Auteurs, date et publication :
Auteurs Johanne Lebrun Thauront , Severin Luca Bellè , Marcus Schiedung , Amicie Delahaie , Marija Stojanova , François Baudin , Pierre Barré , Samuel Abiven
Date : 2024
Catégorie(s)
#CNRS #Ecotron IleDeFrance #ENSRésumé
Synthetic Aperture Radar (SAR) texture has been demonstrated to have the potential to improve forest biomass estimation using backscatter. However, forests are 3D objects with a vertical structure. The strong penetration of SAR signals means that each pixel contains the contributions of all the scatterers inside the forest canopy, especially for the P-band. Consequently, the traditional texture derived from SAR images is affected by forest vertical heterogeneity, although the influence on texture-based biomass estimation has not yet been explicitly explored. To separate and explore the influence of forest vertical heterogeneity, we introduced the SAR tomography technique into the traditional texture analysis, aiming to explore whether TomoSAR could improve the performance of texture-based aboveground biomass (AGB) estimation and whether texture plus tomographic backscatter could further improve the TomoSAR-based AGB estimation. Based on the P-band TomoSAR dataset from TropiSAR 2009 at two different sites, the results show that ground backscatter variance dominated the texture features of the original SAR image and reduced the biomass estimation accuracy. The texture from upper vegetation layers presented a stronger correlation with forest biomass. Texture successfully improved tomographic backscatter-based biomass estimation, and the texture from upper vegetation layers made AGB models much more transferable between different sites. In addition, the correlation between texture indices varied greatly among different tomographic heights. The texture from the 10 to 30 m layers was able to provide more independent information than the other layers and the original images, which helped to improve the backscatter-based AGB estimation.
Auteurs, date et publication :
Auteurs Zhanmang Liao , Binbin He , Xingwen Quan
Publication : International Journal of Applied Earth Observation and Geoinformation
Date : 2020
Volume : 88
Pages : 102049
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
The ongoing decline in biodiversity has fuelled concerns about its impact on ecosystem functioning. Mediterranean oak forests may prove very sensitive to global change, which could strongly influence the species composition of plant communities and thereby affect ecosystem processes. To determine the potential outcome of shifts in species composition on litter decomposition dynamics, we conducted a full-factorial decomposition experiment over a gradient of litter species diversity in a Mediterranean Downy oak (Quercus pubescens Willd.) forest. We used litter from the three dominant tree species naturally present in the Downy oak forest and litter from Aleppo pine (Pinus halepensis Mill.) in anticipation of its possible spread in the future with global change. Litter water holding capacity and N/P ratio were the most important and positive drivers of decomposition process. In contrast to other ecosystems where synergistic non-additive effects are prevalent, we observed 54% of additive and 46% of non-additive effects on litter mass loss in our Mediterranean ecosystem. These results could indicate less complementarity among decomposers for decomposition of diverse plant material in such a stressful climate. Moreover, dominant tree species are of key importance for nutrient availability, and the arrival of Aleppo pine would strongly reduce the N release during the decomposition process. Based on calculations of an annual partial nutrient budget at the ecosystem level, we showed that a shift in plant communities could affect nutrient release, ranging from 5 to 36% for N and 63 to 83% for P depending on the co-occurring tree species in the Downy oak forest.
Auteurs, date et publication :
Auteurs Mathieu Santonja , Virginie Baldy , Catherine Fernandez , Jérôme Balesdent , Thierry Gauquelin
Publication : Ecosystems
Date : 2015
Volume : 18
Issue : 7
Pages : 1253-1268
Catégorie(s)
#CNRS #FORET O3HPAuteurs, date et publication :
Auteurs Elodie Merlier , Gabriel Hmimina , Matthieu Bagard , Eric Dufrêne , Kamel Soudani
Publication : Photochemical & Photobiological Sciences
Date : 2025
Volume : 16
Issue : 8
Pages : 1238-1251
Catégorie(s)
#ANR-Citation #CNRS #Ecotron IleDeFrance #ENSRésumé
Climate change will increase the level of drought stress experienced by plant communities, but the spatial distribution of projected changes in dryness remains highly uncertain. Species can, to some extent, deal with climate uncertainty through natural variation in adaptive responses to environmental heterogeneity and predictability. Biodiversity conservation could thus target populations pre-adapted to climatic heterogeneity to anticipate climate uncertainty. Disentangling adaptive evolution of trait means versus trait plasticity, however, requires a sampling design with genetic replicates grown under distinct environmental conditions. Here, we applied three soil moisture treatments to genetic replicates of Fragaria vesca plants raised from seeds that were sampled in distinct topographical settings, to study adaptive trait and plasticity divergence in response to drought. We demonstrate that various plant traits evolved along distinct topographical gradients. Populations on south-exposed slopes, for example, retained high levels of both flowering and runner formation under drought stress, while north-faced populations hardly flowered under reduced soil moisture levels. Aspect but not elevation was found to coincide with variation in plant traits, suggesting that microenvironmental variation rather than general clines in elevation drive evolution in mountainous landscapes. Our results also indicate that traits and their plasticity can evolve independently in response to distinct topographical stressors. Synthesis. We conclude that heterogeneous landscapes (a) harbour micro-refugia of adaptive genetic diversity that protect natural populations against environmental change, and (b) represent invaluable sources of quantitative genetic variation that could support conservation where climate projections are inconclusive.
Auteurs, date et publication :
Auteurs Hanne De Kort , Bart Panis , Kenny Helsen , Rolland Douzet , Steven B. Janssens , Olivier Honnay
Publication : Journal of Ecology
Date : 2025
Volume : 108
Issue : 4
Pages : 1465-1474
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs Sarah Chaloupka , Camilo Rodríguez
Publication : Herpetology Notes
Date : 2025
Volume : 14
Pages : 209-213
Catégorie(s)
#⛔ No DOI found #CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs B. Urbani , D. Youlatos , M. M. Kowalewski
Publication : Primate Biology
Date : 2025
Volume : 7
Issue : 2
Pages : 25–33
Catégorie(s)
#CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Elodie A Courtois , Kevin Pineau , Benoit Villette , Dirk S Schmeller , Philippe Gaucher
Publication : Phyllomedusa
Date : 2025
Volume : 11
Pages : 63-70
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Tropical rainforests host exceptional biodiversity and provide important ecosystem services, but they are facing anthropogenic and climatic threats. Preserving the genetic diversity of forest tree populations is essential for their capacity to adapt and exhibit resilience to environmental changes and anthropogenic pressures. Here, we collected conservation genetic baseline information for the heavily exploited timber tree Dicorynia guianensis Amshoff (Fabaceae) at the regional and local levels in French Guiana. Based on genotyping at five microsatellite loci in 1566 individuals collected in 23 forest locations, we documented the genetic differentiation of locations from the West of French Guiana and identified distinctive genetic diversity patterns with higher genetic diversity and some bottlenecked sites in the East and inland. The regional population genetic structure is likely the result of past population isolation in distinct Pleistocene refuges and different demographic histories potentially influenced by Holocene drought periods or palaeofires. Assessment of spatial genetic structure (Sp from 0 to 0.028) in five intensively sampled locations yielded estimates of Wright’s neighborhood size of 35 to 313, indicative of restricted dispersal and local metapopulation dynamics, and useful as baseline information to assess the effects of selective logging for conservation management. These results support the current management strategies with low impact extraction of D. guianensis in three zones of the French Guiana permanent forest domain and allow us to make recommendations for further research and management to best preserve its genetic diversity and adaptive potential.
Auteurs, date et publication :
Auteurs Julien Bonnier , Niklas Tysklind , Valérie Troispoux , Ivan Scotti , Stéphanie Barthe , Olivier Brunaux , Stéphane Guitet , Stéphane Traissac , Myriam Heuertz
Publication : Tree Genetics & Genomes
Date : 2025
Volume : 20
Issue : 1
Pages : 2
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
* Sex-biased dispersal, that is, the difference in dispersal between males and females, is thought to be the consequence of any divergent evolutionary responses between sexes. In anisogamous species, asymmetry in parental investment may lead to sexual conflict, which entails male–male competition (for sexual partner access), female–female competition (for feeding or egg-laying habitat patches) and/or male–female competition (antagonistic co-evolution). * As competition is one of the main causes of dispersal evolution, intra- and intersexual competition should have strong consequences on sex-biased dispersal. However, very few experimental studies, if any, have simultaneously addressed the effect of biased sex ratio on (i) each dispersal stage (emigration, transience, immigration), (ii) the dispersal phenotype and (iii) the colonization success of new habitat in order to fully separate the effects of varying male and female density. * Here, we used the Metatron, a unique experimental system composed of 48 interconnected enclosed patches dedicated to the study of dispersal in meta-ecosystems, to investigate the effect of sex ratio on dispersal in a butterfly. We created six populations with three different sex ratios in pairs of patches and recorded individual movements in these simple metapopulations. * Emigration was higher when the proportion of males was higher, and individuals reached the empty patch at a higher rate when the sex ratio in the departure patch was balanced. Males had a better dispersal success than females, which had a lower survival rate during dispersal and after colonization. We also showed that sex and wing size are major components of the dispersal response. * We did not observe sex-biased dispersal; our results thus suggest that female harassment by males and male–male competition might be more important mechanisms for the dispersal of females and males, than the search for a mating partner. Furthermore, the demonstration of a differential mortality between males and females during dispersal provides causal hypotheses of the evolution of sex-biased dispersal.
Auteurs, date et publication :
Auteurs Audrey Trochet , Delphine Legrand , Nicolas Larranaga , Simon Ducatez , Olivier Calvez , Julien Cote , Jean Clobert , Michel Baguette
Publication : Journal of Animal Ecology
Date : 2025
Volume : 82
Issue : 5
Pages : 946-955