Résumé

Landscape heterogeneity is known as a major factor of community structure and composition. Whether this effect of the landscape extends at different scales and particularly at the relevant scale for microorganisms remained to be determined. We used th

Auteurs, date et publication :

Auteurs Joey Allen , Marion Sire , Nadege Belouard , Caroline Gorzerino , Marie-Agnes Coutellec , Cendrine Mony , Alexandrine Pannard , Christophe Piscart

Date : 2025

Catégorie(s)

#CNRS #EcoGenO #Université de Rennes

Auteurs, date et publication :

Auteurs David Dumoulin Kervran

Publication : Zilsel

Date : 2025

Volume : N° 14

Issue : 1

Pages : 293-311

Catégorie(s)

#CNRS #FORET Nouragues

Résumé

Fine roots mediate plant nutrient acquisition and growth. Depending on soil nutrient availability, plants can regulate fine root biomass and morphological traits to optimise nutrient acquisition. Little is known, however, about the importance of these parameters influencing forest functioning. In this study, we measured root responses to nutrient additions to gain a mechanistic understanding of plant adaptations to nutrient limitation in two tropical forests in French Guiana, differing twofold in their soil nutrient statuses. We analysed the responses of root biomass, mean root diameter (RD), specific root length (SRL), specific root area (SRA), root tissue density (RTD) and carbon (C), nitrogen (N) and phosphorus (P) concentrations in roots down to 15 cm soil depth after three years of N and P additions. At the lower-fertility site Paracou, no changes in root biomass or morphological traits were detected with either N or P addition, although P concentrations in roots increased with P addition. In the higher fertility site, Nouragues, root biomass and P concentrations in roots increased with P addition, with no changes in morphological traits. In contrast, N addition shifted root traits from acquisitive to more conservative by increasing RTD. A significant interaction between N and P in Nouragues pointed to stronger responses to P addition in the absence of N. Our results suggest that the magnitude and direction of root biomass and trait expression were regulated by soil fertility, corroborated by the response to N or P additions. At low fertility sites, we found lower plasticity in root trait expression compared to more fertile conditions, where N and P additions caused stronger and antagonistic responses. Identifying the exact role of mechanisms affecting root nutrient uptake in Amazon forests growing in different soils will be crucial to foresee if and how rapid global changes can affect their carbon allocation.

Auteurs, date et publication :

Auteurs Laynara F. Lugli , Lucia Fuchslueger , Helena Vallicrosa , Leandro Van Langenhove , Christian Ranits , Pere Roc Fernandez Garberi , Lore Verryckt , Oriol Grau , Laëtitia Bréchet , Guille Peguero , Joan Llusia , Romà Ogaya , Laura Marquez , Miguel Portillo-Estrada , Irene Ramirez-Rojas , Elodie Courtois , Clement Stahl , Jordi Sardans , Josep Penuelas , Erik Verbruggen

Publication : Oikos

Date : 2025

Volume : 2024

Issue : 4

Pages : e10412

Catégorie(s)

#ANR-Citation #CNRS #FORET Nouragues #FORET Paracou

Résumé

An important question in evolutionary biology is to identify the mechanisms that control the number of reproductives in social groups. Ants are appropriate models to address this question because of the variety of their social structures both within and between species, making this taxon suitable for initiating comparative studies to examine the drivers of this diversity. In this study, we developed a comparative approach between populations of the ponerine ant Odontomachus hastatus from Brazil and French Guiana. In Brazil, monogynous and polygynous colonies coexist in the same populations, whereas only monogynous colonies are present in French Guiana. We combined ecological, behavioural and chemical analyses to identify the factors associated with the expression of this social polymorphism. In Brazil, nest densities were higher than in French Guiana, but nesting sites were available in large quantities in both areas, indicating that habitat saturation is probably not the cause of social polymorphism. We did not detect any difference in queen size, regardless of the social structure of the colonies, suggesting that dispersal strategies may be similar between monogynous and polygynous populations. We found no influence of social structure on aggression intensity in dyadic encounters between workers. Last, we showed that the level of aggression increased with both geographical and chemical distance, but we did not find any difference in cuticular profiles between monogynous and polygynous colonies. Overall, the determinism of social polymorphism in O. hastatus still eludes us and calls for further field experiments coupled with genetic approaches.

Auteurs, date et publication :

Auteurs C. Bottcher , K. Berthelot , A. Bernadou , J. Orivel , V. Fourcassié , P. S. Oliveira , R. Jeanson

Publication : Insectes Sociaux

Date : 2025

Volume : 71

Issue : 1

Pages : 61-73

Catégorie(s)

#CNRS #FORET Nouragues

Résumé

Mountain shrublands are widespread habitats of the European Alps. Shrub encroachment into above treeline grazed lands profoundly modifies biodiversity and ecosystem functioning. Yet, mountain shrublands remain overlooked in vegetation distribution modeling because it is difficult to distinguish them from productive grasslands. Here, we used the pigment-sensitive spectral indices based on Sentinel-2 bands within a specific phenological window, to produce a high-resolution distribution map of mountain shrublands in the French Alps. We evaluated the performance of our classification using a large dataset of vegetation plots and found that our model is highly sensitive to Ericaceous species which constitute most of the dense alpine shrublands in the French Alps. Our analysis of topoclimatic and land use factors limiting the shrubland distribution at regional scale found that, consistent with the ecophysiology of shrubs, expansion is limited by a combination of water deficit and temperature. We discussed the past and current land-use implications in the observed distribution and put forward hypotheses combining climate and land-use trajectories. Our work provides a baseline for monitoring mountain shrub dynamics and exploring the response of shrublands to past and ongoing climate and land use changes.

Auteurs, date et publication :

Auteurs Arthur Bayle , Bradley Z. Carlson , Baptiste Nicoud , Loïc Francon , Christophe Corona , Sandra Lavorel , Philippe Choler

Publication : Frontiers of Biogeography

Date : 2025

Volume : 16

Issue : 1

Catégorie(s)

#CNRS #Lautaret #UGA

Résumé

The importance of biota to soil formation and landscape development is widely recognized. As biotic complexity increases during early succession via colonization by soil microbes followed by vascular plants, effects of biota on mineral weathering and soil formation become more complex. Knowledge of the interactions among groups of organisms and environmental conditions will enable us to better understand landscape evolution. Here, we used experimental columns of unweathered granular basalt to investigate how early successional soil microbes, vascular plants (alfalfa; Medicago sativa), and soil moisture interact to affect both plant performance and mineral weathering. We found that the presence of soil microbes reduced plant growth rates, total biomass, and survival, which suggests that plants and microbes were competing for nutrients in this environment. However, we also found considerable genotype-specific variation in plant–microbial interactions, which underscores the importance of within-species genetic variation on biotic interactions. We also found that the presence of vascular plants reduced variability in pH and electrical conductivity, suggesting that plants may homogenize weathering reactions across the soil column. We also show that there is heterogeneity in the abiotic conditions in which microbes, plants, or their combination have the strongest effect on weathering, and that many of these relationships are sensitive to soil moisture. Our findings highlight the importance of interdependent effects of environmental and biotic factors on weathering during initial landscape formation.

Auteurs, date et publication :

Auteurs Valerie R. Milici , Samuel Abiven , Hannes H. Bauser , Lily G. Bishop , Rebecca G. W. Bland , Jon Chorover , Katerina M. Dontsova , Kielah Dyer , Linus Friedman , Matthew J. Rusek-Peterson , Scott Saleska , Katrina M. Dlugosch

Publication : Geobiology

Date : 2025

Volume : 22

Issue : 6

Pages : e70004

Catégorie(s)

#CNRS #Ecotron de Montpellier #Ecotron IleDeFrance #ENS

Résumé

NATURE-BASED SOLUTIONS: An important lever for mitigating climate change, only if they come with a drastic reduction in greenhouse gas emissions Ongoing climate change calls for strong responses, in particular to reduce greenhouse gas emissions. However, even a drastic reduction in greenhouse gas emissions will not enable to achieve the targets set by the Paris Agreement of global warming below 2 °C, a fortiori 1.5°C. This objective is still achievable if the imperative reduction in emissions is accompanied by the implementation of negative emission technologies aiming at transferring and storing the carbon dioxide from the atmosphere into a different form that has no impact on the climate. These technologies include nature-based solutions. In this article, we present part of the available portfolio on land surfaces by summarizing the literature. We present their potential and their limitations, and recall the importance of an integrated vision of ecosystem management, which needs to be multi-objective.

Auteurs, date et publication :

Auteurs B Guenet , J Le Noë

Publication : Etude et Gestion des Sols

Date : 2025

Volume : 31

Catégorie(s)

#CNRS #Ecotron de Montpellier #ENS

Résumé

Many plant species have dorsiventral leaves that have significant differences in optical properties from one side to the other. Several studies have revealed that ignoring this asymmetry induces significant errors in plant canopy reflectance, and current leaf models simulating leaf dorsiventrality are limited to the 0.4–2.5 μm wavelength range. This article, partly based on two recently collected datasets in the 2.5–14 μm wavelength range, demonstrates that ignoring leaf dorsiventrality induces significant errors in brightness temperature and effective emissivity at the canopy scale. The PROLIB model, which inherits from the PROSPECT-VISIR and LIBERTY models, is the first radiative transfer model to simulate the reflectance and transmittance of both leaf sides from 0.4 to 5.7 μm. The palisade and spongy mesophylls are represented as plate and sphere layers, respectively, to account for the structural asymmetry of leaf cells. The sieve effect that explains the differences in transmittance between the adaxial and abaxial sides of the leaf is successfully incorporated into PROLIB. Evaluation of the model on several leaf datasets shows that: (1) It reproduces well the adaxial and abaxial optical properties of the leaves, with a root mean square error (RMSE) of 0.0109 for reflectance and transmittance. (2) It can be inversed to retrieve leaf traits, with RMSE values for leaf chlorophyll, carotenoid, anthocyanin, water, and dry matter content of 5.519 μg/cm2, 2.344 μg/cm2, 4.219 μg/cm2, 0.0022 g/cm2, and 0.0017 g/cm2, respectively (corresponding normalized RMSE values of 22.0%, 34.0%, 49.4%, 19.6%, and 24.7%). However, better and more complete leaf datasets are needed for leaf dorsiventrality analysis and model calibration.

Auteurs, date et publication :

Auteurs Hanyu Shi , Stéphane Jacquemoud , Jingyi Jiang , Minqiang Zhou , Sophie Fabre , Andrew D. Richardson , Shuang Wang , Xuju Jiang , Zhiqiang Xiao

Publication : Remote Sensing of Environment

Date : 2025

Volume : 306

Pages : 114140

Catégorie(s)

#CNRS #FORET Nouragues

Résumé

The future of tropical forests hinges on the balance between disturbance rates, which are expected to increase with climate change, and tree growth. Whereas tree growth is a slow process, disturbance events occur sporadically and tend to be short-l­ived. This difference challenges forest monitoring to achieve sufficient resolution to capture tree growth, while covering the necessary scale to characterize disturbance rates. Airborne LiDAR time series can address this challenge by measuring landscape scale changes in canopy height at 1 m resolution. In this study, we present a robust framework for analysing disturbance and recovery processes in LiDAR time series data. We apply this framework to 8000 ha of old-g­ rowth tropical forests over a 4–5-­ year time frame, comparing growth and disturbance rates between Borneo, the eastern Amazon and the Guiana shield. Our findings reveal that disturbance was balanced by growth in eastern Amazonia and the Guiana shield, resulting in a relatively stable mean canopy height. In contrast, tall Bornean forests experienced a decrease in canopy height due to numerous small-­scale (<0.1 ha) disturbance events outweighing the gains due to growth. Within sites, we found that disturbance rates were weakly related to topography, but significantly increased with maximum canopy height. This could be because taller trees were particularly vulnerable to disturbance agents such as drought, wind and lightning. Consequently, we anticipate that tall forests, which contain substantial carbon stocks, will be disproportionately affected by the increasing severity of extreme weather events driven by climate change.

Auteurs, date et publication :

Auteurs Toby D. Jackson , Fabian J. Fischer , Grégoire Vincent , Eric B. Gorgens , Michael Keller , Jérôme Chave , Tommaso Jucker , David A. Coomes

Publication : Global Change Biology

Date : 2025

Volume : 30

Issue : 9

Pages : e17493

Catégorie(s)

#CNRS #FORET Nouragues

Résumé

The fundamental trade-off between current and future reproduction has long been considered to result in a tendency for species that can grow large to begin reproduction at a larger size. Due to the prolonged time required to reach maturity, estimates of tree maturation size remain very rare and we lack a global view on the generality and the shape of this trade-off. Using seed production from five continents, we estimate tree maturation sizes for 486 tree species spanning tropical to boreal climates. Results show that a species' maturation size increases with maximum size, but in a non-proportional way: the largest species begin reproduction at smaller sizes than would be expected if maturation were simply proportional to maximum size. Furthermore, the decrease in relative maturation size is steepest in cold climates. These findings on maturation size drivers are key to accurately represent forests' responses to disturbance and climate change.

Auteurs, date et publication :

Auteurs Valentin Journé , Michał Bogdziewicz , Benoit Courbaud , Georges Kunstler , Tong Qiu , Marie‐Claire Aravena Acuña , Davide Ascoli , Yves Bergeron , Daniel Berveiller , Thomas Boivin , Raul Bonal , Thomas Caignard , Maxime Cailleret , Rafael Calama , J. Julio Camarero , Chia‐Hao Chang‐Yang , Jerome Chave , Francesco Chianucci , Thomas Curt , Andrea Cutini

Publication : Ecology Letters

Date : 2025

Volume : 27

Issue : 9

Pages : e14500

Catégorie(s)

#CNRS #FORET OPTMix #FORET Puechabon #INRAE