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[hal-03807910] Co-limitation towards lower latitudes shapes global forest diversity gradients
The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers.
ano.nymous@ccsd.cnrs.fr.invalid (Jingjing Liang) 06 Jul 2023
https://hal.inrae.fr/hal-03807910v1
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[hal-03554126] The number of tree species on Earth
One of the most fundamental questions in ecology is how many species inhabit the Earth. However, due to massive logistical and financial challenges and taxonomic difficulties connected to the species concept definition, the global numbers of species, including those of important and well-studied life forms such as trees, still remain largely unknown. Here, based on global ground-sourced data, we estimate the total tree species richness at global, continental, and biome levels. Our results indicate that there are ∼73,000 tree species globally, among which ∼9,000 tree species are yet to be discovered. Roughly 40% of undiscovered tree species are in South America. Moreover, almost one-third of all tree species to be discovered may be rare, with very low populations and limited spatial distribution (likely in remote tropical lowlands and mountains). These findings highlight the vulnerability of global forest biodiversity to anthropogenic changes in land use and climate, which disproportionately threaten rare species and thus, global tree richness.
ano.nymous@ccsd.cnrs.fr.invalid (Roberto Cazzolla Gatti) 31 May 2022
https://hal.inrae.fr/hal-03554126v1
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[hal-03873631] High exposure of global tree diversity to human pressure
Safeguarding Earth’s tree diversity is a conservation priority due to the importance of trees for biodiversity and ecosystem functions and services such as carbon sequestration. Here, we improve the foundation for effective conservation of global tree diversity by analyzing a recently developed database of tree species covering 46,752 species. We quantify range protection and anthropogenic pressures for each species and develop conservation priorities across taxonomic, phylogenetic, and functional diversity dimensions. We also assess the effectiveness of several influential proposed conservation prioritization frameworks to protect the top 17% and top 50% of tree priority areas. We find that an average of 50.2% of a tree species’ range occurs in 110-km grid cells without any protected areas (PAs), with 6,377 small-range tree species fully unprotected, and that 83% of tree species experience nonnegligible human pressure across their range on average. Protecting high-priority areas for the top 17% and 50% priority thresholds would increase the average protected proportion of each tree species’ range to 65.5% and 82.6%, respectively, leaving many fewer species (2,151 and 2,010) completely unprotected. The priority areas identified for trees match well to the Global 200 Ecoregions framework, revealing that priority areas for trees would in large part also optimize protection for terrestrial biodiversity overall. Based on range estimates for >46,000 tree species, our findings show that a large proportion of tree species receive limited protection by current PAs and are under substantial human pressure. Improved protection of biodiversity overall would also strongly benefit global tree diversity.
ano.nymous@ccsd.cnrs.fr.invalid (Wen-Yong Guo) 28 Nov 2022
https://hal.science/hal-03873631v1
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[hal-03772046] Seasonal variation of leaf thickness: An overlooked component of functional trait variability
The dry and wet seasons in the Neotropics have strong effects on soil water and nutrient availability, as well as on forest dynamics. Despite these major effects on forest ecology, little is known on how leaf traits vary throughout the seasons in tropical rainforest trees. • Here, we investigated the influence of seasonal variations in climate and soil characteristics on leaf trait variation in two tropical tree species. We measured two leaf traits, thickness and water mass per area, in 401 individuals of two species of Symphonia (Clusiaceae) in the Paracou research station in French Guiana tropical lowland rainforest. • We found a significant effect of seasonal variation on these two leaf traits. Soil relative extractable water was a strong environmental predictor of leaf trait variation in response to seasonal variation. Reduced soil water availability during the dry season was associated with increased leaf thickness and water mass per area, possibly as a result of stomatal closure. • Our findings advocate the need to account for environmental seasonality when studying leaf traits in seasonal ecosystems such as tropical forests.
ano.nymous@ccsd.cnrs.fr.invalid (S. Schmitt) 18 Sep 2024
https://hal.inrae.fr/hal-03772046v1
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[hal-04099989] On a agrandi la structure du bois en 3D : un projet collaboratif de science ouverte
Le bois est un matériau cellulaire complexe par son hétérogénéité et sa variabilité. Le premier niveau de variabilité est celui de l’espèce, laquelle pilote l’organisation du plan ligneux, qui lui est spécifique. Mais au sein d’une même espèce, au même bagage génétique, chaque arbre a son propre mode de croissance, de formation du bois, lesquels sont alors fortement dépendant de la région, de la placette, dans laquelle il se développe mais aussi de l’environnement local de l’individu. Enfin, chaque année, chaque saison impose ses conditions environnementales de croissance qui vont moduler les processus biologiques. A cela se rajoutent les spécificités locales du bois liées à des développements particuliers tels que les noeuds, la présence de bois de réaction, etc. Mais, finalement, même parmi ceux qui travaillent le bois quotidiennement, peu sont ceux qui ont l’occasion de passer des heures sous un microscope pour apprécier toute cette complexité et cette diversité de structures. Et nombreux sont pourtant les enseignants, en lycée, à l’université, dans une école d’ingénieur de sciences du bois, qui souhaitent faire observer ces fascinantes structures à leurs élèves. Il existe maintenant une solution théoriquement simple, un peu plus complexe à mettre en oeuvre, qui permet de mettre dans les mains de tous, un objet, copie conforme d’une structure anatomique de bois en 3D.
ano.nymous@ccsd.cnrs.fr.invalid (Éric Badel) 17 May 2023
https://hal.inrae.fr/hal-04099989v1
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[hal-03714709] A standardized morpho-functional classification of the planet's humipedons
It was time to take stock. We modified the humipedon classification key published in 2018 to make it easier and more practical. This morpho-functional taxonomy of the topsoil (humipedon) was only available in English; we also translated it into French and Italian. A standardized morpho-functional classification of humipedons (roughly the top 30–40 cm of soil: organic and organomineral surface horizons) would allow for a better understanding of the functioning of the soil ecosystem. This paper provides the founding principles of the classification of humipedon into humus systems and forms. With the recognition of a few diagnostic horizons, all humus systems can be determined. The humus forms that make up these humus systems are revealed by measuring the thicknesses of the diagnostic horizons. In the final part of the article, several figures represent the screenshots of a mobile phone or tablet application that allows for a fast recall of the diagnostic elements of the classification in the field. The article attempts to promote a standardized classification of humipedons for a global and shared management of soil at planet level.
ano.nymous@ccsd.cnrs.fr.invalid (Augusto Zanella) 11 Jul 2022
https://hal.science/hal-03714709v2
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[hal-03678147] Do <sup>2</sup> H and <sup>18</sup> O in leaf water reflect environmental drivers differently?
We compiled hydrogen and oxygen stable isotope compositions (delta H-2 and delta O-18) of leaf water from multiple biomes to examine variations with environmental drivers. Leaf water delta H-2 was more closely correlated with delta H-2 of xylem water or atmospheric vapour, whereas leaf water delta O-18 was more closely correlated with air relative humidity. This resulted from the larger proportional range for delta H-2 of meteoric waters relative to the extent of leaf water evaporative enrichment compared with delta O-18. We next expressed leaf water as isotopic enrichment above xylem water (Delta H-2 and Delta O-18) to remove the impact of xylem water isotopic variation. For Delta H-2, leaf water still correlated with atmospheric vapour, whereas Delta O-18 showed no such correlation. This was explained by covariance between air relative humidity and the Delta O-18 of atmospheric vapour. This is consistent with a previously observed diurnal correlation between air relative humidity and the deuterium excess of atmospheric vapour across a range of ecosystems. We conclude that H-2 and O-18 in leaf water do indeed reflect the balance of environmental drivers differently; our results have implications for understanding isotopic effects associated with water cycling in terrestrial ecosystems and for inferring environmental change from isotopic biomarkers that act as proxies for leaf water.
ano.nymous@ccsd.cnrs.fr.invalid (Lucas Cernusak) 25 May 2022
https://hal.inrae.fr/hal-03678147v1
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[hal-03518443] Global maps of soil temperature
Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km² resolution for 0-5 and 5-15 cm soil depth. These maps were created by calculating the difference (i.e., offset) between in-situ soil temperature measurements, based on time series from over 1200 1-km² pixels (summarized from 8500 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (-0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in-situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications.
ano.nymous@ccsd.cnrs.fr.invalid (Jonas Lembrechts) 03 Mar 2022
https://hal.science/hal-03518443v1
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[hal-03658479] Traceability and quality assessment of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) logs: the TreeTrace_Douglas database
[...]
ano.nymous@ccsd.cnrs.fr.invalid (Fleur Longuetaud) 31 Jan 2023
https://hal.science/hal-03658479v1
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[hal-04327109] A review of the heterogeneous landscape of biodiversity databases: opportunities and challenges for a synthesized biodiversity knowledge base
Aim Addressing global environmental challenges requires access to biodiversity data across wide spatial, temporal and taxonomic scales. Availability of such data has increased exponentially recently with the proliferation of biodiversity databases. However, heterogeneous coverage, protocols, and standards have hampered integration among these databases. To stimulate the next stage of data integration, here we present a synthesis of major databases, and investigate (a) how the coverage of databases varies across taxonomy, space, and record type; (b) what degree of integration is present among databases; (c) how integration of databases can increase biodiversity knowledge; and (d) the barriers to database integration. Location Global. Time period Contemporary. Major taxa studied Plants and vertebrates. Methods We reviewed 12 established biodiversity databases that mainly focus on geographic distributions and functional traits at global scale. We synthesized information from these databases to assess the status of their integration and major knowledge gaps and barriers to full integration. We estimated how improved integration can increase the data coverage for terrestrial plants and vertebrates. Results Every database reviewed had a unique focus of data coverage. Exchanges of biodiversity information were common among databases, although not always clearly documented. Functional trait databases were more isolated than those pertaining to species distributions. Variation and potential incompatibility of taxonomic systems used by different databases posed a major barrier to data integration. We found that integration of distribution databases could lead to increased taxonomic coverage that corresponds to 23 years’ advancement in data accumulation, and improvement in taxonomic coverage could be as high as 22.4% for trait databases. Main conclusions Rapid increases in biodiversity knowledge can be achieved through the integration of databases, providing the data necessary to address critical environmental challenges. Full integration across databases will require tackling the major impediments to data integration: taxonomic incompatibility, lags in data exchange, barriers to effective data synchronization, and isolation of individual initiatives.
ano.nymous@ccsd.cnrs.fr.invalid (Xiao Feng) 19 Feb 2025
https://hal.inrae.fr/hal-04327109v1
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[hal-03691513] Phénotypage fin de la composition corporelle chez le ruminant :mise au point et calibration de huit méthodes innovantes
[...]
ano.nymous@ccsd.cnrs.fr.invalid (José Pires) 09 Jun 2022
https://hal.science/hal-03691513v1
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[hal-03778748] Comment déterminer l'exposition aux changements climatiques des zones de production forestière française ? Méthodologie utilisée dans le projet ESPERENSE pour cibler les zones d’intérêt pour l’installation d’essais de comparaison d’essences et de provenances
Les dernières observations de dépérissements et l’analyse de leurs causes tendent à confirmer la vulnérabilité de certaines des principales essences forestières françaises vis-à-vis des changements climatiques. Conscients de ces enjeux, les gestionnaires s’interrogent sur la conduite et le renouvellement de leurs peuplements. Le réseau multi organismes ESPERENSE se met en place pour rechercher des réponses à ces interrogations via l’organisation d’un réseau d’essais de comparaison d’essences et de provenances. Afin de rationaliser l'effort expérimental, une méthodologie a été établie pour prioriser les zones du territoire métropolitain dans lesquelles une recherche des alternatives aux essences en place doit être menée. Elle consiste à sélectionner les zones à fort enjeu de production de bois, et qui sont en même temps déjà en situation préoccupante ou qui le seront à l’avenir du fait des évolutions du climat en s’appuyant sur 3 différentes approches de modélisation. Le principe consiste donc à évaluer le risque par la combinaison des enjeux et de leur exposition. La démarche de construction de ce zonage est détaillée. Les cartes résultant de ce travail sont mises à disposition pour les principales essences françaises.
ano.nymous@ccsd.cnrs.fr.invalid (Hedi Kebli) 16 Sep 2022
https://hal.inrae.fr/hal-03778748v1
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[hal-03659201] Mapping tree mortality rate in a tropical moist forest using multi-temporal LiDAR
Background and aims: Several studies have shown an increase in tree mortality in intact tropical forests in recent decades. However, most studies are based on networks of field plots whose representativeness is debated. We examine the potential of repeated Airborne LiDAR Scanning data to map forest structure change over large areas with high spatial resolution and to detect tree mortality patterns at landscape level. Methods: The study site is a complex forested landscape in French Guiana with varied topographic positions, vegetation structures and disturbance history. We computed a Gap Dynamics Index from Canopy Height Models derived from successive LiDAR data sets (2009, 2015 and 2019) that we compared to field-measured mortality rates (in stem number and basal area loss) obtained from regular monitoring of 74 1.56-ha permanent plots. Results: At the plot level, the relation between gap dynamics and absolute basal area loss rate (combining fallen and standing dead trees) was overall highly significant (R 2 = 0.60) and especially tight for the 59 ha of unlogged forest (R 2 = 0.72). Basal area loss rate was better predicted from gap dynamics than stem loss rate. In particular, in previously logged plots, intense self-thinning of small stems did not translate into detectable gaps, leading to poor predictability of stem mortality by LiDAR in those forests severely disturbed 30 years before. At the landscape scale, LiDAR data revealed spatial patterns of gap creation that persisted over the successive analysis periods. Those spatial patterns were related to local topography and canopy height. High canopy forests and bottomlands were more dynamic, with a higher fraction of canopy affected by gaps per unit time indicating higher basal area loss rates. Conclusion: Gap detection and mapping via multitemporal LiDAR data is poised to become instrumental in characterizing landscape-scale forest response to current global change. Meaningful comparison of gap dynamics across time and space will, however, depend on consistent LiDAR acquisitions characteristics.
ano.nymous@ccsd.cnrs.fr.invalid (Claudia Huertas) 04 May 2022
https://hal.inrae.fr/hal-03659201v1
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[hal-03919731] Dendrometric data from the silvicultural scenarios developed by Office National des Forêts (ONF) in France: a tool for applied research and carbon storage estimates
We provide a database of 52 silvicultural scenarios recommended in French public forests including relevant dendrometric variables and metrics for carbon accounting. The dataset is available at https://doi.org/10.57745/QARRFS . Associated metadata are available at https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/f76ed27f-325d-493b-8731-0995dcaa7805 . Special attention was paid to offer carbon metrics required for the French Label Bas Carbone offset projects.
ano.nymous@ccsd.cnrs.fr.invalid (Salomé Fournier) 04 Jul 2023
https://agroparistech.hal.science/hal-03919731v1
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[hal-03519397] Do trait responses to simulated browsing in Quercus robur saplings affect their attractiveness to Capreolus capreolus the following year?
With the rise of large herbivore populations in most northern hemisphere forests, browsing is becoming an increasingly important driver of forest regeneration dynamics. Among other processes affecting the regeneration, the concept of plant-herbivore feedback loops holds that browsed saplings are more subject to subsequent herbivory. This phenomenon is interpreted as a consequence of compensatory growth following browsing since fast growth is generally associated with higher digestibility and lower defense against herbivores. However, studies linking browsing-induced trait variations to subsequent attractiveness to herbivores are still lacking, especially in the forest context. In this study, we experimentally examine the existence of a feedback loop between oak (Quercus robur L.) and roe deer (Capreolus capreolus) and investigate its underlying morphological and chemical traits. We simulated single and repeated roe deer browsing on nursery-grown oak saplings and measured the changes in sapling height growth, lateral branching, leaf traits and winter shoot traits over two years. We conducted winter feeding trials with tame roe deer one year after the first treatment to test the effect of simulated browsing on sapling attractiveness. Simulated browsing reduced sapling height growth but had no effect on branching. Simulated browsing had no effect on leaf traits after half a year, but decreased the phenolic content and increased the fiber content of winter shoots the following winter. Contrary to our predictions, roe deer preferentially browsed control saplings over saplings previously browsed. After two years, repeated browsing promoted fast carbon acquisition leaf traits (high chlorophyll, high specific leaf area and low fiber content), reduced leaf phenolic content and increased leaf digestibility. We showed that a reduction in 1-year-old oak sapling height growth following browsing, combined with increased structural defense at the expense of chemical defense in winter shoots the following winter, was correlated with reduced browsing pressure, thereby challenging the feedback loop hypothesis. However, we also demonstrated that repeated browsing promoted fast carbon acquisition leaf traits in 2.5-year-old saplings, which tend to support the existence of a feedback loop on older and more intensively browsed saplings. As such, our study provides empirical evidence that morphological and physiological trait responses to browsing influence oak sapling attractiveness, but that the direction and magnitude of this effect depend on the ontogenic stage of the sapling and on the number of browsing events.
ano.nymous@ccsd.cnrs.fr.invalid (Julien Barrere) 05 Jan 2024
https://hal.inrae.fr/hal-03519397v1
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[hal-03952163] Early effects of two planting densities on growth dynamics and water-use efficiency in Robinia pseudoacacia (L.) and Populus deltoides (Bartr. ex Marsh.) × P. nigra (L.) short rotation plantations.
As a renewable energy resource, woody biomass has a role to play in reducing worldwide fossil fuel consumption. Species in the genera Salix and Populus are widely used for this purpose through short rotation tree plantations under temperate latitudes. In warmer climates, common short rotation species include genera such as eucalyptus or black locust (Robinia) although this latter is also cultivated in temperate climates. The objective of our study was to compare the potential of poplar (Populus deltoides × P. nigra, clone 'Dorskamp') and black locust (Robinia pseudoacacia, provenances 'Nagybudmerii' and 'Nyirseg') for biomass production in the Northwest of France. We estimated biomass production and efficiency of water use of poplar compared to those of the two provenances of black locust, (1) at two planting densities (short rotation forestry: SRF, 1428 trees per ha vs. short rotation coppice: SRC, 7272 trees per ha), and (2) 2 and 4 years after planting. Only few effects of the initial planting density on plant growth and physiology were visible two years after planting. Stem height and circumference became higher in SRF than in SRC for both species after four years. Yield at plantation level of the first SRC rotation was almost twice as high for black locust than for poplar, while both species exhibited similar stem height or stem increase rate likely due to the development of more sylleptic branches in black locust. At the end of the second rotation, plantation yield was significantly higher for poplar due to black locust mortality. The combination of higher leaf N and greater WUE probably enhanced black locust performance under the dry conditions of our study site in 2010. During the fourth year (2012), the gap between the two species in terms of Δ 13 C, used as a surrogate of water-use efficiency, was less marked than during the first years due to the fact that poplar Δ 13 C decreased (increase in WUE), while black locust Δ 13 C slightly increased (decrease in WUE). To conclude, black locust appears as an interesting option for biomass production at sites prone to water shortage. However, at high planting density, poplar exhibited a lower mortality after harvest leading to an improved biomass production at the end of the second SRC rotation compared to black locust. The choice of species/cultivar must be adapted to the production system (SRC vs. SRF) and to the specific site conditions.
ano.nymous@ccsd.cnrs.fr.invalid (Pierrick Priault) 26 Jan 2023
https://hal.science/hal-03952163v1
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[hal-03778033] Forest management prolongates the CO2 sink in ageing oak stands
Forest management prolongates the CO 2 sink in ageing oak stands. Introduction. Model evaluation.
ano.nymous@ccsd.cnrs.fr.invalid (Soisick Figuères) 15 Sep 2022
https://hal.science/hal-03778033v1
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[hal-03665846] Past and future radial growth and water-use efficiency of Fagus sylvatica and Quercus robur in a long-term climate refugium
The low-latitudinal range margins of many temperate and boreal tree species consist of scattered populations that persist locally in climate refugia. Recent studies have shown that such populations can be remarkably resilient, yet their past resilience does not imply that they are immune to threats from future climate change. The functioning of refugial tree populations therefore needs to be better understood if we are to anticipate their prospects correctly. We performed a detailed study of tree radial growth and vigor in a long-term climate refugial population of beech (Fagus sylvatica), comparing the observed trends with those of co-occurring pedunculate oak (Quercus robur). Annual growth rates (basal area increment, BAI) for both species were similar to those observed in range-core populations, but natural lifespan was half that in the mountains. The master chronologies spanning 1870-2015 revealed 22% (Fagus) and 20% (Quercus) increases in BAI until the 1980s and a smaller decrease (-6% for Fagus,-9% for Quercus) since then. Stable carbon isotope measurements (delta C-13) revealed no effect of cambial age and an increase in water-use efficiency (iWUE) from 1870-2015 of about 50% for Fagus and 20% for Quercus. The trend continued until 2015 in Fagus, whereas Quercus reached its maximum in the 1980s. A detailed analysis of the relationship between climate and annual growth based on a 118-year meteorological record revealed a major role of water availability in the current and previous year. We used the observed climatic relationships to model future growth trends until 2100 for the IPCC scenarios RCP4.5 and RCP8.5. Most projections revealed no change in current growth rates, suggesting that this climate refugium will be able to provide suitable conditions for the persistence of Fagus and Quercus over the coming decades even under warmer and drier regional climate conditions. Overall, our study provides valuable insight into the precise climatic and biological mechanisms enhancing the persistence of refugial tree populations under ongoing climate change.
ano.nymous@ccsd.cnrs.fr.invalid (Didier Bert) 02 Dec 2022
https://hal.inrae.fr/hal-03665846v1
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[hal-03678060] Wind Speed Controls Forest Structure in a Subtropical Forest Exposed to Cyclones: A Case Study Using an Individual-Based Model
Extreme wind blowdown events can significantly modify the structure and composition of forests, and the predicted shift in tropical cyclone regimes due to climate change could strongly impact forests across the tropics. In this study, we coupled an individual-based and spatially-explicit forest dynamics model (TROLL) with a mechanistic model estimating wind damage as a function of tree size, traits, and allometry (ForestGALES). We assimilated floristic trait data and climate data from a subtropical forest site in Taiwan to explore the effect of wind regimes on forest properties. We found that the average canopy height and biomass stocks decreased as wind disturbance strength increased, but biomass stocks showed a nonlinear response. Above a wind intensity threshold, both canopy height and biomass drastically decreased to near-zero, exhibiting a transition to a non-forest state. Wind intensity strongly regulated wind impact, but varying wind frequency did not cause discernible effects. The implementation of within-stand topographic heterogeneity led to weak effects on within-stand forest structure heterogeneity at the study site. In conclusion, the intensity of wind disturbances can potentially greatly impact forest structure by modifying mortality. Individual-based modeling provides a framework in which to investigate the impact of wind regimes on mortality, other factors influencing wind-induced tree mortality, as well as interaction between wind and other forms of forest disturbance and human land use legacy.
ano.nymous@ccsd.cnrs.fr.invalid (E-Ping Rau) 25 May 2022
https://hal.inrae.fr/hal-03678060v1
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[hal-03502713] Uncovering the critical soil moisture thresholds of plant water stress for European ecosystems
Understanding the critical soil moisture (SM) threshold (θcrit) of plant water stress and land surface energy partitioning is a basis to evaluate drought impacts and improve models for predicting future ecosystem condition and climate. Quantifying the θcrit across biomes and climates is challenging because observations of surface energy fluxes and SM remain sparse. Here, we used the latest database of eddy covariance measurements to estimate θcrit across Europe by evaluating evaporative fraction (EF)-SM relationships and investigating the covariance between vapor pressure deficit (VPD) and gross primary production (GPP) during SM dry-down periods. We found that the θcrit and soil matric potential threshold in Europe are 16.5% and −0.7 MPa, respectively. Surface energy partitioning characteristics varied among different vegetation types; EF in savannas had the highest sensitivities to SM in water-limited stage, and the lowest in forests. The sign of the covariance between daily VPD and GPP consistently changed from positive to negative during dry-down across all sites when EF shifted from relatively high to low values. This sign of the covariance changed after longer period of SM decline in forests than in grasslands and savannas. Estimated θcrit from the VPD–GPP covariance method match well with the EF–SM method, showing this covariance method can be used to detect the θcrit. We further found that soil texture dominates the spatial variability of θcrit while shortwave radiation and VPD are the major drivers in determining the spatial pattern of EF sensitivities. Our results highlight for the first time that the sign change of the covariance between daily VPD and GPP can be used as an indicator of how ecosystems transition from energy to SM limitation. We also characterized the corresponding θcrit and its drivers across diverse ecosystems in Europe, an essential variable to improve the representation of water stress in land surface models.
ano.nymous@ccsd.cnrs.fr.invalid (Zheng Fu) 25 Sep 2025
https://hal.science/hal-03502713v1
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[hal-03797527] Structure des couverts forestiers et exposition des forêts et arbres forestiers aux sécheresses : enseignements pour la sylviculture
[...]
ano.nymous@ccsd.cnrs.fr.invalid (Nathalie Bréda) 04 Oct 2022
https://hal.inrae.fr/hal-03797527v1
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[hal-04456551] Comportement des chênes pédonculé et sessile sur deux sols à engorgement temporaire en Lorraine
Dans les années 1970-1980, l'INRA (aujourd'hui INRAE) a installé des plantations expérimentales de chênes sur deux types de sol à nappe temporaire de la Plaine lorraine, en forêts communales de Charmes et Damas-aux-bois (88). Le but initial était de tester différents types d’« assainissement » destinés à améliorer la reprise et la croissance des chênes. Après 4 à 5 décennies, ce dispositif continue de livrer des informations précieuses.
ano.nymous@ccsd.cnrs.fr.invalid (François Lebourgeois) 09 Jul 2024
https://hal.science/hal-04456551v1
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[hal-03468938] CNN-based Method for Segmenting Tree Surface Singularites
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ano.nymous@ccsd.cnrs.fr.invalid (Florian Delconte) 21 May 2025
https://hal.science/hal-03468938v1
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[hal-04054146] Characterizing the calibration domain of remote sensing models using convex hulls
The ever-increasing availability of remote sensing data allows production of forest attributes maps, which are usually made using model-based approaches. These map products are sensitive to various bias sources, including model extrapolation. To identify, over a case study forest, the proportion of extrapolated predictions, we used a convex hull method applied to the auxiliary data space of an airborne laser scanning (ALS) flight. The impact of different sampling efforts was also evaluated. This was done by iteratively thinning a set of 487 systematic plots using nested sub-grids allowing to divide the sample by two at each level. The analysis were conducted for all alternative samples and evaluated against 56 independent validation plots. Residuals of the extrapolated vali-dation plots were computed and examined as a function of their distance to the model calibration domain. Extrapolation was also characterized for the pixels of the area of interest (AOI) to upscale at population level. Results showed that the proportion of extrapolated pixels greatly reduced with an increasing sampling effort. It reached a plateau (ca. 20% extrapolation) with a sampling intensity of ca. 250-calibration plots. This contrasts with results on model's root mean squared error (RMSE), which reached a plateau at a much lower sampling intensity. This result emphasizes the fact that with a low sampling effort, extrapolation risk remains high, even at a relatively low RMSE. For all attributes examined (i.e., stand density, basal area, and quadratic mean diameter) estimations were generally found to be biased for validation plots that were extrapolated. The method allows an easy identification of map pixels that are out of the calibration domain, making it an interesting tool to evaluate model transferability over an area of interest (AOI). It could also serve to compare "competing " models at a variable selection phase. From a model calibration perspective, it could serve a posteriori, to evaluate areas (in the auxiliary space) that merit further sampling efforts to improve model reliability.
ano.nymous@ccsd.cnrs.fr.invalid (Jean-Pierre Renaud) 31 Mar 2023
https://hal.inrae.fr/hal-04054146v1
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[hal-03343133] Drought stress recovery of hydraulic and photochemical processes in Neotropical tree saplings
Climate models predict an increase in the severity and the frequency of droughts. Tropical forests are among the ecosystems that could be highly impacted by these droughts. Here, we explore how hydraulic and photochemical processes respond to drought stress and re-watering. We conducted a pot experiment on saplings of five tree species. Before the onset of drought, we measured a set of hydraulic traits, including minimum leaf conductance, leaf embolism resistance, and turgor loss point. During drought stress, we monitored traits linked to leaf hydraulic functioning (leaf water potential (ψmd) and stomatal conductance (gs)) and traits linked to leaf photochemical functioning (maximum quantum yield of photosystem II (Fv/Fm) and maximum electron transport rate (ETRmax)) at different wilting stages. After re-watering the same traits were measured after 3, 7, and 14 days. Hydraulic trait values decreased faster than photochemical trait values. After re-watering, the values of the four traits recovered at different rates. Fv/Fm recovered very fast close to their initial values only three days after re-watering. This was followed by ETRmax, Ψmd and gs. Finally, we show that species with large stomatal and leaf safety margin and low πtlp are not strongly impacted by drought whereas they have a low recovery on photochemical efficiency. These results demonstrate that πtlp, stomatal and leaf safety margin are a good indicators of plant responses to drought stress and also to recovery for photochemical efficiency.
ano.nymous@ccsd.cnrs.fr.invalid (Olivier Jean Leonce Manzi) 14 Sep 2021
https://hal.inrae.fr/hal-03343133v1
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[hal-03681553] Pit Characters Determine Drought-Induced Embolism Resistance of Leaf Xylem across 18 Neotropical Tree Species
Embolism spreading in xylem is an important component of plant drought resistance. Since embolism resistance has been shown to be mechanistically linked to pit membrane characters in stem xylem, we speculate that similar mechanisms account for leaf xylem. We conducted transmission electron microscopy to investigate pit membrane characters in leaf xylem across 18 Neotropical tree species. We also conducted gold perfusion and polar lipid detection experiments on three species covering the full range of leaf embolism resistance. We then related these observations to previously published data on embolism resistance of leaf xylem. We also incorporated previously published data on stem embolism resistance and stem xylem pit membranes to investigate the link between vulnerability segmentation (i.e., difference in embolism resistance) and leaf-stem anatomical variation. Pit membrane thickness (Tpm,max) and the pit membrane thickness-to-diameter ratio (Tpm,max/Dpm) were predictive of leaf embolism resistance, especially when vestured pits were taken into account. Variation in Tpm,max/Dpm was the only trait predictive of vulnerability segmentation between leaves and stems. Gold particles of 5 and 10 nm infiltrated pit membranes in three species, while the entry of 50-nm particles was blocked. Moreover, polar lipids were associated with inner conduit walls and pits. Our results suggest that mechanisms related to embolism spreading are determined by pit membrane thickness, pore constrictions (i.e., the narrowest bottlenecks along pore pathways), and lipid surfactants, which are largely similar between leaf and stem xylem and between temperate and tropical trees. However, our mechanistic understanding of embolism propagation and the functional relevance of Tpm,max/Dpm remains elusive.
ano.nymous@ccsd.cnrs.fr.invalid (Sébastien Levionnois) 22 Aug 2024
https://hal.inrae.fr/hal-03681553v1
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[hal-03903795] Modeling and propagating inventory‐based sampling uncertainty in the large‐scale forest demographic model “MARGOT”
Models based on national forest inventory (NFI) data intend to project forests under management and policy scenarios. This study aimed at quantifying the influence of NFI sampling uncertainty on parameters and simulations of the demographic model MARGOT. Parameter variance–covariance structure was estimated from bootstrap sampling of NFI field plots. Parameter variances and distributions were further modeled to serve as a plug‐in option to any inventory‐ based initial condition. Forty‐year time series of observed forest growing stock were compared with model simulations to balance model uncertainty and bias. Variance models showed high accuracies. The Gamma distribution best fitted the distributions of transition, mortality and felling rates, while the Gaussian distribution best fitted tree recruitment fluxes. Simulation uncertainty amounted to 12% of the model bias at the country scale. Parameter covariance structure increased simulation uncertainty by 5.5% in this 12%. This uncertainty appraisal allows targeting model bias as a modeling priority.
ano.nymous@ccsd.cnrs.fr.invalid (Timothée Audinot) 16 Dec 2022
https://hal.science/hal-03903795v1
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[hal-03740191] Is Diversification a Suitable Option to Reduce Drought-Induced Risk of Forest Dieback? An Economic Approach Focused on Carbon Accounting
Extreme or recurrent drought events are the principal source of stress on forests, impairing their overall health. They result in financial losses for forest owners and ecosystem service losses for society. Most of the forested area in the Grand-Est region, France, is covered by European beech, which is projected to decline in the future due to repeated drought events driven by climate change. Diversification is a management option that can reduce the drought-induced risk of dieback. Two types of diversification were separately and jointly analyzed: a mixture of beech species with oak species and a mixture of different tree diameter classes. Two types of losses were also considered: financial and in terms of carbon storage under different occurrences of drought events derived from climate change scenarios. We combined an individual-based model of forest growth with a forest economic approach (i.e., land expectation value or LEV), which we adapted to the stochastic context by developing a doubly-weighted LEV. The maximization of the LEV made it possible to identify the most effective adaptation strategies in terms of timber revenue and carbon storage by means of three different carbon values (i.e., market value, shadow price, and social cost). The results showed that diversification increases timber returns and reduces the loss in timber volume due to the drought-induced risk of forest dieback. However, diversification negatively affects carbon storage. Integrating the value of carbon storage increases the value of the forest stand, but only a high carbon value has a significant economic impact.
ano.nymous@ccsd.cnrs.fr.invalid (Sandrine Brèteau-Amores) 10 Jan 2024
https://hal.inrae.fr/hal-03740191v1
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[hal-03694879] Climate change-induced background tree mortality is exacerbated towards the warm limits of the species ranges
Key message : An influence of the recent changes in temperature or rainfall was demonstrated, increasing background tree mortality rates for 2/3 of the 12 studied tree species. Climate change-induced tree mortality was exacerbated towards the warm or dry limits of the species ranges, suggesting in these areas a progressive replacement by more xeric species. Context : Despite the identification of climate change effects on tree mortality in various biomes, the characterization of species-specific areas of vulnerability remains poorly understood. Aims : We sought to assess if the effects of temperature and rainfall changes on background tree mortality rates, which did not result from abrupt disturbances, were linked to climate change intensity only, or if they also depended on the tree’s location along climatic gradients. Methods : We modelled background mortality for 12 of the most common European tree species using 265,056 trees including 4384 dead trees from the French national forest inventory. To explain mortality, we considered variables linked to tree characteristics, stand attributes, logging intensity and site environmental characteristics, and climate change effects. Results : We found an influence of temperature and rainfall changes on 9 species out of 12. For 8 of them, climate change-induced tree mortality was exacerbated towards the warm or dry limits of the species ranges. Conclusion ; These results highlight that tree mortality varies according to the climate change intensity and the tree location along temperature and rainfall gradients. They strengthen the poleward and upward shifts of trees forecasted from climate envelope models for a large number of European tree species.
ano.nymous@ccsd.cnrs.fr.invalid (Adrien Taccoen) 30 Aug 2023
https://hal.science/hal-03694879v1
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[hal-03442289] Ant Colony Optimization for Estimating Pith Position on Images of Tree Log Ends
The pith location is one of the most important features to detect in order to determine the quality of wood. Indeed, it allows to extract other important features. In this paper, we address the problem of pith detection on images of wood cross-sections. Taking such images can be done at little cost and with a high resolution. However, contrary to computed tomographic images, digital images exhibit disturbances like sawing marks, dirt or ambient light variations which make difficult the image analysis. Few studies have focused on such images. Furthermore these studies do some prior segmentation or cropping before the detection. We propose an approach for estimating the pith location without any requirements. Our method is based on an ant colony optimization algorithm. It is a probabilistic approach for solving this task. We validate our algorithm on images of Douglas fir captured after harvesting. The efficiency of this algorithm has been demonstrated by performance comparisons with other approaches. Experiments show an accurate and fast estimation and the algorithm could be used in real time, at sawmill environment or in forest, with a smartphone.
ano.nymous@ccsd.cnrs.fr.invalid (Rémi Decelle) 26 Aug 2024
https://hal.science/hal-03442289v1
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[hal-03647971] Effect of tree demography and flexible root water uptake for modeling the carbon and water cycles of Amazonia
Amazonian forest plays a crucial role in regulating the carbon and water cycles in the global climate system. However, the representation of biogeochemical fluxes and forest structure in dynamic global vegetation models (DGVMs) remains challenging. This situation has considerable implications to simulate the state and dynamics of Amazonian forest. This study aims at simulating the dynamic of the evapotranspiration (ET), productivity (GPP), biomass (AGB) and forest structure of wet tropical forests in the Amazon basin using the updated ORCHIDEE land surface model. The latter is improved for two processes: stand structure and demography, and plant water uptake by roots. Stand structure is simulated by adapting the CAN version of ORCHIDEE, originally developed for temperate forests. Here, we account for the permanent recruitment of young individual trees, the distribution of stand level growth into 20 different cohorts of variable diameter classes, and mortality due to asymmetric competition for light. Plant water uptake is simulated by including soil-to-root hydraulic resistance (RS). To evaluate the effect of the soil resistance alone, we performed factorial simulations with demography only (CAN) and both demography and resistance (CAN-RS). AGB, ET and GPP outputs of CAN-RS are also compared with the standard version of ORCHIDEE (TRUNK) for which eco-hydrological parameters were tuned globally to fit GPP and evapotranspiration at flux tower sites. All the model versions are benchmarked against in situ and regional datasets. We show that CAN-RS correctly reproduce stand level structural variables (as CAN) like diameter classes and tree densities when validated using in-situ data. Besides offering the key advantage to simulate forest's structure, it also correctly simulates ET and GPP and improves fluxes spatial patterns when compared to TRUNK. With the new formulation of soil water uptake, which is driven by soil water availability rather than root-biomass, the simulated trees preferentially use water in the deepest soil layers during the dry seasons. This improves the seasonality of ET and GPP compared to CAN, especially on clay soils for which the soil moisture potential drops rapidly in the dry season. Nevertheless, since demography parameters in CAN-RS are constant for all evergreen tropical forests, spatial variability of AGB and basal area across the Amazon remains too uniform compared to observations, and are very comparable to the TRUNK. Additional processes such as climate driven mortality and phosphorus limitation on growth leading to the prevalence of species with different functional traits across the Amazon need to be included in the future development of this model.
ano.nymous@ccsd.cnrs.fr.invalid (Emilie Joetzjer) 22 Jul 2024
https://hal.inrae.fr/hal-03647971v1
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[hal-03432028] Transferability of an individual- and trait-based forest dynamics model: A test case across the tropics
Individual-based forest models (IBMs) are useful to investigate the effect of environment on forest structure and dynamics, but they are often restricted to site-specific applications. To build confidence for spatially distributed simulations, model transferability, i.e. the ability of the same model to provide reliable predictions at contrasting sites, has to be thoroughly tested. We tested the transferability of a spatially explicit forest IBM, TROLL, with a trait-based species parameterization and global gridded climate forcing, by applying it to two sites with sharply contrasting climate and floristic compositions across the tropics, one in South America and one in Southeast Asia. We identified which parameters are most influential for model calibration and assessed the model sensitivity to climatic conditions for a given calibration. TROLL produced realistic predictions of forest structure and dynamics at both sites and this necessitates the recalibration of only three parameters, namely photosynthesis efficiency, crown allometry and mortality rate. All three relate to key processes that constrain model transferability and warrant further model development and data acquisition, with mortality being a particular priority of improvement for the current generation of vegetation models. Varying the climatic conditions at both sites demonstrate similar, and expected, model responses: GPP increased with temperature and irradiance, while stem density and aboveground biomass declined as temperature increased. The climate dependence of productivity and biomass was mediated by plant respiration, carbon allocation and mortality, which has implications both on model development and on forecasting of future carbon dynamics. Our detailed examination of forest IBM transferability unveils key processes that need to improve in genericity before reliable large-scale implementations can be envisioned.
ano.nymous@ccsd.cnrs.fr.invalid (E-Ping Rau) 05 Jan 2024
https://hal.inrae.fr/hal-03432028v1
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[hal-03821890] Developing semantic interoperability in ecosystem studies: semantic modelling and annotation for FAIR data production
The study of ecosystem characteristics and functioning requires multidisciplinary approaches and mobilises multiple research teams. Data are collected or computed in large quantity but are most often poorly standardised and therefore heterogeneous. In this context the development of semantic interoperability is a major challenge for the sharing and reuse of these data. This objective is implemented within the framework of the AnaEE (Analysis and Experimentation on Ecosystems) Research Infrastructure dedicated to experimentation on ecosystems and biodiversity. A distributed Information System (IS) is developed, based on the semantic interoperability of its components using common vocabularies (AnaeeThes thesaurus and OBOE-based ontology extended for disciplinary needs) for modelling observations and their experimental context. The modelling covers the measured variables, the different components of the experimental context, from sensor and plot to network. It consists in the atomic decomposition of the observations, identifying the observed entities, their characteristics and qualification, naming standards and measurement units. This modelling allows the semantic annotation of relational databases and flat files for the production of graph databases. A first pipeline is developed for the automation of the annotation process and the production of the semantic data, annotation that may represent a huge conceptual and practical work without such automation. A second pipeline is devoted to the exploitation of these semantic data through the generation i) of standardized GeoDCAT and ISO metadata records and ii) of data files (NetCDF format) from selected perimeters (experimental sites, years, experimental factors, measured variables...). Carried out on all the data generated by the experimental platforms, this practice will produce semantically interoperable data that meets the linked opendata standards. The work carried out contributes to the development and use of semantic vocabularies within the ecology research community. The genericity of the tools make them usable in different contexts of ontologies and databases.
ano.nymous@ccsd.cnrs.fr.invalid (Christian Pichot) 20 Oct 2022
https://cnrs.hal.science/hal-03821890v1
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[hal-04214883] Towards the homogeneization of leaf senescence observations through reference colour charts based on Munsell coulours and physiological measurements
The vegetative season length plays an important role in the annual carbon production of plants. It is determined by both the bud burst date and the leaf senescence date. Whereas the budburst is an event easily observable (a binary observation indicating if the bud is burst or not), the leaf decolouration is more subjective due to the progressive and long aspect of the process. The observation of the beginning of colour changing can be more or less late (from light green to yellow) according to the observers that could lead to a false shift of observations among the observers (Liu et al, 2021). Our objective is to develop tools to homogenise these observations.In the working group of the TEMPO network (https://tempo.pheno.fr/soere-tempo_eng/) on the leaf senescence, during two vegetative seasons (from the end of leaf expansion to the end of leaf fall), leaves were collected monthly in summer and weekly or biweekly during autumn in shaded and sunned canopy positions, on different tree species including forest (Fagus sylvatica, Quercus robur, Quercus petraea, Carpinus betulus and poplar hybrid (Populus deltoides × Populus nigra)) and fruit (Malus domestica and Prunus avium) species and in different locations in France for some species. The colour of theses leaves was immediately measured thanks to a PANTONE CAPSURE™ including the complete Munsell® colour chart. The leaf chlorophyll content was also estimated with a chlorophyll meter on the same leaves. From the combination of the colour measurements in the different locations or years, a reference colours chart has been identified for each species. This chart combines i) the main summer reference colours which could be different among trees within a same species according to the growing conditions of trees; ii) the colour when leaf senescence starts that we have defined as the colour from which leaves have lost 50% of their chlorophyll content and iii) the main colours during the leaf senescence.The perspective of the project is to extend this approach for a large number of species to build a standard tool to measure the leaf senescence in trees and even beyond in all perennial plants in various ecological context. For example, the development of these reference colour charts could help to homogenise the leaf senescence observations in professional networks (ex: RENECOFOR for forest species in France) or in citizen sciences projects (ex: observatoire des saisons).
ano.nymous@ccsd.cnrs.fr.invalid (Catherine Massonnet) 22 Sep 2023
https://hal.science/hal-04214883v1
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[hal-03880254] The 2018 European heatwave led to stem dehydration but not to consistent growth reductions in forests
Abstract Heatwaves exert disproportionately strong and sometimes irreversible impacts on forest ecosystems. These impacts remain poorly understood at the tree and species level and across large spatial scales. Here, we investigate the effects of the record-breaking 2018 European heatwave on tree growth and tree water status using a collection of high-temporal resolution dendrometer data from 21 species across 53 sites. Relative to the two preceding years, annual stem growth was not consistently reduced by the 2018 heatwave but stems experienced twice the temporary shrinkage due to depletion of water reserves. Conifer species were less capable of rehydrating overnight than broadleaves across gradients of soil and atmospheric drought, suggesting less resilience toward transient stress. In particular, Norway spruce and Scots pine experienced extensive stem dehydration. Our high-resolution dendrometer network was suitable to disentangle the effects of a severe heatwave on tree growth and desiccation at large-spatial scales in situ, and provided insights on which species may be more vulnerable to climate extremes.
ano.nymous@ccsd.cnrs.fr.invalid (Roberto Salomón) 01 Dec 2022
https://agroparistech.hal.science/hal-03880254v1
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[hal-04753421] Seguimiento de la tasa de mortalidad de los árboles en un bosque tropical húmedo mediante LiDAR aéreo multitemporal empleando software libre.
La medición de las tasas de mortalidad de los árboles es crucial para reducción de las incertidumbres en la contribución de los bosques tropicales a la captación del carbono, permitiéndonos también mejorar nuestra compresión de los escenarios y posibles efectos del cambio climático sobre los bosques tropicales. En este estudio se pretende evaluar el potencial del escaneo LiDAR aéreo repetido ALS (escaneo láser aerotransportado) para cartografiar la estructura de los bosques en grandes áreas, con una gran precisión para detectar patrones de mortalidad a nivel de paisaje, empleando para el procesamiento software libre como R , específicamente sus librerias lidR (Roussel and Auty, 2020) y raster, así como el software QGIS para las salidas y mapas de presentación de la mortalidad. Este estudio contribuye a nuestra comprensión de los patrones espaciales y temporales de la mortalidad a escala del paisaje. Igualmente, brinda una herramienta y una metodología precisa y reproductible para poder obtener mapas de mortalidad empleando tecnología geoespacial libre. Este tipo de procesos nos permiten a nivel global identificar las limitaciones y generar las recomendaciones para extrapolar esta información a zonas más amplias, apoyando la medición precisa del importe de carbono, así como orientando las acciones políticas y de conservación en zonas vulnerables o en riesgo por el cambio climático
ano.nymous@ccsd.cnrs.fr.invalid (Claudia Milena Huertas Garcia) 25 Oct 2024
https://hal.inrae.fr/hal-04753421v1
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[hal-03890685] Contrasting drought-response strategies and vulnerability to hydraulic failure in saplings of rainforest tree species
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ano.nymous@ccsd.cnrs.fr.invalid (Camille Ziegler) 08 Dec 2022
https://hal.science/hal-03890685v1
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[hal-05167356] Réseau ESPERENSE : une évaluation participative des essences de demain
Le projet ESPERENSE est achevé, vive le réseau ESPERENSE ! Un réseau de sites expérimentaux répondant à la stratégie et aux principes définis dans le projet mais aussi une communauté d’expérimentateurs très investis, chacun à son niveau, de la recherche à la gestion forestière…
ano.nymous@ccsd.cnrs.fr.invalid (Eric Paillassa) 17 Jul 2025
https://hal.science/hal-05167356v1
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[hal-04476089] Of sensors and intercalibrations: The need for standardized protocols and consequences on microclimate studies relying on low-cost temperature sensors
The use of temperature sensors in ecology has grown rapidly, due to the increasing accessibility to low-cost and miniaturized versions. We usually rely on a network of sensors to accurately assess temperature variability near the ground at fine spatiotemporal resolutions. As the distance among neighbouring sensors decreases, the observed spatial variation in temperatures gets closer to their measurement uncertainty. This can have important consequences if such differences are instead interpreted as local microclimatic effects. Hence, it is of utmost importance to use relevant metrological and statistical procedures, to account for this potential bias before analysing microclimatic data. Here, we present a simple and generalizable intercalibration protocol that does not require ultrafine-wire thermocouples of research-grade accuracy for assessing the reference temperature. We applied our protocol on a set of temperature loggers typically used by ecologists: HOBO Pendant, ONSET (n = 376) and TMS, TOMST (n = 122). Each miniature data logger was installed on a regular grid in a climatic chamber, covering a temperature range of 5 to 30°C. The reference temperature in the chamber was assessed by using a spatial analysis based on the position of each data logger inside the grid, in order to account for potential spatial autocorrelation. We then derived an offset (interpolated reference temperature – sensor temperature) for each sensor based on its position on the grid, which provides an estimate of the uncertainty of each temperature sensor. Finally, we used the estimated uncertainty values to assess the effect of this inter-calibration procedure on subsequent in-situ forest microclimate measurements, from the same set of intercalibrated sensors. Our protocol aims at filling a gap in how ecologists currently handle microclimatic data from low-costs temperature loggers, with a need to account for metrological issues and how this may impact the subsequent analysis of microclimatic data in ecology.
ano.nymous@ccsd.cnrs.fr.invalid (Fabien Spicher) 24 Feb 2024
https://hal.science/hal-04476089v1
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[mnhn-03945780] Multi-element composition and isotopic signatures of strontium and neodymium in charred wood and their potential for provenance studies
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ano.nymous@ccsd.cnrs.fr.invalid (Anna Imbert Stulc) 18 Jan 2023
https://mnhn.hal.science/mnhn-03945780v1
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[hal-03643415] A limited number of species is sufficient to assign a vegetation plot to a forest vegetation unit
Aims: Inventorying the habitats composing Natura 2000 sites is mandatory in the European Union and is necessary to implement relevant conservation measures. Vegetation plots, recording the presence or abundance of all plant species co-occurring within a plot, are currently used to identify terrestrial Natura 2000 habitat types, whose descriptions are mainly based on phytosociological units. However, vegetation plots are time-consuming and frequently restricted to the growing season. Moreover, no vegetation plots can be regarded as exhaustive, and significant inter-observer variation has been highlighted. We studied whether reducing the number of recorded species and the time spent carrying out a vegetation plot had an impact on vegetation unit assignment using species presence. We also studied if vegetation plots recorded in winter could be used for vegetation unit assignment. Location: Mainland France. Methods: We used 273 vegetation plots covering French temperate and mountainous forests. The time at which species were sighted was recorded. We also estimated whether a species was recognisable in winter. We used a classification program to compare assignments based on complete and incomplete vegetation plots. Results: Ten species and five minutes were sufficient to assign a plot to an association, and to an alliance, seven species and four minutes. Vegetation unit assignment proved feasible in winter, especially at the alliance level. Conclusions: We confirmed that a limited number of species is sufficient to assign vegetation plots to vegetation units. However, mapping habitats requires habitat identification and delimitation. This study confirms current field habits, particularly when creating a habitat map, usually based on a limited number of recorded species. Lastly, it confirms that the use of vegetation plots coming from a great variety of sources is relevant to create habitat time series, crucial tools for monitoring habitats at a national scale.
ano.nymous@ccsd.cnrs.fr.invalid (Lise Maciejewski) 15 Apr 2022
https://hal.science/hal-03643415v1
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[hal-03860136] Plant root growth against a mechanical obstacle: the early growth response of a maize root facing an axial resistance is consistent with the Lockhart model
Plant root growth is dramatically reduced in compacted soils, affecting the growth of the whole plant. Through a model experiment coupling force and kinematics measurements, we probed the force–growth relationship of a primary root contacting a stiff resisting obstacle, which mimics the strongest soil impedance variation encountered by a growing root. The growth of maize roots just emerging from a corseting agarose gel and contacting a force sensor (acting as an obstacle) was monitored by time-lapse imaging simultaneously to the force. The evolution of the velocity field along the root was obtained from kinematics analysis of the root texture with a particle image velocimetry derived technique. A triangular fit was introduced to retrieve the elemental elongation rate or strain rate. A parameter-free model based on the Lockhart law quantitatively predicts how the force at the obstacle modifies several features of the growth distribution (length of the growth zone, maximal elemental elongation rate and velocity) during the first 10 min. These results suggest a strong similarity of the early growth responses elicited either by a directional stress (contact) or by an isotropic perturbation (hyperosmotic bath).
ano.nymous@ccsd.cnrs.fr.invalid (Manon Quiros) 18 Nov 2022
https://hal.science/hal-03860136v1
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[hal-03736228] Non-structural carbohydrates and morphological traits of leaves, stems and roots from tree species in different climates
Objectives: Carbon fixed during photosynthesis is exported from leaves towards sink organs as non-structural carbohydrates (NSC), that are a key energy source for metabolic processes in trees. In xylem, NSC are mostly stored as soluble sugars and starch in radial and axial parenchyma. The multi-functional nature of xylem means that cells possess several functions, including water transport, storage and mechanical support. Little is known about how NSC impacts xylem multi-functionality, nor how NSC vary among species and climates. We collected leaves, stem and root xylem from tree species growing in three climates and estimated NSC in each organ. We also measured xylem traits linked to hydraulic and mechanical functioning. Data description: The paper describes functional traits in leaves, stems and roots, including NSC, carbon, nitrogen, specific leaf area, stem and root wood density and xylem traits. Data are provided for up to 90 angiosperm species from temperate, Mediterranean and tropical climates. These data are useful for understanding the trade-offs in resource allocation from a whole-plant perspective, and to better quantify xylem structure and function related to water transportation, mechanical support and storage. Data will also give researchers keys to understanding the ability of trees to adjust to a changing climate.
ano.nymous@ccsd.cnrs.fr.invalid (Guangqi Zhang) 22 Jul 2022
https://hal.inrae.fr/hal-03736228v1
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[hal-04019710] Provenance Differences in Water-Use Efficiency Among Sessile Oak Populations Grown in a Mesic Common Garden
Context As a widespread species, sessile oak ( Quercus petraea ) populations occupy a wide range of ecological conditions, with large gradients of soil water availability. Drought acclimation involves a plastic increase in water-use efficiency (WUE), a trait that is easily measured using the carbon isotope composition (δ 13 C). However, the question remains whether WUE is an adaptive trait that impacts the fitness of trees in natural environments. Objectives and Methods To investigate whether WUE was a drought-adaptive trait, we studied a sample of 600 trees originating from 16 provenances, grown for 21 years in a common garden. Intrinsic WUE (WUE i ), estimated from tree ring δ 13 C, was compared among and within populations for three climatically contrasted years. The adaptive character of WUE i was evaluated by relating population mean WUE i , as well as its plasticity to drought, to the pedoclimatic conditions of their provenance sites. The contribution of WUE i to tree and population fitness was finally assessed from the relationship between WUE i and tree radial growth (GI). Results Significant differences in WUE i were found among populations but a much larger variability was observed within than among populations. The population WUE i of the juvenile oak trees growing in the relatively mesic conditions of the common garden showed no relationship with a modeled water deficit index for the provenance sites. However, a higher population WUE i plasticity to severe drought was related to a higher proportion of silt and carbon and a lower proportion of sand in the soil of the provenance sites. In response to severe drought, populations with a higher increase in WUE i showed a lower decrease in GI. Populations with lower GI reduction were from sites with higher vapor pressure deficit in May–July (VPD). For the wet year only, populations with a higher WUE i also had a higher GI. Conclusion The correlations observed at the common garden site between (i) population means of WUE i plasticity to drought and soil texture of the provenance sites, and (ii) GI plasticity to drought and VPD, suggested a local adaptation of sessile oak.
ano.nymous@ccsd.cnrs.fr.invalid (Arivoara Rabarijaona) 13 Mar 2023
https://hal.inrae.fr/hal-04019710v1
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[hal-03798816] Deuterium oxide elimination kinetics for estimation of body water mass and flux: Developments for a thrifty, rapid and noninvasive method in dairy goats
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ano.nymous@ccsd.cnrs.fr.invalid (L. Louis) 05 Oct 2022
https://hal.inrae.fr/hal-03798816v1
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[hal-03721086] Water table depth modulates productivity and biomass across Amazonian forests
Aim: Water availability is the major driver of tropical forest structure and dynamics. Most research has focused on the impacts of climatic water availability, whereas remarkably little is known about the influence of water table depth and excess soil water on forest processes. Nevertheless, given that plants take up water from the soil, the impacts of climatic water supply on plants are likely to be modulated by soil water conditions. Location: Lowland Amazonian forests. Time period: 1971–2019. Methods: We used 344 long-term inventory plots distributed across Amazonia to analyse the effects of long-term climatic and edaphic water supply on forest functioning. We modelled forest structure and dynamics as a function of climatic, soil-water and edaphic properties. Results: Water supplied by both precipitation and groundwater affects forest structure and dynamics, but in different ways. Forests with a shallow water table (depth &lt;5 m) had 18% less above-ground woody productivity and 23% less biomass stock than forests with a deep water table. Forests in drier climates (maximum cumulative water deficit &lt; −160 mm) had 21% less productivity and 24% less biomass than those in wetter climates. Productivity was affected by the interaction between climatic water deficit and water table depth. On average, in drier climates the forests with a shallow water table had lower productivity than those with a deep water table, with this difference decreasing within wet climates, where lower productivity was confined to a very shallow water table. Main conclusions: We show that the two extremes of water availability (excess and deficit) both reduce productivity in Amazon upland (terra-firme) forests. Biomass and productivity across Amazonia respond not simply to regional climate, but rather to its interaction with water table conditions, exhibiting high local differentiation. Our study disentangles the relative contribution of those factors, helping to improve understanding of the functioning of tropical ecosystems and how they are likely to respond to climate change.
ano.nymous@ccsd.cnrs.fr.invalid (Thaiane Sousa) 17 Aug 2024
https://hal.inrae.fr/hal-03721086v1
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[hal-04223378] Renouvellement des peuplements forestiers en contexte de changement global : opportunités et difficultés
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ano.nymous@ccsd.cnrs.fr.invalid (Catherine C. Collet) 29 Sep 2023
https://hal.inrae.fr/hal-04223378v1
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[hal-03699094] Satellite Imagery to Map Topsoil Organic Carbon Content over Cultivated Areas: An Overview
There is a need to update soil maps and monitor soil organic carbon (SOC) in the upper horizons or plough layer for enabling decision support and land management, while complying with several policies, especially those favoring soil carbon storage. This review paper is dedicated to the satellite-based spectral approaches for SOC assessment that have been achieved from several satellite sensors, study scales and geographical contexts in the past decade. Most approaches relying on pure spectral models have been carried out since 2019 and have dealt with temperate croplands in Europe, China and North America at the scale of small regions, of some hundreds of km2: dry combustion and wet oxidation were the analytical determination methods used for 50% and 35% of the satellite-derived SOC studies, for which measured topsoil SOC contents mainly referred to mineral soils, typically cambisols and luvisols and to a lesser extent, regosols, leptosols, stagnosols and chernozems, with annual cropping systems with a SOC value of ~15 g·kg−1 and a range of 30 g·kg−1 in median. Most satellite-derived SOC spectral prediction models used limited preprocessing and were based on bare soil pixel retrieval after Normalized Difference Vegetation Index (NDVI) thresholding. About one third of these models used partial least squares regression (PLSR), while another third used random forest (RF), and the remaining included machine learning methods such as support vector machine (SVM). We did not find any studies either on deep learning methods or on all-performance evaluations and uncertainty analysis of spatial model predictions. Nevertheless, the literature examined here identifies satellite-based spectral information, especially derived under bare soil conditions, as an interesting approach that deserves further investigations. Future research includes considering the simultaneous analysis of imagery acquired at several dates i.e., temporal mosaicking, testing the influence of possible disturbing factors and mitigating their effects fusing mixed models incorporating non-spectral ancillary information.
ano.nymous@ccsd.cnrs.fr.invalid (Emmanuelle Vaudour) 19 Jul 2024
https://hal.inrae.fr/hal-03699094v1
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[hal-03905771] Plants from Season to Season: a phenological observation guidebook
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ano.nymous@ccsd.cnrs.fr.invalid (Vincent V. Badeau) 19 Dec 2022
https://hal.inrae.fr/hal-03905771v1
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[hal-03693215] Apport d'un nouveau protocole de régionalisation dynamique du climat pour l'estimation du bilan hydrique de douglasaies
La quantification des impacts régionalisés du changement climatique sur les forêts est un enjeu majeur, tant écologique que socio-économique. Le dépérissement des douglasaies (Pseudotsuga menziesii) est observé depuis une vingtaine d'années et pourrait s'accélérer. Des travaux récents montrent que l'estimation régionalisée du bilan hydrique sous couvert forestier se heurte à la capacité des modèles climatiques régionaux à simuler correctement la quantité et le cycle saisonnier des précipitations. Nous évaluons ici la capacité d'un nouveau protocole de régionalisation du climat à simuler un régime de précipitations réaliste nécessaire au calcul de bilan hydrique forestier.
ano.nymous@ccsd.cnrs.fr.invalid (Valentin Blanchet) 10 Jun 2022
https://institut-agro-dijon.hal.science/hal-03693215v1
