Résumé
Important biochemical reactions in soils are catalyzed by extracellular enzymes, which are synthesized by microbes and plant roots. Although enzyme activities can significantly affect the decomposition of soil organic matter and thus influence the storage and cycling of carbon (C) and nitrogen (N), it is not clear how enzyme activities relate to changes in the C and N content of different grassland soils. Here we address whether the activity of C-acquiring (b-1,4-glucosidase, BG) and N-acquiring (L-leucine aminopeptidase (LAP) and b-1,4-N-acetyl-glucosaminidase (NAG)) enzymes is linked to changes in the C and N content of a variety of human-managed grassland soils. We selected soils which have a well-documented management history going back at least 19 years in relation to changes in land use (grazing, mowing, ploughing), nutrient fertilization and lime (CaCO3) applications. Overall we found a positive relationship between BG activity and soil C content as well as between LAP þ NAG activity and soil N. These positive relationships occurred across grasslands with very different soil pH and management history but not in intensively managed grasslands where increases in soil bulk density (i.e. high soil compaction) negatively affected enzyme activity. We also found evidence that chronic nutrient fertilization contributed to increases in soil C content and this was associated with a significant increase in BG activity when compared to unfertilized soils. Our study suggests that while the activities of C- and N-acquiring soil enzymes are positively related to soil C and N content, these activities respond significantly to changes in management (i.e. soil compaction and nutrient fertilization). In particular, the link between BG activity and the C content of long-term fertilized soils deserves further investigation if we wish to improve our understanding of the C sequestration potential of human-managed grassland soils.
Auteurs, date et publication :
Auteurs Valeria L. Cenini , Dario A. Fornara , Geoffrey McMullan , Nigel Ternan , Rachael Carolan , Michael J. Crawley , Jean-Christophe Clément , Sandra Lavorel
Publication : Soil Biology and Biochemistry
Date : 2025
Volume : 96
Pages : 198-206
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Abstract
Asteraceae, the daisy family, are one of the most diverse families of angiosperms and are predominant in many ecosystems, including grasslands, deserts, savannas and high-elevation mountains. They are characterized by a peculiar inflorescence, the capitulum, which mimics a flower, but is actually made up of many tightly grouped florets. The capitulum is considered a key character underpinning the impressive evolutionary success of the family, and it plays a pivotal role in the economic importance of the family, given that many species are cultivated for their capitulum for agricultural and horticultural purposes. However, to date, there is still no comprehensive understanding of the extent of the morphological diversity of capitula across lineages of Asteraceae. This is mainly due to a lack of appropriate tools for describing such a complex and condensed structure. To address the problem, we present a protocol for characterizing the full diversity of capitula from any lineage of Asteraceae. This involves making a whole dissection of a capitulum from fresh material; it is simple and cost-effective and requires relatively easy-to-transport equipment meaning that it can be done during fieldwork.
Auteurs, date et publication :
Auteurs Lin Fu , Luis Palazzesi , Jaume Pellicer , Manica Balant , Maarten J M Christenhusz , Luca Pegoraro , Iván Pérez-Lorenzo , Ilia J Leitch , Oriane Hidalgo
Publication : Botanical Journal of the Linnean Society
Date : 2023
Volume : 201
Issue : 4
Pages : 391-399
Catégorie(s)
#CNRS #Lautaret #UGARésumé
The lichen collection of the alpine station of Lautaret developed by Georges Clauzade and Yves Rondon is a testimony to the early lichenological researches conducted in the region. Rich of 450 samples, with about 300 species, it includes nearly 60 of rare to very rare species which some have been observed for the first time in the area of the Lautaret.
Auteurs, date et publication :
Auteurs Juliette Asta , Christophe Perrier , Natacha Clairet
Publication : Bulletin de la Société Linnéenne de Lyon
Date : 2025
Volume : 88
Pages : 48
Catégorie(s)
#CNRS #Lautaret #UGARésumé
High-throughput sequencing of amplicons from environmental DNA samples permits rapid, standardized and comprehensive biodiversity assessments. However, retrieving and interpreting the structure of such data sets requires efficient methods for dimensionality reduction. Latent Dirichlet Allocation (LDA) can be used to decompose environmental DNA samples into overlapping assemblages of co-occurring taxa. It is a flexible model-based method adapted to uneven sample sizes and to large and sparse data sets. Here, we compare LDA performance on abundance and occurrence data, and we quantify the robustness of the LDA decomposition by measuring its stability with respect to the algorithm's initialization. We then apply LDA to a survey of 1,131 soil DNA samples that were collected in a 12-ha plot of primary tropical forest and amplified using standard primers for bacteria, protists, fungi and metazoans. The analysis reveals that bacteria, protists and fungi exhibit a strong spatial structure, which matches the topographical features of the plot, while metazoans do not, confirming that microbial diversity is primarily controlled by environmental variation at the studied scale. We conclude that LDA is a sensitive, robust and computationally efficient method to detect and interpret the structure of large DNA-based biodiversity data sets. We finally discuss the possible future applications of this approach for the study of biodiversity.
Auteurs, date et publication :
Auteurs Guilhem Sommeria‐Klein , Lucie Zinger , Eric Coissac , Amaia Iribar , Heidy Schimann , Pierre Taberlet , Jérôme Chave
Publication : Molecular Ecology Resources
Date : 2025
Volume : 20
Issue : 2
Pages : 371-386
Catégorie(s)
#ANR-Citation #CNRS #FORET Nouragues #UGARésumé
In the current biodiversity crisis, one of the crucial questions is how quickly plant communities can acclimate to climate warming and longer growing seasons to buffer the impairment of community functioning. Answering this question is pivotal especially for mountain grasslands that experience harsh conditions but provide essential ecosystem services to people. We conducted a reciprocal transplant experiment along an elevation gradient (1,920 m vs. 2,450 m) in the French Alps to test the ability of plant species and communities to acclimate to warming and cooling. For 3 years, we measured weekly the timing of phenological events (e.g. start of flowering or greening) and the length of phenological stages linked to demographic performance (e.g. lengths of flowering or greening periods). We found that warming (and cooling) changed the timing of phenological events strongly enough to result in complete acclimation for graminoids, for communities in early and mid-season, but not at all for forbs. For example, warming resulted in later greening of communities and delayed all phenophases of graminoids. Lengths of phenological stages did not respond strongly enough to climate change to acclimate completely, except for graminoids. For example, warming led to an acclimation lag in the community's yearly productivity and had a strong negative impact on flowering of forbs. Overall, when there was an acclimation failure, responses to cooling were mostly symmetric and confirmed slow acclimation in mountain grasslands. Synthesis. Our study highlights that phenological plasticity cannot prevent disruption of community functioning under climate warming in the short term. The failures to acclimate after 3 years of warming signals that species and communities underperform and are probably at high risk of being replaced by locally better-adapted plants.
Auteurs, date et publication :
Auteurs Billur Bektaş , Wilfried Thuiller , Amelie Saillard , Philippe Choler , Julien Renaud , Marie-Pascale Colace , Raphael Della Vedova , Tamara Münkemüller
Publication : Journal of Ecology
Date : 2025
Volume : 109
Issue : 9
Pages : 3396-3410
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Remote sensing is an invaluable tool for tracking decadal-scale changes in vegetation greenness in response to climate and land use changes. While the Landsat archive has been widely used to explore these trends and their spatial and temporal complexity, its inconsistent sampling frequency over time and space raises concerns about its ability to provide reliable estimates of annual vegetation indices such as the annual maximum normalised difference vegetation index (NDVI), commonly used as a proxy of plant productivity. Here we demonstrate for seasonally snow-covered ecosystems, that greening trends derived from annual maximum NDVI can be significantly overestimated because the number of available Landsat observations increases over time, and mostly that the magnitude of the overestimation varies along environmental gradients. Typically, areas with a short growing season and few available observations experience the largest bias in greening trend estimation. We show these conditions are met in late snowmelting habitats in the European Alps, which are known to be particularly sensitive to temperature increases and present conservation challenges. In this critical context, almost 50% of the magnitude of estimated greening can be explained by this bias. Our study calls for greater caution when comparing greening trends magnitudes between habitats with different snow conditions and observations. At a minimum we recommend reporting information on the temporal sampling of the observations, including the number of observations per year, when long-term studies with Landsat observations are undertaken.
Auteurs, date et publication :
Auteurs Arthur Bayle , Simon Gascoin , Logan T. Berner , Philippe Choler
Publication : Ecography
Date : 2025
Volume : 2024
Issue : 12
Pages : e07394
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Up to now, the most widely accepted idea of the periglacial environment is that of treeless ecosystems such as the arctic or the alpine tundra, also called the tabula rasa paradigm. However, several palaeoecological studies have recently challenged this idea, that is, treeless environments in periglacial areas where all organisms would have been exterminated near the glacier formed during the Last Glacial Maximum, notably in the Scandinavian mountains. In the Alps, the issue of glacial refugia of trees remains unanswered. Advances in glacier reconstructions show that ice domes did not cover all upper massifs, but glaciers filled valleys. Here, we used fossils of plant and malacofauna from a travertine formation located in a high mountain region to demonstrate that trees (Pinus, Betula) grew with grasses during the Lateglacial-Holocene transition, while the glacier fronts were 200–300 m lower. The geothermal travertine started to accumulate more than 14,500 years ago, but became progressively more meteogene about 11,500 years ago due to a change in groundwater circulation. With trees, land snails (gastropods) associated to woody or open habitats and aquatic mollusc were also present at the onset of the current interglacial, namely the Holocene. The geothermal spring, due to warm water and soil, probably favoured woody glacial ecosystems. This new finding of early tree growth, combined with other scattered proofs of the tree presence before 11,000 years ago in the western Alps, changes our view of the tree distribution in periglacial environments, supporting the notion of tree refugia on nunataks in an ocean of glaciers. Therefore, the tabula rasa paradigm must be revisited because it has important consequences on the global changes, including postglacial plant migrations and biogeochemical cycles.
Auteurs, date et publication :
Auteurs Christopher Carcaillet , Jean-Louis Latil , Sébastien Abou , Adam Ali , Bassam Ghaleb , Frédéric Magnin , Paul Roiron , Serge Aubert
Publication : Global Change Biology
Date : 2025
Volume : 24
Issue : 6
Pages : 2476-2487
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Local adaptation and phenotypic plasticity are two important characteristics of alpine plants to overcome the threats caused by global changes. Among alpine species, Arabis alpina is characterised by an unusually wide altitudinal amplitude, ranging from 800 to 3,100 m of elevation in the French Alps. Two non-exclusive hypotheses can explain the presence of A. alpina across this broad ecological gradient: adaptive phenotypic plasticity or local adaptation, making this species especially useful to better understand these phenomena in alpine plant species. We carried out common garden experiments at two different elevations with maternal progenies from six sites that differed in altitude. We showed that (1) key phenotypic traits (morphotype, total fruit length, growth, height) display significant signs of local adaptation, (2) most traits studied are characterised by a high phenotypic plasticity between the two experimental gardens and (3) the two populations from the highest elevations lacked morphological plasticity compared to the other populations. By combining two genome scan approaches (detection of selection and association methods), we isolated a candidate gene (Sucrose-Phosphate Synthase 1). This gene was associated with height and local average temperature in our studied populations, consistent with previous studies on this gene in Arabidopsis thaliana. Synthesis. Given the nature of the traits involved in the detected pattern of local adaptation and the relative lack of plasticity of the two most extreme populations, our findings are consistent with a scenario of a locally adaptive stress response syndrome in high elevation populations. Due to a reduced phenotypic plasticity, an overall low intra-population genetic diversity of the adaptive traits and weak gene flow, populations of high altitude might have difficulties to cope with, e.g. a rise of temperature.
Auteurs, date et publication :
Auteurs Pierre de Villemereuil , Médéric Mouterde , Oscar E. Gaggiotti , Irène Till‐Bottraud
Publication : Journal of Ecology
Date : 2025
Volume : 106
Issue : 5
Pages : 1952-1971
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs Peter Streb , Gabriel Cornic , Cornelius Lütz
Date : 2025
Pages : 75-97
Catégorie(s)
#CNRS #Lautaret #UGARésumé
In subalpine grasslands of the central French Alps, cessation of traditional mowing promotes dominance of Patzkea paniculata (L.) G.H.Loos (Poaceae) tussocks, with high biomass but low fodder quality. Mowing limits P. paniculata abundance through the depletion of its water-soluble carbohydrate (WSC) reserves, which sustain early spring growth initiation. However, the effectiveness of mowing effects is modulated by grassland functional composition, fertilization and climate change, as WSC compounds, and notably fructans, support plant physiological responses to climate stresses such as drought or frost.
Auteurs, date et publication :
Auteurs L. Bernard , M.‐L. Decau , A. Morvan‐Bertrand , S. Lavorel , J.‐C. Clément , F. Loreto
Publication : Plant Biology
Date : 2020
Pages : plb.13081