Résumé
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)
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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)
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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
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Functional trait differences among species are increasingly used to infer the effects of biotic and abiotic processes on species coexistence. Commonly, the trait diversity observed within communities is compared to patterns simulated in randomly generated communities based on sampling within a region. The resulting patterns of trait convergence and divergence are assumed to reveal abiotic and biotic processes, respectively. However, biotic processes such as competition can produce both trait divergence and convergence, through either excluding similar species (niche differences, divergence) or excluding dissimilar species (weaker competitor exclusion, convergence). Hence, separating biotic and abiotic processes that can produce identical patterns of trait diversity, or even patterns that neutralize each other, is not feasible with previous methods. We propose an operational framework in which the functional trait dissimilarity within communities (FDcomm) is compared to the corresponding trait dissimilarity expected from the species pool (i.e., functional species pool diversity, FDpool). FDpool includes the set of potential species for a site delimited by the operating environmental and dispersal limitation filters. By applying these filters, the resulting pattern of trait diversity is consistent with biotic processes, i.e., trait divergence (FDcomm . FDpool) indicates niche differentiation, while trait convergence (FDcomm , FDpool) indicates weaker competitor exclusion. To illustrate this framework, with its potential application and constraints, we analyzed both simulated and field data. The functional species pool framework more consistently detected the simulated trait diversity patterns than previous approaches. In the field, using data from plant communities of typical Northern European habitats in Estonia, we found that both niche-based and weaker competitor exclusion influenced community assembly, depending on the traits and community considered. In both simulated and field data, we demonstrated that only by estimating the species pool of a site is it possible to differentiate the patterns of trait dissimilarity produced by operating biotic processes. The framework, which can be applied with both functional and phylogenetic diversity, enables a reinterpretation of community assembly processes. Solving the challenge of defining an appropriate reference species pool for a site can provide a better understanding of community assembly.
Auteurs, date et publication :
Auteurs Francesco de Bello , Jodi N. Price , Tamara Münkemüller , Jaan Liira , Martin Zobel , Wilfried Thuiller , Pille Gerhold , Lars Götzenberger , Sébastien Lavergne , Jan Lepš , Kristjan Zobel , Meelis Pärtel
Publication : Ecology
Date : 2025
Volume : 93
Issue : 10
Pages : 2263-2273
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Evergreen plants growing at high latitudes or high elevations may experience freezing events in their photosynthetic tissues. Freezing events can have physical and physiological effects on the leaves which alter leaf optical properties affecting remote and proximal sensing parameters. We froze leaves of six alpine plant species (Soldanella alpina, Ranunculus kuepferi, Luzula nutans, Gentiana acaulis, Geum montanum, and Centaurea uniflora) and three evergreen forest understorey species (Hepatica nobilis, Fragaria vesca and Oxalis acetosella), and assessed their spectral transmittance and optically measured pigments, as well as photochemical efficiency of photosystem II (PSII) as an indicator of freezing damage. Upon freezing, leaves of all the species transmitted more photosynthetically active radiation (PAR) and some species had increased ultraviolet-A (UV-A) transmittance. These differences were less pronounced in alpine than in understorey species, which may be related to higher chlorophyll degradation, visible as reduced leaf chlorophyll content upon freezing in the latter species. Among these understorey forbs, the thin leaves of O. acetosella displayed the largest reduction in chlorophyll (−79%). This study provides insights into how freezing changes the leaf optical properties of wild plants which could be used to set a baseline for upscaling optical reflectance data from remote sensing. Changes in leaf transmittance may also serve to indicate photosynthetic sufficiency and physiological tolerance of freezing events, but experimental research is required to establish this functional association.
Auteurs, date et publication :
Auteurs Twinkle Solanki , José Ignacio García Plazaola , T. Matthew Robson , Beatriz Fernández Marín
Publication : Photochemical & Photobiological Sciences
Date : 2022
Issue : 21
Pages : 997-1009
Catégorie(s)
#CNRS #Lautaret #UGARésumé
The significance of foliar uptake of nitrogen (N) compounds in natural conditions is not well understood, despite growing evidence of its importance to plant nutrition. In subalpine meadows, N-limitation fosters the dominance of specific subalpine plant species, which in turn ensure the provision of essential ecosystems services. Understanding how these plants absorb N and from which sources is important to predict ecological consequences of increasing N deposition. Here, we investigate the sources of N to plants from subalpine meadows with distinct land-use history in the French Alps, using the triple isotopes (Δ17 O, δ18 O, and δ15 N) of plant tissue nitrate (NO3- ). We use this approach to evaluate the significance of foliar uptake of atmospheric NO3- (NO3-atm ). The foliar uptake of NO3-atm accounted for 4-16% of the leaf NO3- content, and contributed more to the leaf NO3- pool after peak biomass. Additionally, the gradual 15 N enrichment of NO3- from the soil to the leaves reflected the contribution of NO3-atm assimilation to plants' metabolism. The present study confirms that foliar uptake is a potentially important pathway for NO3-atm into subalpine plants. This is of major significance as N emissions (and deposition) are predicted to increase globally in the future. This article is protected by copyright. All rights reserved.
Auteurs, date et publication :
Auteurs Ilann Bourgeois , Jean-Christophe Clément , Nicolas Caillon , Joël Savarino
Publication : New Phytologist
Date : 2019
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Land use has an effect on seed strategies. It is debated, however, whether disturbances such as mowing select for one dominant regeneration strategy (e.g. ruderals) or allows for more species with diverse recruitment strategies to establish. We tested if there is a filtering of seed traits in subalpine grasslands and what is the effect of mowing on community mean seed traits and their diversity. We measured seed mass and seed number of most species from subalpine grasslands in the French Alps, in an experiment consisting of short- and long-term mowing. We calculated for each treatment average seed mass and number as well as functional divergence. Mowing had no effect either on mean seed trait values or trait diversity, but rather reversed the effect of moisture on seed traits. Most importantly, besides soil moisture, communities followed a continuum from grasslands dominated by species with heavy seeds to grasslands with high divergence in seed mass. These results suggest the existence of an axis of functional divergence–convergence for seed mass in response to factors other than disturbance, though we were not able to identify which. Functional space (i.e. available niches along seed trait dimensions) exists for species with varied strategies in some of the communities, as opposed to others where species with heavy seed masses prevail. Reproductive strategies and the availability of diverse regeneration niches may determine a more important assembly rule of plant species in subalpine communities than previously considered.
Auteurs, date et publication :
Auteurs Flore Viard-Crétat , Francesco de Bello , Ove Eriksson , Marie-Pascale Colace , Sandra Lavorel
Publication : Basic and Applied Ecology
Date : 2025
Volume : 12
Issue : 5
Pages : 423-431
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs Ceres Barros , Maya Guéguen , Rolland Douzet , Marta Carboni , Isabelle Boulangeat , Niklaus E. Zimmermann , Tamara Münkemüller , Wilfried Thuiller , Akira Mori
Publication : Journal of Applied Ecology
Date : 2025
Volume : 54
Issue : 1
Pages : 39-50