2022 - UMR Silva

[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

[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

[hal-03543468] Sphagnum physiological responses to elevated temperature, nitrogen, CO2 and low moisture in laboratory and in situ microhabitats: a review

Sphagnum mosses are considered peatland engineers because of their ability to create conditions inducing carbon accumulation. Here, we report on a review of the effects of four environmental variables (elevated temperature, N and CO2 and reduced moisture) on the capitulum biomass, length increment, respiration, photosynthetic capability, N and P exchange and content of the 3 most studied Sphagnum subgenera (Acutifolia, Cuspidata, Sphagnum). Overall, we observe that, when compared to in situ experiments, laboratory experiments tend to exacerbate length increments and underestimate maximum photosynthesis in most of the studies inventoried. This review underscores some differences among results that can be associated with the used of different protocols (e.g. exposure time, instrumental analysis). Studies that investigated the impact of elevated temperature (2-5 degrees C) on Sphagnum reveal an increase in length, respiration and photosynthesis regardless of the experimental conditions and subgenus. Elevated N (3-23 g Nm(-2)y(-1)) on the other hand appears to reduce the length increment but had contrasting effects on photosynthesis. Some divergent responses are found with Cuspidata species because of their tolerance to high doses of N. Low moisture reduces the length increment and photosynthesis of species of the Cuspidata and Sphagnum subgenera but has different effects on species of the Acutifolia subgenus, which are relatively tolerant to water fluctuations. Responses to elevated CO2 have no clear trends reported. Allelochemical interactions between Sphagnum, their microbiome or surrounding mosses or other plants were found to be determinant to Sphagnum responses under those variables and reinforce the interest of such investigations.

ano.nymous@ccsd.cnrs.fr.invalid (Geneviève Chiapusio) 26 Jan 2022

https://hal.inrae.fr/hal-03543468v1

[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

[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

[hal-03926054] Identification and spatial extent of understory plant species requiring vegetation control to ensure tree regeneration in French forests

Abstract Key message Fifteen species are most susceptible to require vegetation control during tree regeneration in the range of our study. Among these 15 species, Rubus fruticosus , Pteridium aquilinum , and Molinia caerulea cover each more than 300,000 ha of open-canopy forests. Context Vegetation control, i.e., the reduction of competitive species cover, is often required to promote tree seedling establishment during the forest regeneration stage. The necessity to control understory vegetation largely depends on the species to be controlled. In order to plan forest renewal operations, it is critical to identify which species require vegetation control during the regeneration stage and to quantify the forest area affected by these species. Aims We aimed at identifying the main species requiring vegetation control and at estimating the forest area they cover at the national level. Methods Using National Forest Inventory data, we created four indicators based on two levels of plant cover, cross-referenced with two levels of canopy opening, and compared them to the outcome of a survey of forest manager practices. Results The best indicator was the one that represented the proportion of forests with open canopy where the species was present with a large cover in the understory. In non-Mediterranean France, according to the indicator, a total of 15 species were found to frequently require vegetation control during the tree regeneration stage. Pteridium aquilinum , Molinia caerulea , and Rubus fruticosus were the main species, and each covered more than 300,000 ha of forest with open canopies, representing about 13% of the total forest area with open canopies outside of the Mediterranean area. Conclusions Forests covered by species requiring vegetation control according to forest managers represent a large share of the forest area undergoing regeneration. This study provides the first list of species that require vegetation control based on a methodological protocol that makes it possible to calculate the area associated with each species.

ano.nymous@ccsd.cnrs.fr.invalid (Noé Dumas) 02 Feb 2023

https://hal.science/hal-03926054v1

[hal-03468938] CNN-based Method for Segmenting Tree Surface Singularites

[...]

ano.nymous@ccsd.cnrs.fr.invalid (Florian Delconte) 07 Dec 2021

https://hal.science/hal-03468938v1

[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

[hal-03768111] Multisource forest inventories: A model-based approach using k-NN to reconcile forest attributes statistics and map products

Forest map products are widely used and have taken benefit from progresses in the multisource forest inventory approaches, which are meant to improve the precision of forest inventory estimates at high spatial resolution. However, estimating errors of pixel-wise predictions remains difficult, and reconciling statistical outcomes with map products is still an open and important question. We address this problem using an original approach relying on a model-based inference framework and k-nearest neighbours (k-NN) models to produce pixel-wise estimations and related quality assessment. Our approach takes advantage of the resampling properties of a model-based estimator and combines it with geometrical convex-hull models to measure respectively the precision and accuracy of pixel predictions. A measure of pixel reliability was obtained by combining precision and accuracy. The study was carried out over a 7,694 km2 area dominated by structurally complex broadleaved forests in centre of France. The targeted forest attributes were growing stock volume, basal area and growing stock volume increment. A total of 819 national forest inventory plots were combined with auxiliary data extracted from a forest map, Landsat 8 images, and 3D point clouds from both airborne laser scanning and digital aerial photogrammetry. k-NN models were built independently for both 3D data sources. Both selected models included 5 auxiliary variables, and were generated using 5 neighbours, and most similar neighbours distance measure. The models showed relative root mean square error ranging from 35.7% (basal area, digital aerial photogrammetry) in calibration to 63.4% (growing stock volume increment, airborne laser scanning) in the validation set. At pixel level, we found that a minimum of 86.4% of the predictions were of high precision as their bootstrapped coefficient of variation fall below calibration’s relative root mean square error. The amount of extrapolation varied from 4.3% (digital aerial photogrammetry) to 6.3% (airborne laser scanning). A relationship was found between extrapolation and k-NN distance, opening new opportunities to correct extrapolation errors. At the population level, airborne laser scanning and digital aerial photogrammetry performed similarly, offering the possibility to use digital aerial photogrammetry for monitoring purposes. The proposed method provided consistent estimates of forest attributes and maps, and also provided spatially explicit information about pixel predictions in terms of precision, accuracy and reliability. The method therefore produced high resolution outputs, significant for either decision making or forest management purposes.

ano.nymous@ccsd.cnrs.fr.invalid (Ankit Sagar) 30 Aug 2023

https://hal.science/hal-03768111v1

[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

[hal-03518448] Tropical and subtropical Asia's valued tree species under threat

Tree diversity in Asia’s tropical and subtropical forests is central to nature-based solutions. Species vulnerability to multiple threats, which affectstheprovision of ecosystem services,is poorly understood. We conducteda region-wide, spatially explicit vulnerability assessment(including overexploitation, fire, overgrazing, habitat conversion, andclimate change) of63socio-economically important tree speciesselected from national priority lists and validated by anexpert network representing20 countries. Overall, 74% of the most important areas for conservation of these trees fall outside of protected areas, with species severelythreatened across 47% of their native ranges. The most imminent threats areoverexploitation and habitat conversion, with populations being severely threatened in an average of 24% and 16% of their distribution areas. Optimistically, our results predict relativelylimited overall climate change impacts, however, some of thestudy species arelikelyto lose more than 15% of their habitat by 2050 because of climate change. We pinpoint specific natural forest areas in Malaysia and Indonesia(Borneo) as hotspots for on-site conservationof forest genetic resources, more than 82% of which do not currently fall within designated protected areas. We also identify degraded lands in Indonesia (Sumatra) as priorities for restoration where planting or assisted natural regeneration will help maintain these species into the future, while croplands in Southern India are highlighted as potentially important agroforestry options.Our study highlights the need for regionally coordinated action for effective conservation and restoration.

ano.nymous@ccsd.cnrs.fr.invalid (Hannes Gaisberger) 09 Jan 2022

https://hal.science/hal-03518448v1

[hal-03880260] Regional climate moderately influences species-mixing effect on tree growth-climate relationships and drought resistance for beech and pine across Europe

Increasing species diversity is considered a promising strategy to mitigate the negative impacts of global change on forests. However, the interactions between regional climate conditions and species-mixing effects on climate-growth relationships and drought resistance remain poorly documented. In this study, we investigated the patterns of species-mixing effects over a large gradient of environmental conditions throughout Europe for European beech (Fagus sylvatica L.) and Scots pine (Pinus sylvestris L.), two species with contrasted ecological traits. We hypothesized that across large geographical scales, the difference of climate-growth relationships and drought resistance between pure and mixed stands would be dependent on regional climate. We used tree ring chronologies derived from 1143 beech and 1164 pine trees sampled in 30 study sites, each composed of one mixed stand of beech and pine and of the two corresponding pure stands located in similar site conditions. For each site and stand, we used Bootstrapped Correlation Coefficients (BCCs) on standardized chronologies and growth reduction during drought years on raw chronologies to analyze the difference in climate-tree growth relationships and resistance to drought between pure and mixed stands. We found consistent large-scale spatial patterns of climate-growth relationships. Those patterns were similar for both species. With the exception of the driest climates where pure and mixed beech stands tended to display differences in growth correlation with the main climatic drivers, the mixing effects on the BCCs were highly variable, resulting in the lack of a coherent response to mixing. No consistent species-mixing effect on drought resistance was found within and across climate zones. On average, mixing had no significant effect on drought resistance for neither species, yet it increased pine resistance in sites with higher climatic water balance in autumn. Also, beech and pine most often differed in the timing of their drought response within similar sites, irrespective of the regional climate, which might increase the temporal stability of growth in mixed compared to pure stands. Our results showed that the impact of species mixing on tree response to climate did not strongly differ between groups of sites with distinct climate characteristics and climate-growth relationships, indicating the interacting influences of species identity, stand characteristics, drought events characteristics as well as local site conditions.

ano.nymous@ccsd.cnrs.fr.invalid (Géraud de Streel) 14 Dec 2022

https://agroparistech.hal.science/hal-03880260v1

[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

[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

[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

[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) 06 Dec 2023

https://hal.inrae.fr/hal-04327109v1

[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 &gt;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

[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

[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

[hal-04226870] The 2018 hot drought pushed conifer wood formation to the limit of its plasticity : Consequences for woody biomass production and tree ring structure

Hot droughts are expected to increase in Europe and disturb forest ecosystem functioning. Wood formation of trees has the potential to adapt to those events by compensatory mechanisms between the rates and durations of tracheid differentiation to form the typical pattern of vital wood anatomical structures. We monitored xylogenesis and measured wood anatomy of mature silver fir ( Abies alba Mill.) and Scots pine ( Pinus sylvestris L.) trees along an elevational gradient in the Black Forest during the hot drought year of 2018. We assessed the kinetics of tracheid differentiation and the final tracheid dimensions and quantified the relationship between rates and durations of cell differentiation over the growing season. Cell differentiation kinetics were decoupled, and temperature and water availability signals were imprinted in the tree ring structure. The sudden decline in woody biomass production provided evidence for a disruption in carbon sequestration processes due to heat and drought stress. Growth processes of Scots pine (pioneer species) were mainly affected by the spring drought, whereas silver fir (climax species) growth processes were more disturbed by the summer drought. Our study provides novel insights on the plasticity of wood formation and carbon allocation in temperate conifer tree species in response to extreme climatic events.

ano.nymous@ccsd.cnrs.fr.invalid (E. Larysch) 03 Oct 2023

https://hal.inrae.fr/hal-04226870v1

[hal-04226892] Wood Formation Modeling – A Research Review and Future Perspectives

Wood formation has received considerable attention across various research fields as a key process to model. Historical and contemporary models of wood formation from various disciplines have encapsulated hypotheses such as the influence of external (e.g., climatic) or internal (e.g., hormonal) factors on the successive stages of wood cell differentiation. This review covers 17 wood formation models from three different disciplines, the earliest from 1968 and the latest from 2020. The described processes, as well as their external and internal drivers and their level of complexity, are discussed. This work is the first systematic cataloging, characterization, and process-focused review of wood formation models. Remaining open questions concerning wood formation processes are identified, and relate to: (1) the extent of hormonal influence on the final tree ring structure; (2) the mechanism underlying the transition from earlywood to latewood in extratropical regions; and (3) the extent to which carbon plays a role as “active” driver or “passive” substrate for growth. We conclude by arguing that wood formation models remain to be fully exploited, with the potential to contribute to studies concerning individual tree carbon sequestration-storage dynamics and regional to global carbon sequestration dynamics in terrestrial vegetation models.

ano.nymous@ccsd.cnrs.fr.invalid (Annemarie H Eckes-Shephard) 03 Oct 2023

https://hal.inrae.fr/hal-04226892v1

[hal-03888147] No matter how much space and light are available, radial growth distribution in Fagus sylvatica L. trees is under strong biomechanical control

Key message This study presents the first attempt to quantify how the thigmomorphogenetic syndrome is involved in Fagus sylvatica L. tree growth responses to thinning. An experimental design preventing mechanosensing in half of the trees demonstrated that radial growth distribution in roots and along the tree stem is under strong biomechanical control. Context Studies on the mechanosensitive control of growth under real forest conditions are rare and those existing to date all deal with conifer species. In the current context of global changes, it is important to disentangle how different biotic and abiotic factors affect tree growth. Aims Whereas growth changes after thinning are usually interpreted as responses to decreased competition for resources, this study investigates the importance of how mechanosensing controls growth distribution inside the tree. Methods In an even-aged beech stand, 40 pole-sized trees (size class at first thinning) were selected, half of the plot was thinned and, within each sub-plot (thinned and unthinned), half of the tree were guy-wired in order to remove mechanical stimulations to the lower part of the stem. Four years later, all trees were felled and volume increment, ring width distribution along the tree height, and the largest ring width of the structural roots were measured. The effect of mechanical stimulation in the two treatments (thinned and unthinned) was assessed. Results Removal of mechanical stimulation decreased the volume increment in the lower part of the stem as well as radial root growth but did not affect axial growth. When mechanical strain was removed, the ring width distribution along the stem height changed drastically to an ice-cream cone-like distribution, indicating a strong mechanosensitive control of tree shape. Conclusion In a forest stand, the growth allocation inside the tree is under strong mechanical control. Mechanical stimulations explain more than 50% of the increment stimulated by thinning, whatever the growth indicator. A further challenge is to better understand how cambial cells perceive strains during growth in order to integrate mechanosensing into process-based tree-growth modeling.

ano.nymous@ccsd.cnrs.fr.invalid (Joel Hans Dongmo Keumo Jiazet) 07 Dec 2022

https://agroparistech.hal.science/hal-03888147v1

[hal-03926051] Beech and hornbeam dominate oak 20 years after the creation of storm-induced gaps

Oak (Quercus petraea (Matt.) Liebl. and Quercus robur L. grouped), European beech (Fagus sylvatica L.) and hornbeam (Carpinus betulus L.) are three major species of western and central European forests. When conditions are suitable for the three species, silvicultural management often favours oak because of its greater economic interest. Forest managers know that beech and hornbeam are strong competitors for oak during the regeneration phase, but the conditions that influence the relative success of the regeneration of the three species growing in mixture are still poorly characterised. The natural regeneration of the three species 20 years after canopy openings was studied based on 108 study sites established in 2001 in French forests impacted by the windstorms Lothar and Martin in 1999. In spring and summer 2018 and 2019, all saplings over 0.1 m in height were counted, species were identified and diameter at breast height (DBH) was measured for all saplings over 1.30 m. The height of the saplings with the highest and median DBH in each plot was recorded for each species. Mixed models were used to analyse the combined effects of former stand type, distance from the edge of the gap and soil conditions on species presence, sapling abundance, DBH and height. The modelling approach highlighted the preponderant role of the initial seed rain on the presence and sapling density of the three species compared to interspecific competition or distance from the edge. The two latter factors had a secondary effect on sapling DBH and height. Beech and hornbeam saplings were more abundant than oak saplings regardless of soil conditions (on average, 3097, 3063 and 344 saplings ha(-1), respectively), suggesting a strong competitive ability of these two species. Oak was present on 22% (43% for hornbeam and 68% for beech) of the studied plots, at a low density but with a height and DBH similar to that of beech or hornbeam. This result highlights the high dissemination capacity of beech and hornbeam, which prevents the establishment of a stand dominated by oak. When seeking to obtain oak-dominated stands in the lowlands of Europe, the abundance of beech and hornbeam can be a limiting factor that could lead to the disappearance of oak from large areas if no silvicultural operations are performed to promote it.

ano.nymous@ccsd.cnrs.fr.invalid (Lucie Dietz) 02 Feb 2023

https://hal.science/hal-03926051v1

[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

[hal-03739690] Molecular plasticity to soil water deficit differs between sessile oak (Quercus Petraea (Matt.) Liebl.) high- and low-water use efficiency genotypes.

Water use efficiency (WUE) is an important adaptive trait for soil water deficit. The molecular and physiological bases of WUE regulation in crops have been studied in detail in the context of plant breeding. Knowledge for most forest tree species lags behind, despite the need to identify populations or genotypes able to cope with the longer, more intense drought periods likely to result from climate warming.We aimed to bridge this gap in knowledge for sessile oak (Quercus petraeae (Matt.) L.), one of the most ecologically and economically important tree species in Europe, using a factorial design including trees with contrasted phenotypic values (low and high WUE) and two watering regimes (control and drought). By monitoring the ecophysiological response, we first qualified genotypes for their WUE (by using instantaneous and long-term measures). We then performed RNA-seq to quantify gene expression for the three most extreme genotypes exposed to the two watering regimes. By analyzing the interaction term, we were able to capture the molecular strategy of each group of plants for coping with drought. We identified putative candidate genes potentially involved in the regulation of transpiration rate in high WUE phenotypes. Regardless of water availability, trees from the high WUE phenotypic class overexpressed genes associated with drought responses, and in the control of stomatal density and distribution, and displayed a downregulation of genes associated with early stomatal closure and high transpiration rate. Fine physiological screening of sessile oaks with contrasting WUE, and their molecular characterization i) highlighted subtle differences in transcription between low and high WUE genotypes, identifying key molecular players in the genetic control of this trait, and ii) revealed the genes underlying the molecular strategy that evolved in each group to potentially cope with water deficit, providing new insight into the within species diversity in drought adaptation strategies.

ano.nymous@ccsd.cnrs.fr.invalid (Gregoire Le Provost) 28 Jul 2022

https://hal.inrae.fr/hal-03739690v1

[hal-04049772] Des forêts en libre évolution : une vision qui cherche encore sa place dans les politiques publiques, et un dossier scientifique encore lacunaire mais déjà intéressant

Ce numéro de la Revue forestière française, faute de connaissances scientifiques partout bien établies, n’aborde que marginalement certaines questions : il en est ainsi en particulier des contributions respectives des forêts gérées et des forêts en libre évolution comportant bois sénescents et bois mort, dans le stockage du carbone, et de la résilience présumée plus forte des forêts en libre évolution. En dépit de ces lacunes, ce numéro permet d’éclairer d’une part les enjeux d’une politique européenne de préservation des « primary and old-growth forests » et d’autre part de l’ensauvagement des campagnes du fait de la déprise agricole et forestière. Il montre enfin à quel point le débat technique et scientifique examiné est articulé à des points de vue culturels et éthiques concernant le rapport au sauvage, les relations entre l’humanité et la nature, et les vertus du lâcher-prise. Il illustre le bouillonnement actuel de réflexions et d’initiatives, avec leurs forces et leurs lacunes, ainsi que les défis à relever.

ano.nymous@ccsd.cnrs.fr.invalid (Christian Barthod) 28 Mar 2023

https://hal.sorbonne-universite.fr/hal-04049772v1

[hal-04453135] Drought affects the fate of non-structural carbohydrates in hinoki cypress

Tree species that close stomata early in response to drought are likely to suffer from an imbalance between limited carbohydrate supply due to reduced photosynthesis and metabolic demand. Our objective was to clarify the dynamic responses of non-structural carbohydrates to drought in a water-saving species, the hinoki cypress (Chamaecyparis obtusa Sieb. et Zucc.). To this end, we pulse-labeled young trees with 13CO2 10 days after the beginning of the drought treatment. Trees were harvested 7 days later, early during drought progression, and 86 days later when they had suffered from a long and severe drought. The labeled carbon (C) was traced in phloem extract, in the organic matter and starch of all the organs, and in the soluble sugars (sucrose, glucose and fructose) of the most metabolically active organs (foliage, green branches and fine roots). No drought-related changes in labeled C partitioning between belowground and aboveground organs were observed. The C allocation between non-structural carbohydrates was altered early during drought progression: starch concentration was lower by half in the photosynthetic organs, while the concentration of almost all soluble sugars tended to increase. The preferential allocation of labeled C to glucose and fructose reflected an increased demand for soluble sugars for osmotic adjustment. After 3 months of a lethal drought, the concentrations of soluble sugars and starch were admittedly lower in drought-stressed trees than in the controls, but the pool of non-structural carbohydrates was far from completely depleted. However, the allocation to storage had been impaired by drought; photosynthesis and the sugar translocation rate had also been reduced by drought. Failure to maintain cell turgor through osmoregulation and to refill embolized xylem due to the depletion in soluble sugars in the roots could have resulted in tree mortality in hinoki cypress, though the total pool of carbohydrate was not completely depleted.

ano.nymous@ccsd.cnrs.fr.invalid (Chiaki Tsuji) 12 Feb 2024

https://hal.science/hal-04453135v1

[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

[hal-04895169] Bark composition changes along the trunk of three softwood species: Picea abies , Abies alba Mill. and Pseudotsuga menziesii

[...]

ano.nymous@ccsd.cnrs.fr.invalid (Clément Fritsch) 17 Jan 2025

https://hal.univ-lorraine.fr/hal-04895169v1

[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

[hal-04033784] Plant invasion modifies isohydricity in Mediterranean tree species

Understanding of plant hydraulic strategies (i.e. the degree of iso-/anisohydricity) is crucial to predict the response of plants to changing environmental conditions such as climate-change induced extreme drought. Several abiotic factors, including evaporative demand, have been shown to seasonally modify the isohydricity of plants. However, the impact of biotic factors such as plant-plant interactions on hydraulic strategies has seldom been explored. Here, we investigated adaptations and changes in hydraulic strategies of two woody species in response to seasonal abiotic conditions, experimental drought and plant invasion in a Mediterranean cork oak (Quercus suber) ecosystem with a combined shrub invasion (Cistus ladanifer) and rain exclusion experiment. From the dry to wet season, Q. suber shifted from a partial isohydric to an anisohydric behaviour while C. ladanifer shifted from strict anisohydric to partial isohydric. During drought, water competition by plant invasion significantly modified the hydraulic strategy of invaded Q. suber, which was accompanied by lower pre-dawn leaf water potentials, sap flow density, leaf area index and trunk increment rates. This altered isohydricity of invaded Q. suber trees was most likely caused by interspecific competition for water resources by water spending C. ladanifer shrubs. Both species do have the highest proportion of fine roots in the topsoil and thus, an additional water consumer, such as C. ladanifer can lead to more stressful conditions for Q. suber during times of water scarcity. Further underlying mechanisms of the altered isohydricity of Q. suber, such as potential allelopathic effects of C. ladanifer exudates on root growth of Q. suber, have to be investigated in the future. In conclusion, we demonstrate that the degree of isohydricity of two woody Mediterranean plant species is dynamically determined by the interplay of species-specific hydraulic traits and their abiotic and biotic environment. Read the free Plain Language Summary for this article on the Journal blog.

ano.nymous@ccsd.cnrs.fr.invalid (Simon Haberstroh) 17 Mar 2023

https://hal.inrae.fr/hal-04033784v1

[hal-03926055] With increasing site quality asymmetric competition and mortality reduces Scots pine (Pinus sylvestris L.) stand structuring across Europe

Heterogeneity of structure can increase mechanical stability, stress resistance and resilience, biodiversity and many other functions and services of forest stands. That is why many silvicultural measures aim at enhancing structural diversity. However, the effectiveness and potential of structuring may depend on the site conditions. Here, we revealed how the stand structure is determined by site quality and results from site-dependent partitioning of growth and mortality among the trees. We based our study on 90 mature, even-aged, fully stocked monocultures of Scots pine (Pinus sylvestris L.) sampled in 21 countries along a productivity gradient across Europe. A mini-simulation study further analyzed the site-dependency of the interplay between growth and mortality and the resulting stand structure. The overarching hypothesis was that the stand structure changes with site quality and results from the site-dependent asymmetry of competition and mortality.First, we show that Scots pine stands structure across Europe become more homogeneous with increasing site quality. The coefficient of variation and Gini coefficient of stem diameter and tree height continuously decreased, whereas Stand Density Index and stand basal area increased with site index.Second, we reveal a site-dependency of the growth distribution among the trees and the mortality. With increasing site index, the asymmetry of both competition and growth distribution increased and suggested, at first glance, an increase in stand heterogeneity. However, with increasing site index, mortality eliminates mainly small instead of all-sized trees, cancels the size variation and reduces the structural heterogeneity.Third, we modelled the site-dependent interplay between growth partitioning and mortality. By scenario runs for different site conditions, we can show how the site-dependent structure at the stand level emerges from the asymmetric competition and mortality at the tree level and how the interplay changes with increasing site quality across Europe.Our most interesting finding was that the growth partitioning became more asymmetric and structuring with increasing site quality, but that the mortality eliminated predominantly small trees, reduced their size variation and thus reversed the impact of site quality on the structure. Finally, the reverse effects of mode of growth partitioning and mortality on the stand structure resulted in the highest size variation on poor sites and decreased structural heterogeneity with increasing site quality. Since our results indicate where heterogeneous structures need silviculture interventions and where they emerge naturally, we conclude that these findings may improve system understanding and modelling and guide forest management aiming at structurally rich forests.

ano.nymous@ccsd.cnrs.fr.invalid (Hans Pretzsch) 06 Jan 2025

https://hal.science/hal-03926055v1

[hal-03654399] Examination of aboveground attributes to predict belowground biomass of young trees

Just as the aboveground tree organs represent the interface between trees and the atmosphere, roots act as the interface between trees and the soil. In this function, roots take-up water and nutrients, facilitate interactions with soil microflora, anchor trees, and also contribute to the gross primary production of forests. However, in comparison to aboveground plant organs, the biomass of roots is much more difficult to study. In this study, we analyzed 19 European datasets on above- and belowground biomass of juvenile trees of 14 species to identify generalizable estimators of root biomass based on tree sapling dimensions (e.g. height, diameter, aboveground biomass). Such estimations are essential growth and sequestration modelling. In addition, the intention was to study the effect of sapling dimension and light availability on biomass allocation to roots. All aboveground variables were significant predictors for root biomass. But, among aboveground predictors of root biomass plant height performed poorest. When comparing conifer and broadleaf species, the latter tended to have a higher root biomass at a given dimension. Also, with increasing size, the share of belowground biomass tended to increase for the sapling dimensions considered. In most species, there was a trend of increasing relative belowground biomass with increasing light availability. Finally, the height to diameter ratio (H/D) was negatively correlated to relative belowground biomass. This indicates that trees with a high H/D are not only more unstable owing to the unfavorable bending stress resistance, but also because they are comparatively less well anchored in the ground. Thus, single tree stability may be improved through increasing light availability to increase the share of belowground biomass.

ano.nymous@ccsd.cnrs.fr.invalid (Peter Annighöfer) 28 Apr 2022

https://hal.inrae.fr/hal-03654399v1

[hal-03863446] Genotypic and tissue-specific variation of Populus nigra transcriptome profiles in response to drought

Climate change is one of the most important challenges for mankind in the far and near future. In this regard, sustainable production of woody crops on marginal land with low water availability is a major challenge to tackle. This dataset is part of an experiment, in which we exposed three genetically differentiated genotypes of Populus nigra originating from contrasting natural habitats to gradually increasing moderate drought. RNA sequencing was performed on fine roots, developing xylem and leaves of those three genotypes under control and moderate drought conditions in order to get a comprehensive dataset on the transcriptional changes at the whole plant level under water limiting conditions. This dataset has already provided insight in the transcriptional control of saccharification potential of the three Populus genotypes under drought conditions and we suggest that our data will be valuable for further in-depth analysis regarding candidate gene identification or, on a bigger scale, for meta-transcriptome analysis.

ano.nymous@ccsd.cnrs.fr.invalid (Christian Eckert) 30 Jun 2024

https://hal.inrae.fr/hal-03863446v1

[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 Oct 2023

https://hal.science/hal-03502713v1

[hal-04126514] AquaDesign: A tool to assist aquaculture production design based on abiotic requirements of animal species

Farming new species and promoting polyculture can enhance aquaculture sustainability. This implies to define the rearing conditions that meet the ecological requirements of a target species and/or to assess if different species can live in the same farming environment. However, there is a large number of rearing conditions and/or taxon combinations that can be considered. In order to minimise cumbersome and expensive empirical trials to explore all possibilities, we introduce a tool, AquaDesign. It is based on a R-script and package which help to determine farming conditions that are most likely suitable for species through in silico assessment. We estimate farming conditions potentially suitable for an aquatic organism by considering the species niche. We define the species n-dimensional niche hypervolume using a correlative approach in which the species niche is estimated by relating distribution data to environmental conditions. Required input datasets are mined from several public databases. The assistant tool allows users to highlight (i) abiotic conditions that are most likely suitable for species and (ii) combinations of species potentially able to live in the same abiotic environment. Moreover, it offers the possibility to assess if a particular set of abiotic conditions or a given farming location is potentially suitable for the monoculture or the polyculture of species of interest. Our tool provides useful pieces of information to develop freshwater aquacultures. Using the large amount of biogeographic and abiotic information available in public databases allows us to propose a pragmatic and operational tool even for species for which abiotic requirements are poorly or not available in literature such as currently non-produced species. Overall, we argue that the assistant tool can act as a stepping stone to promote new aquatic productions which are required to enhance aquaculture sustainability.

ano.nymous@ccsd.cnrs.fr.invalid (Grégoire Butruille) 13 Jun 2023

https://hal.science/hal-04126514v1

[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

[hal-04327133] Variability in Stem Methane Emissions and Wood Methane Production of Different Tree Species in a Cold Temperate Mountain Forest

The role of trees, in addition to that of the soil, must be considered in CH4 budget for forests. Although trees can emit CH4 through their stems, there are uncertainties about the main factors that explain inter- and intraspecific variations, which impedes upscaling of measurements from the stem to the ecosystem level. This study aimed to characterize the variability in CH4 emissions (F-CH4) from stems between species and individuals, and within individuals. We measured F-CH4 in situ during the snow-free period in five species in a temperate mountain forest, using individuals of different sizes and chambers at different heights along the stems. One coniferous species emitted almost no CH4, whereas four broadleaved species exhibited high intraspecific variability in F-CH4 (0-3.7 nmol m(-2) s(-1)). Increasing trends in F-CH4 with tree diameter were observed for four species. The vertical patterns in F-CH4 were complex. Seasonal variations in F-CH4, measured on two trees per species, were well explained by air temperature with apparent temperature sensitivity coefficients (Q(10)) between 1.2 and 2, which were not related to the antecedent precipitation indices, whether calculated over 7 or 30 days. Potential CH4 production was detected in wood core segments incubated under anoxic conditions in the majority of individual trees of all species. Our results suggest that the CH4 emitted by trunks can originate either from soil or internal sources. Scaling F-CH4 from trees at the stand level and developing process-based models of F-CH4 will remain challenging until the sources of variation are better explained.

ano.nymous@ccsd.cnrs.fr.invalid (Daniel Epron) 06 Dec 2023

https://hal.inrae.fr/hal-04327133v1

[hal-03858826] Potential soil methane oxidation in naturally regenerated oak-dominated temperate deciduous forest stands responds to soil water status regardless of their age—an intact core incubation study

Key message: Potential CH 4 oxidation in the top soil layer increased with decreasing soil water content in spring but was inhibited during severe summer drought in naturally-regenerated oak-dominated temperate deciduous forest stands regardless of their age. No direct effect of mineral nitrogen on soil CH 4 oxidation was found. Soil CH 4 oxidation in temperate forests could be reduced by extreme climatic events. Context: The oxidation of atmospheric methane (CH 4) by methanotrophic bacteria in forest soils is an important but overlooked ecosystem service. Aim: Our objective was to determine which factors drive variations in soil CH 4 oxidation in oak-dominated temperate deciduous forest stands of different ages. Methods: Soil samples were collected in 16 stands aged 20 to 143 years in periods of high and low soil water content (SWC). The potential rate of soil CH 4 oxidation was measured by incubating the first five centimetres of intact soil cores at 20 °C. Results: SWC was the main driver accounting for variations in CH 4 oxidation. In spring, a twofold reduction in SWC greatly increased CH 4 oxidation. But when the soil was dry in late summer, a further reduction in SWC led to a decrease in CH 4 oxidation in the top soil layer. No direct effect of mineral nitrogen on soil CH 4 oxidation was found. Conclusions: With regard to soil CH 4 oxidation, naturally regenerated forest stands contribute equally to climate change mitigation regardless of their age. Considering future climate scenarios for Europe, soil CH 4 sink in temperate forests could be reduced, due to both an increase in the number of flooding episodes in spring and drier summers.

ano.nymous@ccsd.cnrs.fr.invalid (Nicolas Bras) 17 Nov 2022

https://hal.univ-lorraine.fr/hal-03858826v1

[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

[hal-03613329] Parenchyma fractions drive the storage capacity of non‐structural carbohydrates across a broad range of tree species

Premise: Nonstructural carbohydrates (NSC) play a key role in tree performance and functioning. NSC are stored in radial and axial parenchyma (RAP) cells, but it is not known if this relationship is altered among species and climates, or is linked to functional traits describing xylem structure (wood density) and tree stature.Methods: In a systematic review, we collated data for NSC content and RAP fractions in stems for 68 tree species. To examine their relationships with climate factors and other functional traits, we also recovered climate data at each tree's location, as well as wood density and maximum height. A phylogenetic tree was established to examine the role of species’ evolutionary relationships on the associations between NSC, RAP and functional traits.Key Results: Across all 68 tree species, NSC was positively correlated with RAP and mean annual temperature. but relationships were only weakly significant in temperate species and angiosperms. When separating RAP into radial parenchyma (RP) and axial parenchyma (AP), both NSC and wood density were positively correlated with RP but not with AP. Taller trees had less dense wood and lower RAP, but no relationship with NSC.Conclusions: NSC is stored mostly in radial parenchyma that increases in warmer climates, but this relationship was only weakly linked to wood density and tree height. Our analysis of evolutionary relationships demonstrated that RAP fractions and NSC content were always closely related, suggesting that RAP can act as a reliable proxy for potential NSC storage capacity in tree stems.

ano.nymous@ccsd.cnrs.fr.invalid (Guangqi Zhang) 18 Mar 2022

https://hal.inrae.fr/hal-03613329v1

[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

[hal-04321804] A critical thermal transition driving spring phenology of Northern Hemisphere conifers

Despite growing interest in predicting plant phenological shifts, advanced spring phenology by global climate change remains debated. Evidence documenting either small or large advancement of spring phenology to rising temperature over the spatio‐temporal scales implies a potential existence of a thermal threshold in the responses of forests to global warming. We collected a unique data set of xylem cell‐wall‐thickening onset dates in 20 coniferous species covering a broad mean annual temperature (MAT) gradient (−3.05 to 22.9°C) across the Northern Hemisphere (latitudes 23°–66° N). Along the MAT gradient, we identified a threshold temperature (using segmented regression) of 4.9 ± 1.1°C, above which the response of xylem phenology to rising temperatures significantly decline. This threshold separates the Northern Hemisphere conifers into cold and warm thermal niches, with MAT and spring forcing being the primary drivers for the onset dates (estimated by linear and Bayesian mixed‐effect models), respectively. The identified thermal threshold should be integrated into the Earth‐System‐Models for a better understanding of spring phenology in response to global warming and an improved prediction of global climate‐carbon feedbacks.

ano.nymous@ccsd.cnrs.fr.invalid (Jian‐guo Huang) 04 Dec 2023

https://hal.inrae.fr/hal-04321804v1

[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

[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

[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

[hal-03639012] Climate and ungulate browsing impair regeneration dynamics in spruce-fir-beech forests in the French Alps

Abstract Key message Different components of water balance and temperature reduce density and height growth of saplings of Picea abies (L.) H. Karst (Norway spruce), Abies alba Mill. (silver fir) and Fagus sylvatica L. (European beech) in mixed uneven-aged forests in the French Alps and Jura mountains. Ungulate browsing is an additional pressure on fir and beech that could jeopardise the renewal of these species in the future. Context The uncertainty in tree recruitment rates raises questions about the factors affecting regeneration processes in forests. Factors such as climate, light, competition and ungulate browsing pressure may play an important role in determining regeneration, forest structures and thus future forest composition. Aims The objective of this study was to quantify sapling densities and height increments of spruce, fir and beech and to identify dominant environmental variables influencing them in mixed uneven-aged forests in the French Alps and Jura mountains. Methods Sapling height increment and density were recorded in 152 plots, and non-linear mixed models were obtained to establish relations between them and environmental factors known to affect regeneration, namely altitude, slope, aspect, canopy openness, soil characteristics, temperature, precipitation and ungulate browsing. Results Regeneration density, varying from 0 to 7 saplings per m 2 , decreased with sapling height and was also negatively affected for spruce by PET, but positively for fir by precipitation and for beech by mean annual soil water content. Height increment reached up to 50 cm annually, increasing with sapling height and canopy openness and decreasing under high maximum summer temperatures for spruce and beech. The statistical effect of different environmental variables varied slightly among species but trends were quite similar. Additionally, ungulate browsing was high, with fir being the most intensely browsed, followed closely by beech, while spruce was rarely browsed. Conclusions All these results suggest that more temperature warming and a decrease in water availability could negatively impact sapling growth and density in the three species, with possible reduction of forest renewal fluxes. The observed increase of ungulate populations leading to increased browsing could be particularly detrimental to fir saplings.

ano.nymous@ccsd.cnrs.fr.invalid (Mithila Unkule) 12 Apr 2022

https://hal.inrae.fr/hal-03639012v1

[hal-03638143] Historical landscape matters for threatened species in French mountain forests

Ancient forests are known to host a biodiversity of high ecological distinctiveness and are likely to provide habitat for red-listed species. Yet, few studies have investigated the role of forest continuity for the conservation of threatened species. We used species-presence data on red-listed species from 12 taxonomic groups (Spermatophyta, Pteridophyta, Bryophyta, Lichens, Chiroptera, Aves, Squamata, Amphibia, Coleoptera, Lepidoptera, Odonata and Orthoptera) to ascertain if ancient forests are an important habitat for threatened species in five mountain and subalpine protected areas in France. We compared the effect of the amount of historical forest (1853–1860) with the effect of the amount of current forest on the distribution of red-listed species in six circular landscape buffers ranging in radius from 100 to 1500 m. We showed that the amount of historical forest in the landscape had a positive effect on forest Spermatophyta, Bryophyta, Coleoptera and edge forest Pteridophyta with a better predictive power than current forest area, highlighting a colonization credit in recent forests. Conversely, edge-forest lepidopterans were more negatively affected by historical than by current forest area, highlighting an extinction debt in recent forests. Our findings underline that implementing protective measures of ancient forests would be a better strategy than afforestation to preserve threatened forest species in mountain and subalpine forest landscapes.

ano.nymous@ccsd.cnrs.fr.invalid (Sylvain Mollier) 23 Nov 2023

https://hal.inrae.fr/hal-03638143v1

[hal-03846703] Stronger legacy effects of cropland than of meadows or pastures on soil conditions and plant communities in French mountain forests

Question Differences in understory vegetation between ancient and recent forests have been thoroughly explored; however, few studies have investigated the legacies of different former land uses in recent forests. Indeed, due to more intense agricultural practices (tillage and fertilisation), legacy effects are expected to be stronger in former cropland or meadows than in former pastures. Our objectives were to compare soil conditions, taxonomic composition and functional composition of understory plant communities in recent forests located on former pastures, meadows or cropland, with ancient forests as a reference.LocationTarentaise Valley, Savoy, France Methods Based on land-use maps surveyed between 1862 and 1864, we selected 82 forest sites with different former land uses in mountain forests in the French Alps and carried out soil sampling and botanical surveys. To account for potential confounding factors (altitude, canopy cover, tree species composition), we applied multiple linear regressions to analyse soil properties, canonical correspondence analysis to analyse plant taxonomic composition and multi-species generalized linear mixed-effects models to analyse relationships between plant functional composition and former land uses. Results The soils of former cropland were richer in nutrients and more alkaline compared to other past land uses, while soils on former pastures and meadows differed only slightly from ancient forests. Ancient forests were characterised by acidophilic, shade-tolerant, low-stature, forest-dependent species, whereas former cropland was characterised by calcicolous non-forest species. Former pasture and meadow communities displayed a distinct taxonomic composition compared to other past land uses, but a functional composition closer to ancient forest than to former cropland. Conclusion Former cropland has a stronger legacy effect than former pastures or meadows. This could explain small differences between ancient and recent forests observed in previous studies conducted in mountain landscapes where former cropland was rare.

ano.nymous@ccsd.cnrs.fr.invalid (Sylvain Mollier) 23 Nov 2023

https://hal.inrae.fr/hal-03846703v1

[hal-03517053] Identifying the main drivers of the seasonal decline of near-infrared reflectance of a temperate deciduous forest

The physical mechanisms behind correlations of earth observations and remote sensing products are of vital importance. The so-called 'near-infrared reflectance of vegetation' (NIR V) and gross primary production (GPP) show high correlations among different ecosystems and temporal scales but the underlying relationship is still poorly understood. NIR V is defined as the product of normalized difference vegetation index (NDVI) and nearinfrared (NIR) canopy reflectance (R NIR). We examined this relationship in the case of a temperate deciduous forest in Germany. GPP, R NIR and NIR V all exhibited a strong rise during leaf development in spring and a continual decline after the maximum in early summer. The decline of NIR V in late summer was mainly driven by the decline of R NIR , since NDVI remained saturated. Here we tested the R NIR decline attributions to changes in leaf area index, leaf optical properties, canopy structure, sun-sensor geometry, or understory vegetation by measuring seasonal variations of those factors of the temperate deciduous forest. Leaf area was nearly constant between May and mid September, leaf albedo decreased slightly, leaf angles increased over time towards more vertical leaves, and understory reflectance decreased considerably. We simulated the seasonal R NIR decline of the forest using the radiative transfer model FRT and quantified the sensitivity of the decline to variations in the measured parameters. FRT captured well the observed seasonal R NIR decline by Sentinel 2 using the measured optical and structural properties. Decreasing understory reflectance alone explained 43% of the simulated R NIR decrease, while leaf angle variations explained 31%, the solar zenith angle (SZA) 21%, leaf albedo 7%, and LAI 0%. The effect size of the SZA depended on the viewing angle and would hence be different for different satellites and for local instruments. The results may help to better understand and help to track seasonal changes in forest structure and leaf optical properties using remote sensing techniques. They also suggest that the proposed link between the seasonal evolution of GPP and NIR V may be weaker than expected.

ano.nymous@ccsd.cnrs.fr.invalid (Niklas Hase) 07 Jan 2022

https://hal.inrae.fr/hal-03517053v1

Catégorie de cookie	Moyens de désactivation
Cookies analytiques et de performance	Realytics Google Analytics Spoteffects Optimizely
Cookies de ciblage ou publicitaires	DoubleClick Mediarithmics

Cookies obligatoires	Cookies fonctionnels	Cookies sociaux et publicitaires
Ces cookies sont nécessaires au bon fonctionnement du site, ils ne peuvent pas être désactivés. Ils nous sont utiles pour vous fournir une connexion sécuritaire et assurer la disponibilité a minima de notre site internet.	Ces cookies nous permettent d’analyser l’utilisation du site afin de pouvoir en mesurer et en améliorer la performance. Ils nous permettent par exemple de conserver vos informations de connexion et d’afficher de façon plus cohérente les différents modules de notre site.	Ces cookies sont utilisés par des agences de publicité (par exemple Google) et par des réseaux sociaux (par exemple LinkedIn et Facebook) et autorisent notamment le partage des pages sur les réseaux sociaux, la publication de commentaires, la diffusion (sur notre site ou non) de publicités adaptées à vos centres d’intérêt.
Sur nos CMS EZPublish, il s’agit des cookies sessions CAS et PHP et du cookie New Relic pour le monitoring (IP, délais de réponse). Ces cookies sont supprimés à la fin de la session (déconnexion ou fermeture du navigateur)	Sur nos CMS EZPublish, il s’agit du cookie XiTi pour la mesure d’audience. La société AT Internet est notre sous-traitant et conserve les informations (IP, date et heure de connexion, durée de connexion, pages consultées) 6 mois.	Sur nos CMS EZPublish, il n’y a pas de cookie de ce type.

Productions 2022

HAL : Dernières publications

[hal-03518443] Global maps of soil temperature

[hal-03714709] A standardized morpho-functional classification of the planet's humipedons

[hal-03543468] Sphagnum physiological responses to elevated temperature, nitrogen, CO2 and low moisture in laboratory and in situ microhabitats: a review

[hal-03658479] Traceability and quality assessment of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) logs: the TreeTrace_Douglas database

[hal-04054146] Characterizing the calibration domain of remote sensing models using convex hulls

[hal-03926054] Identification and spatial extent of understory plant species requiring vegetation control to ensure tree regeneration in French forests

[hal-03468938] CNN-based Method for Segmenting Tree Surface Singularites

[hal-03903795] Modeling and propagating inventory‐based sampling uncertainty in the large‐scale forest demographic model “MARGOT”

[hal-03768111] Multisource forest inventories: A model-based approach using k-NN to reconcile forest attributes statistics and map products

[hal-03694879] Climate change-induced background tree mortality is exacerbated towards the warm limits of the species ranges

[hal-03518448] Tropical and subtropical Asia's valued tree species under threat

[hal-03880260] Regional climate moderately influences species-mixing effect on tree growth-climate relationships and drought resistance for beech and pine across Europe

[hal-03807910] Co-limitation towards lower latitudes shapes global forest diversity gradients

[hal-03554126] The number of tree species on Earth

[hal-03343133] Drought stress recovery of hydraulic and photochemical processes in Neotropical tree saplings

[hal-04327109] A review of the heterogeneous landscape of biodiversity databases: opportunities and challenges for a synthesized biodiversity knowledge base

[hal-03873631] High exposure of global tree diversity to human pressure

[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

[hal-03721086] Water table depth modulates productivity and biomass across Amazonian forests

[hal-04226870] The 2018 hot drought pushed conifer wood formation to the limit of its plasticity : Consequences for woody biomass production and tree ring structure

[hal-04226892] Wood Formation Modeling – A Research Review and Future Perspectives

[hal-03888147] No matter how much space and light are available, radial growth distribution in Fagus sylvatica L. trees is under strong biomechanical control

[hal-03926051] Beech and hornbeam dominate oak 20 years after the creation of storm-induced gaps

[hal-03432028] Transferability of an individual- and trait-based forest dynamics model: A test case across the tropics

[hal-03739690] Molecular plasticity to soil water deficit differs between sessile oak (Quercus Petraea (Matt.) Liebl.) high- and low-water use efficiency genotypes.

[hal-04049772] Des forêts en libre évolution : une vision qui cherche encore sa place dans les politiques publiques, et un dossier scientifique encore lacunaire mais déjà intéressant

[hal-04453135] Drought affects the fate of non-structural carbohydrates in hinoki cypress

[hal-03519397] Do trait responses to simulated browsing in Quercus robur saplings affect their attractiveness to Capreolus capreolus the following year?

[hal-04895169] Bark composition changes along the trunk of three softwood species: Picea abies , Abies alba Mill. and Pseudotsuga menziesii

[hal-03647971] Effect of tree demography and flexible root water uptake for modeling the carbon and water cycles of Amazonia

[hal-04033784] Plant invasion modifies isohydricity in Mediterranean tree species

[hal-03926055] With increasing site quality asymmetric competition and mortality reduces Scots pine (Pinus sylvestris L.) stand structuring across Europe

[hal-03654399] Examination of aboveground attributes to predict belowground biomass of young trees

[hal-03863446] Genotypic and tissue-specific variation of Populus nigra transcriptome profiles in response to drought

[hal-03502713] Uncovering the critical soil moisture thresholds of plant water stress for European ecosystems

[hal-04126514] AquaDesign: A tool to assist aquaculture production design based on abiotic requirements of animal species

[hal-03880254] The 2018 European heatwave led to stem dehydration but not to consistent growth reductions in forests

[hal-04327133] Variability in Stem Methane Emissions and Wood Methane Production of Different Tree Species in a Cold Temperate Mountain Forest

[hal-03858826] Potential soil methane oxidation in naturally regenerated oak-dominated temperate deciduous forest stands responds to soil water status regardless of their age—an intact core incubation study

[hal-03678147] Do <sup>2</sup> H and <sup>18</sup> O in leaf water reflect environmental drivers differently?

[hal-03613329] Parenchyma fractions drive the storage capacity of non‐structural carbohydrates across a broad range of tree species

[hal-03736228] Non-structural carbohydrates and morphological traits of leaves, stems and roots from tree species in different climates

[hal-04321804] A critical thermal transition driving spring phenology of Northern Hemisphere conifers

[hal-04456551] Comportement des chênes pédonculé et sessile sur deux sols à engorgement temporaire en Lorraine

[hal-03643415] A limited number of species is sufficient to assign a vegetation plot to a forest vegetation unit

[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

[hal-03639012] Climate and ungulate browsing impair regeneration dynamics in spruce-fir-beech forests in the French Alps

[hal-03638143] Historical landscape matters for threatened species in French mountain forests

[hal-03846703] Stronger legacy effects of cropland than of meadows or pastures on soil conditions and plant communities in French mountain forests

[hal-03517053] Identifying the main drivers of the seasonal decline of near-infrared reflectance of a temperate deciduous forest