Résumé
Predation is a strong selective pressure generating morphological, physiological and behavioural responses in organisms. As predation risk is often higher during juvenile stages, antipredator defences expressed early in life are paramount to survival. Maternal effects are an efficient pathway to produce such defences. We investigated whether maternal exposure to predator cues during gestation affected juvenile morphology, behaviour and dispersal in common lizards (Zootoca vivipara). We exposed 21 gravid females to saurophagous snake cues for one month while 21 females remained unexposed (i.e. control). We measured body size, preferred temperature and activity level for each neonate, and released them into semi-natural enclosures connected to corridors in order to measure dispersal. Offspring from exposed mothers grew longer tails, selected lower temperatures and dispersed thrice more than offspring from unexposed mothers. Because both tail autotomy and altered thermoregulatory behaviour are common antipredator tactics in lizards, these results suggest that mothers adjusted offspring phenotype to risky natal environments (tail length) or increased risk avoidance (dispersal). Although maternal effects can be passive consequences of maternal stress, our results strongly militate for them to be an adaptive antipredator response that may increase offspring survival prospects.
Auteurs, date et publication :
Auteurs Elvire Bestion , Aimeric Teyssier , Fabien Aubret , Jean Clobert , Julien Cote
Publication : Proceedings of the Royal Society B: Biological Sciences
Date : 2025
Volume : 281
Issue : 1792
Catégorie(s)
#CNRS #Metatron terrestreRésumé
Abstract
Mapping tropical forest aboveground biomass (AGB) is important for quantifying emissions from land use change and evaluating climate mitigation strategies but remains a challenging problem for remote sensing observations. Here, we evaluate the capability of mapping AGB across a dense tropical forest using tomographic Synthetic Aperture Radar (TomoSAR) measurements at P-band frequency that will be available from the European Space Agency’s BIOMASS mission in 2024. To retrieve AGB, we compare three different TomoSAR reconstruction algorithms, back-projection (BP), Capon, and MUltiple SIgnal Classification (MUSIC), and validate AGB estimation from models using TomoSAR variables: backscattered power at 30 m height, forest height (FH), backscatter power metric (Q), and their combination. TropiSAR airborne campaign data in French Guiana, inventory plots, and airborne LiDAR measurements are used as reference data to develop models and calculate the AGB estimation uncertainty. We used univariate and multivariate regression models to estimate AGB at 4-ha grid cells, the nominal resolution of the BIOMASS mission. Our results show that the BP-based variables produced better AGB estimates compared to their counterparts, suggesting a more straightforward TomoSAR processing for the mission. The tomographic FH and AGB estimation have an average relative uncertainty of less than 10% with negligible systematic error across the entire biomass range (~ 200–500 Mg ha
−1
). We show that the backscattered power at 30 m height at HV polarization is the best single measurement to estimate AGB with significantly better accuracy than the LiDAR height metrics, and combining it with FH improved the accuracy of AGB estimation to less than 7% of the mean. Our study implies that using multiple information from P-band TomoSAR data from the BIOMASS mission provides a new capability to map tropical forest biomass and its changes accurately.
Auteurs, date et publication :
Auteurs Naveen Ramachandran , Sassan Saatchi , Stefano Tebaldini , Mauro Mariotti d’Alessandro , Onkar Dikshit
Publication : Scientific Reports
Date : 2023
Volume : 13
Issue : 1
Pages : 6233
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouAuteurs, date et publication :
Auteurs Shengli Tao , Nicolas Labrière , Kim Calders , Fabian Jörg Fischer , E. Rau , Laetitia Plaisance , Jérôme Chave
Publication : Annals of Forest Science
Date : 2025
Volume : 78
Issue : 4
Pages : 1-13
Catégorie(s)
#ANR-Citation #CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs JC Gibson , FJ Larabee , A Touchard , J Orivel , AV Suarez
Publication : Journal of Zoology
Date : 2025
Volume : 306
Issue : 2
Pages : 119-128
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Tree transpiration depends on biotic and abiotic factors that might change in the future, including precipitation and soil moisture status. Although short-term sap flux responses to soil moisture and evaporative demand have been the subject of attention before, the relative sensitivity of sap flux to these two factors under long-term changes in soil moisture conditions has rarely been determined experimentally. We tested how long-term artificial change in soil moisture affects the sensitivity of tree-level sap flux to daily atmospheric vapor pressure deficit (VPD) and soil moisture variations, and the generality of these effects across forest types and environments using four manipulative sites in mature forests. Exposure to relatively long-term (two to six years) soil moisture reduction decreases tree sap flux sensitivity to daily VPD and relative extractable water (REW) variations, leading to lower sap flux even under high soil moisture and optimal VPD. Inversely, trees subjected to long-term irrigation showed a significant increase in their sensitivity to daily VPD and REW, but only at the most water-limited site. The ratio between the relative change in soil moisture manipulation and the relative change in sap flux sensitivity to VPD and REW variations was similar across sites suggesting common adjustment mechanisms to long-term soil moisture status across environments for evergreen tree species. Overall, our results show that long-term changes in soil water availability, and subsequent adjustments to these novel conditions, could play a critical and increasingly important role in controlling forest water use in the future.
Auteurs, date et publication :
Auteurs Charlotte Grossiord , Sanna Sevanto , Jean-Marc Limousin , Patrick Meir , Maurizio Mencuccini , Robert E. Pangle , William T. Pockman , Yann Salmon , Roman Zweifel , Nate G. McDowell
Publication : Environmental and Experimental Botany
Date : 2025
Volume : 152
Pages : 19-27
Catégorie(s)
#CNRS #FORET PuechabonRésumé
This paper introduces the CASINO (CAnopy backscatter estimation, Subsampling, and Inhibited Nonlinear Optimisation) algorithm for above-ground biomass (AGB) estimation in tropical forests using P-band (435 MHz) synthetic aperture radar (SAR) data. The algorithm has been implemented in a prototype processor for European Space Agency's (ESA's) 7th Earth Explorer Mission BIOMASS, scheduled for launch in 2023. CASINO employs an interferometric ground cancellation technique to estimate canopy backscatter (CB) intensity. A power law model (PLM) is then used to model the dependence of CB on AGB for a large number of systematically distributed SAR data samples and a small number of calibration areas with a known AGB. The PLM parameters and AGB for the samples are estimated simultaneously within pre-defined intervals using nonlinear minimisation of a cost function. The performance of CASINO is assessed over six tropical forest sites on two continents: two in French Guiana, South America and four in Gabon, Africa, using SAR data acquired during airborne ESA campaigns and processed to simulate BIOMASS acquisitions. Multiple tests with only two randomly selected calibration areas with AGB > 100 t/ha are conducted to assess AGB estimation performance given limited reference data. At 2.25 ha scale and using a single flight heading, the root-mean-square difference (RMSD) is ≤ 27% for at least 50% of all tests in each test site and using as reference AGB maps derived from airborne laser scanning data. An improvement is observed when two flight headings are used in combination. The most consistent AGB estimation (lowest RMSD variation across different calibration sets) is observed for test sites with a large AGB interval and average AGB around 200–250 t/ha. The most challenging conditions are in areas with AGB < 200 t/ha and large topographic variations. A comparison with 142 1 ha plots distributed across all six test sites and with AGB estimated from in situ measurements gives an RMSD of 20% (66 t/ha).
Auteurs, date et publication :
Auteurs Maciej J. Soja , Shaun Quegan , Mauro M. d’Alessandro , Francesco Banda , Klaus Scipal , Stefano Tebaldini , Lars M. H. Ulander
Publication : Remote Sensing of Environment
Date : 2021
Volume : 253
Pages : 112153
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
It is well established that the abundances of nitrogen (N) transforming microbes are strongly influenced by land-use intensity in lowland grasslands. However, their responses to management change in less productive and less fertilized mountain grasslands are largely unknown. We studied eight mountain grasslands, positioned along gradients of management intensity in Austria, the UK, and France, which differed in their historical management trajectories. We measured the abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) as well as nitrite-reducing bacteria using specific marker genes. We found that management affected the abundance of these microbial groups along each transect, though the specific responses differed between sites, due to different management histories and resulting variations in environmental parameters. In Austria, cessation of management caused an increase in nirK and nirS gene abundances. In the UK, intensification of grassland management led to 10-fold increases in the abundances of AOA and AOB and doubling of nirK gene abundance. In France, ploughing of previously mown grassland caused a 20-fold increase in AOA abundance. Across sites the abundance of AOB was most strongly related to soil NO3--N availability, and AOA were favoured by higher soil pH. Among the nitrite reducers, nirS abundance correlated most strongly with N parameters, such as soil NO3--N, microbial N, leachate NH4+-N, while the abundance of nirK-denitrifiers was affected by soil total N, organic matter (SOM) and water content. We conclude that alteration of soil environmental conditions is the dominant mechanism by which land management practices influence the abundance of each group of ammonia oxidizers and nitrite reducers.
Auteurs, date et publication :
Auteurs Ute Szukics , Karl Grigulis , Nicolas Legay , Eva-Maria Kastl , Catherine Baxendale , Richard D. Bardgett , Jean-Christophe Clément , Sandra Lavorel , Michael Schloter , Michael Bahn
Publication : Science of The Total Environment
Date : 2025
Volume : 648
Pages : 745-753
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs Phyllis D Coley , María‐José Endara , Gabrielle Ghabash , Catherine A Kidner , James A Nicholls , R Toby Pennington , Anthony G Mills , Abrianna J Soule , Maristerra R Lemes , Graham N Stone
Publication : Journal of Ecology
Date : 2025
Volume : 107
Issue : 4
Pages : 1620-1632
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Harlequin toads (Atelopus spp.) constitute one of the most threatened amphibian clades worldwide, yet much of their life history remains poorly understood. These anurans are strongly associated with stream environments, which are used for reproduction and occupied by males throughout the year, while only visited by females during the reproduction season. We studied a population of the Atelopus flavescens complex in French Guiana. We describe male population density, habitat use, site fidelity and movement, as well as home range behaviour – all prior to the arrival of females. We also present further natural history observations such as nocturnal resting sites and anecdotal observations of females. Our findings suggest that in this lowland population of Atelopus, males maintain territories for a relatively long time compared to other species. Within them, they acoustically compete for females, which they attempt to clasp for amplexus when they arrive later in the season on their way to the breeding sites.
Auteurs, date et publication :
Auteurs Max Ringler
Publication : Salamandra
Date : 2025
Catégorie(s)
#⛔ No DOI found #ANR-Citation #CNRS #FORET NouraguesRésumé
Pre-copulatory female mate choice based on male ultraviolet (UV) coloration has been demonstrated in several vertebrate species; however, post-copulatory mechanisms have been largely overlooked. Here, we investigated female mate preference based on male UV coloration in the common lizard Zootoca vivipara, in which males display conspicuous UV coloration on their throat. During two successive years, we staged sequential mating trials between females and four different males with UV-reduced or control belly and throat coloration. We recorded pre-copulatory female behaviour, copulation behaviour and assigned paternity to all offspring. Females were more aggressive towards UV-reduced males and, during the second year, UV-reduced males had a lower probability of siring at least one egg (fertilization success) during the last mating trials. However, in the second year, copulation was shorter with control males. Altogether, our results suggest that females exert subtle pre-copulatory mate preference based on male UV ornaments and, conditional on the study year and female mating history, some degree of post-copulatory preference for UV-control males leading to differential male fertilization success. This study suggests that UV-based female mate choice may be more widespread than previously thought in vertebrates, and emphasizes the importance of using a study design well adapted to the species reproductive behaviour.
Auteurs, date et publication :
Auteurs Arnaud Badiane , Melissa Martin , Sandrine Meylan , Murielle Richard , Beatriz Decenciere Ferrandiere , Jean-Francois Le Galliard
Publication : BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY
Date : 2020
Volume : 130
Issue : 3
Pages : 586-598