Auteurs, date et publication :
Auteurs Jesus Rodrıguez-Calcerrada , Carsten Jaeger , Jean M Limousin , Jean M Ourcival , Richard Joffre , Serge Rambal
Publication : Functional Ecology
Date : 2025
Pages : 13
Catégorie(s)
#CNRS #FORET PuechabonAuteurs, date et publication :
Auteurs Isabelle Maréchaux , Laurent Saint‐André , Megan K Bartlett , Lawren Sack , Jerome Chave
Publication : Journal of Ecology
Date : 2025
Catégorie(s)
#ANR-Citation #CNRS #FORET NouraguesRésumé
In the Mediterranean region, a reduction of annual precipitation and a longer and drier summer season are expected with climate change by the end of the century, eventually endangering forest survival. To cope with such rapid changes, trees may modulate their morpho-anatomical and physiological traits. In the present study, we focused on the variation in leaf gas exchange and different leaf morpho-anatomical functional traits of Quercus pubescens Willd. in summer using a long-term drought experiment in natura consisting of a dynamic rainfall exclusion system where trees have been submitted to amplified drought (AD) (similar to-30% of annual precipitation) since April 2012 and compared them with trees under natural drought (ND) in a Mediterranean forest. During the study, we analyzed net CO2 assimilation (A(n)), stomatal conductance (g(s)), transpiration (E), water-use efficiency (WUE), stomatal size and density, density of glandular trichomes and non-glandular trichomes, thickness of the different leaf tissues, specific leaf area and leaf surface. Under AD, tree functioning was slightly impacted, since only A(n) exhibited a 49% drop, while g(s), E and WUE remained stable. The decrease in A(n) under AD was regulated by concomitant lower stomatal density and reduced leaf thickness. Trees under AD also featured leaves with a higher non-glandular trichome density and a lower glandular trichome density compared with ND, which simultaneously limits transpiration and production costs. This study points out that Q. pubescens exhibits adjustments of leaf morpho-anatomical traits which can help trees to acclimate to AD scenarios as those expected in the future in the Mediterranean region.
Auteurs, date et publication :
Auteurs Justine Laoue , Guillermo Gea-Izquierdo , Sylvie Dupouyet , Maria Conde , Catherine Fernandez , Elena Ormeno
Publication : TREE PHYSIOLOGY
Date : 2024
Volume : 44
Issue : 5
Catégorie(s)
#ANR-Citation #CNRS #FORET O3HPRésumé
Abstract
Fundamental axes of variation in plant traits result from trade-offs between costs and benefits of resource-use strategies at the leaf scale. However, it is unclear whether similar trade-offs propagate to the ecosystem level. Here, we test whether trait correlation patterns predicted by three well-known leaf- and plant-level coordination theories – the leaf economics spectrum, the global spectrum of plant form and function, and the least-cost hypothesis – are also observed between community mean traits and ecosystem processes. We combined ecosystem functional properties from FLUXNET sites, vegetation properties, and community mean plant traits into three corresponding principal component analyses. We find that the leaf economics spectrum (90 sites), the global spectrum of plant form and function (89 sites), and the least-cost hypothesis (82 sites) all propagate at the ecosystem level. However, we also find evidence of additional scale-emergent properties. Evaluating the coordination of ecosystem functional properties may aid the development of more realistic global dynamic vegetation models with critical empirical data, reducing the uncertainty of climate change projections.
Auteurs, date et publication :
Auteurs Ulisse Gomarasca , Mirco Migliavacca , Jens Kattge , Jacob A. Nelson , Ülo Niinemets , Christian Wirth , Alessandro Cescatti , Michael Bahn , Richard Nair , Alicia T. R. Acosta , M. Altaf Arain , Mirela Beloiu , T. Andrew Black , Hans Henrik Bruun , Solveig Franziska Bucher , Nina Buchmann , Chaeho Byun , Arnaud Carrara , Adriano Conte , Ana C. Da Silva
Publication : Nature Communications
Date : 2023
Volume : 14
Issue : 1
Pages : 3948
Catégorie(s)
#CNRSRésumé
Abstract Leaf and wood separation is a key step to allow a new range of estimates from Terrestrial LiDAR data, such as quantifying above-ground biomass, leaf and wood area and their 3D spatial distributions. We present a new method to separate leaf and wood from single tree point clouds automatically. Our approach combines unsupervised classification of geometric features and shortest path analysis. The automated separation algorithm and its intermediate steps are presented and validated. Validation consisted of using a testing framework with synthetic point clouds, simulated using ray-tracing and 3D tree models and 10 field scanned tree point clouds. To evaluate results we calculated accuracy, kappa coefficient and F-score. Validation using simulated data resulted in an overall accuracy of 0.83, ranging from 0.71 to 0.94. Per tree average accuracy from synthetic data ranged from 0.77 to 0.89. Field data results presented and overall average accuracy of 0.89. Analysis of each step showed accuracy ranging from 0.75 to 0.98. F-scores from both simulated and field data were similar, with scores from leaf usually higher than for wood. Our separation method showed results similar to others in literature, albeit from a completely automated workflow. Analysis of each separation step suggests that the addition of path analysis improved the robustness of our algorithm. Accuracy can be improved with per tree parameter optimization. The library containing our separation script can be easily installed and applied to single tree point cloud. Average processing times are below 10 min for each tree.
Auteurs, date et publication :
Auteurs Matheus B. Vicari , Mathias Disney , Phil Wilkes , Andrew Burt , Kim Calders , William Woodgate
Publication : Methods in Ecology and Evolution
Date : 2025
Catégorie(s)
#CNRS #FORET NouraguesRésumé
The domain of the Haute-Provence Observatory (OHP) : hermas and downy oak forest, from the XVIII century to now The 95 hectares area of the Observatoire de Haute-Provence (OHP, Observatory of Haute-Provence, an astronomical observatory) has been the property of the National Centre for Scientific Research (CNRS) since 1939. This domain is located in the rural community of Saint-Michel-l’Observatoire, in the département of Alpes-de- Haute-Provence. The climate is subhumid supramediterranean with a mean annual rainfall of 830 mm. The OHP hosts a variety of plant formations typical of the Haute-Provence landscape : most of it is a coppice of Downy Oak (Quercus pubescens) on a soil of compact limestone. In this work we trace the evolution of the land use and property, of the agricultural practices and of the vegetation since the XVIIIth century. We show that the current landscape is the complex product of the agricultural practices that did not change notably until the first half of the XXth century, and remained within the property of a single owner until now. The poorness of the soils, the evolution of the land from “hermas” (agricultural soils that are not cultivated) to the downy oak coppices, and the specific tax system in Provence until the XIXth century can explain the present landscape. This study has been made within the framework of the Oak Observatory at OHP (O3HP), a recent and innovative facility for the study of the dynamics of the Downy Oak forest under the stress of climate change.
Auteurs, date et publication :
Auteurs Chantal Hilaire , Jean-Philippe Orts , Michel Boer , Thierry Gauquelin
Publication : Courrier scientifique du Parc naturel régional du Luberon et de la Réserve de biosphère Luberon-Lure
Date : 2025
Issue : 11
Pages : 8-21
Catégorie(s)
#CNRS #FORET O3HPAuteurs, date et publication :
Auteurs Matthieu Noucher
Publication : Zilsel
Date : 2025
Volume : 2
Issue : 13
Pages : 241-258
Catégorie(s)
#CNRS #FORET NouraguesRésumé
In the past two decades, repeated discoveries of numerous geometric earthworks in interfluvial regions of Amazonia have shed new light onto the territorial extent and the long-term impact of pre-Columbian populations on contemporary landscapes. In particular, the recent development of LiDAR imagery has accelerated the discovery of earthworks in densely forested hinterlands throughout the Amazon basin and the Guiana Shield. This study aimed to evaluate the extent and landscape-scale spatial variations of pre-Columbian disturbances at three ring ditch sites in the French Guiana hinterland. We carried out extensive soil surveys along approximately 1 km-long transects spanning from ring ditches through the surrounding landscapes, and drawn upon multiple indicators, including archaeological artifacts, macroand micro-charcoals, soil colorimetry, and physicochemical properties to retrace the preColumbian history of these sites in terms of occupation periods, anthropogenic soil alteration, and ancient land use. Our results revealed a perennial occupation of these sites over long periods ranging from the 5th and 15th centuries CE, with local enrichments in chemical indicators (Corg, N, Mg, K, Ca) both within the enclosures of ring ditches and in the surrounding landscapes. Physicochemical properties variations were accompanied by variations in soil colorimetry, with darker soils within the enclosure of ring ditches in terra-firme areas. Interestingly however, soil properties did not meet all the characteristics of the so-called Amazonian Dark Earths, thus advocating a paradigm shift towards a better integration of Amazonian Brown Earths into the definition of anthropogenic soils in Amazonia. Soil disturbances were also associated to local enrichments in macro- and micro-charcoals that support in situ fire management that could be attributed to forest clearance and/or slash-and-burn cultivation. Taken together, our results support the idea that pre-Columbian societies made extensive use of their landscapes in the interfluvial regions of the French Guiana hinterlands.
Auteurs, date et publication :
Auteurs Marc Testé , Julien Engel , Kevin Mabobet , Mickael Mestre , Louise Brousseau , Christian Reepmeyer
Publication : PLOS ONE
Date : 2024
Volume : 19
Issue : 9
Pages : e0298714
Catégorie(s)
#CNRS #FORET NouraguesRésumé
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 #UGAAuteurs, date et publication :
Auteurs Justine Laoué
Date : 1970