Résumé
Reductions in community evenness can lead to local extinctions as dominant species exclude subordinate species; however, herbivores can prevent competitive exclusion by consuming otherwise dominant plant species, thus increasing evenness. While these predictions logically result from chronic, gradual reductions in evenness, rapid, temporary pulses of dominance may also reduce species richness. Short pulses of dominance can occur as biotic or abiotic conditions temporarily favour one or a few species, manifested as increased temporal variability (the inverse of temporal stability) in community evenness. Here, we tested whether consumers help maintain plant diversity by reducing the temporal variability in community evenness. We tested our hypothesis by reducing herbivore abundance in a detailed study of a developing, tallgrass prairie restoration. To assess the broader implications of the importance of herbivory on community evenness as well as potential mechanisms, we paired this study with a global herbivore reduction experiment. We found that herbivores maintained plant richness in a tallgrass prairie restoration by limiting temporary pulses in dominance by a single species. Dominance by an annual species in a single year was negatively associated with species richness, suggesting that short pulses of dominance may be sufficient to exclude subordinate species. The generality of this site-level relationship was supported by the global experiment in which inter-annual variability in evenness declined in the presence of vertebrate herbivores over timeframes ranging in length from 2 to 5 years, preventing declines in species richness. Furthermore, inter-annual variability of community evenness was also negatively associated with pre-treatment species richness. Synthesis. A loss or reduction of herbivores can destabilize plant communities by allowing brief periods of dominance by one or a few species, potentially triggering a feedback cycle of dominance and extinction. Such cycles may not occur immediately following the loss of herbivores, being delayed until conditions allow temporary periods of dominance by a subset of plant species.
Auteurs, date et publication :
Auteurs Brent Mortensen , Brent Danielson , W. Stanley Harpole , Juan Alberti , Carlos Alberto Arnillas , Lori Biederman , Elizabeth T. Borer , Marc W. Cadotte , John M. Dwyer , Nicole Hagenah , Yann Hautier , Pablo Luis Peri , Eric W. Seabloom
Publication : Journal of Ecology
Date : 2025
Volume : 106
Issue : 1
Pages : 101-112
Catégorie(s)
#CEREEP #CNRS #ENSRésumé
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 #UGAAuteurs, date et publication :
Auteurs Holger Teichert , Stefan Dötterl , Gerhard Gottsberger
Publication : Plant Systematics and Evolution
Date : 2025
Volume : 291
Issue : 1-2
Pages : 25-33
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Gerardo L Robledo , Ernesto M Giorgio , Clovis RP Franco , Orlando Popoff , Cony Decock
Publication : Check List
Date : 2025
Volume : 10
Issue : 6
Pages : 1514-1519
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Ludovic Henneron , Corinne Sarthou , Jean‐Christophe de Massary , Jean‐François Ponge
Publication : Ecography
Date : 2025
Volume : 42
Issue : 9
Pages : 1536-1547
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Elvire Bestion , Julien Cote , Staffan Jacob , Laurane Winandy , Delphine Legrand
Publication : Current Opinion in Insect Science
Date : 2025
Volume : 35
Pages : 117-122
Catégorie(s)
#CNRS #Metatron terrestreRésumé
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 #UGARésumé
This paper reviews the currently available optical sensors, their limitations and opportunities for deployment at Eddy Covariance (EC) sites in Europe. This review is based on the results obtained from an online survey designed and disseminated by the Co-cooperation in Science and Technology (COST) Action ESO903—“Spectral Sampling Tools for Vegetation Biophysical Parameters and Flux Measurements in Europe” that provided a complete view on spectral sampling activities carried out within the different research teams in European countries. The results have highlighted that a wide variety of optical sensors are in use at flux sites across Europe, and responses further demonstrated that users were not always fully aware of the key issues underpinning repeatability and the reproducibility of their spectral measurements. The key findings of this survey point towards the need for greater awareness of the need for standardisation and development of a common protocol of optical sampling at the European EC sites.
Auteurs, date et publication :
Auteurs Manuela Balzarolo , Karen Anderson , Caroline Nichol , Micol Rossini , Loris Vescovo , Nicola Arriga , Georg Wohlfahrt , Jean-Christophe Calvet , Arnaud Carrara , Sofia Cerasoli , Sergio Cogliati , Fabrice Daumard , Lars Eklundh , Jan A. Elbers , Fatih Evrendilek , Rebecca N. Handcock , Jörg Kaduk , Katja Klumpp , Bernard Longdoz , Giorgio Matteucci
Publication : Sensors
Date : 2011
Volume : 11
Issue : 8
Pages : 7954-7981
Catégorie(s)
#CNRS #FORET PuechabonRésumé
Understanding whether tree growth is limited by carbon gain (source limitation) or by the direct effect of environmental factors such as water deficit or temperature (sink limitation) is crucial for improving projections of the effects of climate change on forest productivity.
Auteurs, date et publication :
Auteurs Morine Lempereur , Nicolas K Martin-StPaul , Claire Damesin , Richard Joffre , Jean-Marc Ourcival , Alain Rocheteau , Serge Rambal
Publication : New Phytologist
Date : 2025
Pages : 12