grasshopper incisive and molar strengths were estimated by a lever mechanics model, following the measurement of mandibular traits. Models incorporating co-phylogenetic effects showed that the ratio between the grasshopper incisive strength and plant toughness, that reflects the cutting effort, is correlated with the mass of plant eaten. Moreover, a strong relationship between the incisive strength of the grasshoppers and the weighed mean toughness of the plants they eat was found. Our results suggest that biomechanical constraints imposed by plants influence the evolution of grasshoppers' mandibular traits. Such scaling relationships offer promising avenues towards the understanding of trait – function links in interaction networks.
Auteurs, date et publication :
Auteurs Sébastien Ibanez , Sandra Lavorel , Sara Puijalon , Marco Moretti
Publication : Functional Ecology
Date : 2025
Volume : 27
Issue : 2
Pages : 479-489
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Alpine habitats are one of the most vulnerable ecosystems to environmental change, however, little information is known about the drivers of plant–fungal interactions in these ecosystems and their resilience to climate change. We investigated the influence of the main drivers of ectomycorrhizal (EM) fungal communities along elevation and environmental gradients in the alpine zone of the European Alps and measured their degree of specialisation using network analysis. We sampled ectomycorrhizas of Dryas octopetala, Bistorta vivipara and Salix herbacea, and soil fungal communities at 28 locations across five countries, from the treeline to the nival zone. We found that: (1) EM fungal community composition, but not richness, changes along elevation, (2) there is no strong evidence of host specialisation, however, EM fungal networks in the alpine zone and within these, EM fungi associated with snowbed communities, are more specialised than in other alpine habitats, (3) plant host population structure does not influence EM fungal communities, and (4) most variability in EM fungal communities is explained by fine-scale changes in edaphic properties, like soil pH and total nitrogen. The higher specialisation and narrower ecological niches of these plant–fungal interactions in snowbed habitats make these habitats particularly vulnerable to environmental change in alpine ecosystems.
Auteurs, date et publication :
Auteurs Ricardo Arraiano-Castilho , Martin I. Bidartondo , Tuula Niskanen , James J. Clarkson , Ivano Brunner , Stephan Zimmermann , Beatrice Senn-Irlet , Beat Frey , Ursula Peintner , Tanja Mrak , Laura M. Suz
Publication : New Phytologist
Date : 2025
Volume : 229
Issue : 5
Pages : 2901-2916
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs P. Choler
Publication : Biogeosciences
Date : 2015
Volume : 12
Issue : 12
Pages : 3885-3897
Catégorie(s)
#CNRS #Lautaret #UGARésumé
The Convention on Biological Diversity (CBD) aims at the conservation of all three levels of biodiversity, that is, ecosystems, species and genes. Genetic diversity represents evolutionary potential and is important for ecosystem functioning. Unfortunately, genetic diversity in natural populations is hardly considered in conservation strategies because it is difficult to measure and has been hypothesised to co-vary with species richness. This means that species richness is taken as a surrogate of genetic diversity in conservation planning, though their relationship has not been properly evaluated. We tested whether the genetic and species levels of biodiversity co-vary, using a large-scale and multi-species approach. We chose the high-mountain flora of the Alps and the Carpathians as study systems and demonstrate that species richness and genetic diversity are not correlated. Species richness thus cannot act as a surrogate for genetic diversity. Our results have important consequences for implementing the CBD when designing conservation strategies.
Auteurs, date et publication :
Auteurs Pierre Taberlet , Niklaus E. Zimmermann , Thorsten Englisch , Andreas Tribsch , Rolf Holderegger , Nadir Alvarez , Harald Niklfeld , Gheorghe Coldea , Zbigniew Mirek , Atte Moilanen , Wolfgang Ahlmer , Paolo Ajmone Marsan , Enzo Bona , Maurizio Bovio , Philippe Choler , Elżbieta Cieślak , Licia Colli , Vasile Cristea , Jean-Pierre Dalmas , Božo Frajman
Publication : Ecology Letters
Date : 2025
Volume : 15
Issue : 12
Pages : 1439-1448