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[hal-01594863] Diversity and carbon storage across the tropical forest biome
Tropical forests are global centres of biodiversity and carbon storage. Many tropical countries aspire to protect forest to fulfil biodiversity and climate mitigation policy targets, but the conservation strategies needed to achieve these two functions depend critically on the tropical forest tree diversity-carbon storage relationship. Assessing this relationship is challenging due to the scarcity of inventories where carbon stocks in aboveground biomass and species identifications have been simultaneously and robustly quantified. Here, we compile a unique pan-tropical dataset of 360 plots located in structurally intact old-growth closed-canopy forest, surveyed using standardised methods, allowing a multi-scale evaluation of diversity-carbon relationships in tropical forests. Diversity-carbon relationships among all plots at 1 ha scale across the tropics are absent, and within continents are either weak (Asia) or absent (Amazonia, Africa). A weak positive relationship is detectable within 1 ha plots, indicating that diversity effects in tropical forests may be scale dependent. The absence of clear diversity-carbon relationships at scales relevant to conservation planning means that carbon-centred conservation strategies will inevitably miss many high diversity ecosystems. As tropical forests can have any combination of tree diversity and carbon stocks both require explicit consideration when optimising policies to manage tropical carbon and biodiversity.
ano.nymous@ccsd.cnrs.fr.invalid (Martin J. P. Sullivan) 26 Sep 2017
https://hal.science/hal-01594863v1
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[hal-01852904] Mapping local and global variability in plant trait distributions
Our ability to understand and predict the response of ecosystems to a changing environment depends on quantifying vegetation functional diversity. However, representing this diversity at the global scale is challenging. Typically, in Earth system models, characterization of plant diversity has been limited to grouping related species into plant functional types (PFTs), with all trait variation in a PFT collapsed into a single mean value that is applied globally. Using the largest global plant trait database and state of the art Bayesian modeling, we created fine-grained global maps of plant trait distributions that can be applied to Earth system models. Focusing on a set of plant traits closely coupled to photosynthesis and foliar respiration-specific leaf area (SLA) and dry mass-based concentrations of leaf nitrogen (N-m) and phosphorus (P-m), we characterize how traits vary within and among over 50,000 similar to 50 x 50-km cells across the entire vegetated land surface. We do this in several ways-without defining the PFT of each grid cell and using 4 or 14 PFTs; each model's predictions are evaluated against out-of-sample data. This endeavor advances prior trait mapping by generating global maps that preserve variability across scales by using modern Bayesian spatial statistical modeling in combination with a database over three times larger than that in previous analyses. Our maps reveal that the most diverse grid cells possess trait variability close to the range of global PFT means.
ano.nymous@ccsd.cnrs.fr.invalid (Ethan Butler) 26 May 2020
https://hal.science/hal-01852904v1
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[hal-04651347] Genetic Diversity of Water Use Efficiecy in forest trees
Forest trees are organisms which can have very large geographic distributions and therefore cover a large range of different environmental conditions. In forestry, comparative plantations have been used for a century to compare different provenances of trees for their growth. Such plantations have been used by ecophysiologists to use carbon stable isotopes to screen for variation in water use efficiency, and large population differences have been shown for many species, suggesting a genetic determinism for this traits and perhaps indicating local adaptations. Different crossings (open pollination, half-sibs, full-sibs) can be used to either estimate more precisely the genetic control on this trait (heritability) or to determine the genetic regions (QTL) as well as the genes underlying the observed variation. The running project H2Oak (https://www6.inra.fr/anr-h2oak/) takes this approach for Q. robur L. and Q. petraea (Matt.) Liebl. Recent advances will be shown and future approaches will be discussed.
ano.nymous@ccsd.cnrs.fr.invalid (Didier Le Thiec) 17 Jul 2024
https://hal.inrae.fr/hal-04651347v1
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[hal-02626794] Biodiversity and ecosystem functioning relations in European forests depend on environmental context
The importance of biodiversity in supporting ecosystem functioning is generally well accepted. However, most evidence comes from small-scale studies, and scaling-up patterns of biodiversity-ecosystem functioning (B-EF) remains challenging, in part because the importance of environmental factors in shaping B-EF relations is poorly understood. Using a forest research platform in which 26 ecosystem functions were measured along gradients of tree species richness in six regions across Europe, we investigated the extent and the potential drivers of context dependency of B-EF relations. Despite considerable variation in species richness effects across the continent, we found a tendency for stronger B-EF relations in drier climates as well as in areas with longer growing seasons and more functionally diverse tree species. The importance of water availability in driving context dependency suggests that as water limitation increases under climate change, biodiversity may become even more important to support high levels of functioning in European forests.
ano.nymous@ccsd.cnrs.fr.invalid (Sophia Ratcliffe) 26 May 2020
https://hal.inrae.fr/hal-02626794v1
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[halshs-01685563] Élevage et forêt sur la montagne dijonnaise à la fin du Moyen Âge. Deux établissements forestiers d’éleveurs en Terre de Saint-Seine Saint-Martin-du-Mont (Côte d’Or)
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ano.nymous@ccsd.cnrs.fr.invalid (Patrice Beck) 16 Jan 2018
https://shs.hal.science/halshs-01685563v1
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[hal-01577489] Tree size and local neighbourhood affect foliar nutrient content in a mixed plantation of beech ( Fagus sylvatica ) and maple ( Acer pseudoplatanus )
Whereas improved tree mineral nutrition is known to be one driver behind the higher growth in mixed vs pure stands, the effects of stand density and admixture of species with limited functional dissimilarity remain very poorly documented. Our study therefore addresses the impact of local neighbourhood, including density and species composition, on tree nutrition for two species with a limited contrast in traits. We investigated foliar nutrition in a young mixed plantation of beech (Fagus sylvatica L.) and sycamore maple (Acer pseudoplatanus L), planted along a double gradient of density and species proportion. Target trees of both species were selected over the full diameter range along this double gradient, and neighbourhood (local density, species identity and diversity) was determined in a 3 m radius. Using standardized regression analysis, we investigated direct effects of tree size and neighbourhood, and indirect effects of neighbourhood through tree size. Mostly we observed positive tree size effects in both species, be it stronger in beech. For maple, direct positive species identity effects were observed for C, N, P, S, K, Mg, Mn, Zn and Al. For beech, we found indirect negative effects of stand density and diversity. These results were in general agreement with growth data, which suggests that nutrition is one of the driving factors behind complementarity in this stand. We conclude that at this stage the effect of tree size dominates over the neighbourhood effects, including density and diversity. However, the presence of beech reduced intraspecific competition in maple with a positive effect on the foliar nutrient content. As neighbourhood effects are expected to increase as the plantation matures, our findings highlight the potential of admixing tree species with limited dissimilarity in traits for practical use in forestry.
ano.nymous@ccsd.cnrs.fr.invalid (Hans Nickmans) 25 Aug 2017
https://hal.science/hal-01577489v1
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[hal-02096805] Forest recovery since 1860 in a Mediterranean region: drivers and implications for land use and land cover spatial distribution
Context Land use and land cover (LULC) change is a major part of environmental change. Understanding its long-term causes is a major issue in landscape ecology. Objectives Our aim was to characterise LULC transitions since 1860 and assess the respective and changing effects of biophysical and socioeconomic drivers on forest, arable land and pasture in 1860, 1958 and 2010, and of biophysical, socioeconomic and distance from pre-existing forest on forest recovery for the two time intervals. Methods We assessed LULC transitions by superimposing 1860, 1958 and 2010 LULCs using a regular grid of 1 9 1 km points, in a French Mediterranean landscape (195,413 ha). We tested the effects of drivers using logistic regressions, and quantified pure and joint effects by deviance partitioning. Results Over the whole period, the three main LULCs were spatially structured according to land accessibility and soil productivity. LULC was driven more by socioeconomic than biophysical drivers in 1860, but the pattern was reversed in 2010. A widespread forest recovery mainly occurred on steeper slopes, far from houses and close to pre-existing forest, due to traditional practice abandonment. Forest recovery was better explained by biophysical than by socioeconomic drivers and was more dependent on distance from pre-existing forest between 1958 and 2010. Conclusions: Our results showed a shift in drivers of LULC and forest recovery over the last 150 years. Contrary to temperate regions, the set-aside of agricultural practices on difficult land has strengthened the link between biophysical drivers and LULC distribution over the last
ano.nymous@ccsd.cnrs.fr.invalid (Juliet Abadie) 03 May 2019
https://hal.science/hal-02096805v1
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[hal-02608142] Déterminants du changement du couvert forestier depuis 1860 dans le parc naturel régional du Luberon et implications pour la répartition des forêts actuelles
Après des siècles de diminution de sa surface, la forêt a connu un minimum historique en France vers le début du XIXe siècle puis a augmenté depuis, notamment en Provence. Les déterminants biophysiques, socioéconomiques et paysagers de ces changements forestiers à long terme ont cependant été assez peu explorés. Cette étude vise à analyser les transitions des principaux usages des terres depuis 1860 ainsi que l’évolution de l’effet de déterminants biophysiques (topographie, géologie), socioéconomiques (bâti, démographie) et paysagers (distance aux forêts préexistantes) sur la forêt et la reconquête forestière entre 1860 et 2010 dans le parc naturel régional du Luberon. Nous montrons que la forêt s’est maintenue jusqu’en 1860 et est réapparue depuis dans les secteurs les moins accessibles et productifs (pente forte, substrats durs, loin du bâti). En dernier lieu, nous précisons les différences de conditions biophysiques entre forêts actuelles selon leur continuité temporelle. En conclusion, nous discutons des implications de cette reconquête forestière.
ano.nymous@ccsd.cnrs.fr.invalid (Juliet Abadie) 24 Nov 2021
https://hal.inrae.fr/hal-02608142v1
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[hal-02737110] What drives the inter-annual variations in C flux and balance in a tropical rainforest of French Guiana?
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ano.nymous@ccsd.cnrs.fr.invalid (Maricar Aguilos) 02 Jun 2020
https://hal.inrae.fr/hal-02737110v1
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[hal-01652926] A tool to design fuzzy decision trees for sustainability assessment
Assessment of sustainability is a multicriteria problem that addresses several criteria belonging tovarious themes structured in sustainability dimensions. There is the need for a relevant aggregationmethod in addition to the disaggregated indicators. To face this challenge, we developed a new aggregationmethod, CONTRA, which is based on a decision tree using fuzzy sets. We attempted to combinethe advantages of previous tools like DEXi and FisPro that ensure simplicity, flexibility and transparencywhile limiting subjectivity in the design of decision trees. The results of two examples of implementationin the agricultural sector and a sensitivity test highlight the functionalities of the tool and its discriminationpotential. The possibility offered by the tool to correct predetermined decision rules makes itpossible to cope with compensation between input variables, an important issue in aggregation. The nextstep will be the finalisation of the Excel prototype in a user-friendly software
ano.nymous@ccsd.cnrs.fr.invalid (Christian Bockstaller) 30 Nov 2017
https://hal.science/hal-01652926v1
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[hal-01606915] How do leaf and ecosystem measures of water-use efficiency compare?
The terrestrial carbon and water cycles are intimately linked: the carbon cycle is driven by photosynthesis, while the water balance is dominated by transpiration, and both fluxes are controlled by plant stomatal conductance. The ratio between these fluxes, the plant water-use efficiency (WUE), is a useful indicator of vegetation function. WUE can be estimated using several techniques, including leaf gas exchange, stable isotope discrimination, and eddy covariance. Here we compare global compilations of data for each of these three techniques. We show that patterns of variation in WUE across plant functional types (PFTs) are not consistent among the three datasets. Key discrepancies include the following: leaf-scale data indicate differences between needleleaf and broadleaf forests, but ecosystem-scale data do not; leaf-scale data indicate differences between C3 and C4 species, whereas at ecosystem scale there is a difference between C3 and C4 crops but not grasslands; and isotope-based estimates of WUE are higher than estimates based on gas exchange for most PFTs. Our study quantifies the uncertainty associated with different methods of measuring WUE, indicates potential for bias when using WUE measures to parameterize or validate models, and indicates key research directions needed to reconcile alternative measures of WUE.
ano.nymous@ccsd.cnrs.fr.invalid (Belinda E. Medlyn) 03 Oct 2017
https://hal.science/hal-01606915v1
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[hal-02787886] The impact of microbial carbonic anhydrase activity on atmospheric concentrations of CO18O and COS at large scales
Photosynthesis (GPP), the largest CO 2 flux from the land surface, i s currently estimated with considerable uncertainty between 100-175 Pg C yr -1 . More robust estimates of global GPP could be obtained from the atmospheric b udgets of other tracers such as, the oxygen isotopic composition (δ 18 O) of atmospheric CO 2 or carbonyl sulphide (COS). However, estimating GPP using thes e tracers hinges on a better understanding of how soil microbes modify th e atmospheric concentrations of CO 18 O and COS at large scales. In par ticular, understanding better the role and activity of the enzyme Carbonic Anhydrase (CA) in soil microbes is a critical factor u nderpinning the successful implementation of these tracers in global scale models. We addr essed this knowledge gap by measuring the exchange of CO 18 O and COS between soil microcosms and the atmosphere from over 60 sites covering a range of biome s across Europe and the USA. This novel dataset has led to the development of a new mechanistic framework that can be easily i mplemented in mult i-tracer Earth system models to predict variati ons in soil CA a ctivity across the terrestrial land surface. Using this multi-tracer approach we provi de independent estimates of globa l GPP constrained by the atmospheric budgets of CO 2 , CO 18 O and COS.
ano.nymous@ccsd.cnrs.fr.invalid (Matthias Cuntz) 05 Jun 2020
https://hal.inrae.fr/hal-02787886v1
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[hal-01608422] Tree diversity drives forest stand resistance to natural disturbances
Purpose of review Forests are frequently exposed to natural disturbances, which are likely to increase with global change, and may jeopardize the delivery of ecosystem services. Mixed-species forests have often been shown to be more productive than monocultures, but it is unclear whether this results from mixed stands being in part more resistant to various biotic and abiotic disturbance factors. This review investigates the relationships between tree diversity and stand resistance to natural disturbances and explores the ecological mechanisms behind the observed relationships. Recent findings Mixed forests appear to be more resistant than monocultures to small mammalian herbivores, soil-borne fungal diseases and specialized insect herbivores. Admixing broadleaves to conifers also increases the resistance to fire and windstorms when compared to pure conifer stands. However, mixed forests may be more affected by drought depending on the species in the mixture. Summary Overall, our findings suggest that mixed forests are more resistant to natural disturbances that are relatively small-scale and selective in their effect. However, benefits provided by mixtures are less evident for larger-scale disturbances. Higher tree diversity translates into increased resistance to disturbances as a result of ecological trait complementarity among species, reduction of fuel and food resources for herbivores, enhancement of diversion or disruption processes, and multi-trophic interactions such as predation or symbiosis. To promote resistance, the selection of tree species with different functional characteristics appears more important than increasing only the number of species in the stand. Trees with different levels of susceptibility to different hazards should be intermixed in order to reduce the amount of exposed resources and to generate barriers against contagion. However, more research is needed to further improve associational resistance in mixed forests, through a better understanding of the most relevant spatial and temporal scales of species interactions and to optimize the overall provision of ecosystem services.
ano.nymous@ccsd.cnrs.fr.invalid (Herve Jactel) 03 Oct 2017
https://hal.science/hal-01608422v1
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[hal-01607165] Atmospheric deposition, CO2, and change in the land carbon sink
Concentrations of atmospheric carbon dioxide (CO2) have continued to increase whereas atmospheric deposition of sulphur and nitrogen has declined in Europe and the USA during recent decades. Using time series of flux observations from 23 forests distributed throughout Europe and the USA, and generalised mixed models, we found that forest-level net ecosystem production and gross primary production have increased by 1% annually from 1995 to 2011. Statistical models indicated that increasing atmospheric CO2 was the most important factor driving the increasing strength of carbon sinks in these forests. We also found that the reduction of sulphur deposition in Europe and the USA lead to higher recovery in ecosystem respiration than in gross primary production, thus limiting the increase of carbon sequestration. By contrast, trends in climate and nitrogen deposition did not significantly contribute to changing carbon fluxes during the studied period. Our findings support the hypothesis of a general CO2-fertilization effect on vegetation growth and suggest that, so far unknown, sulphur deposition plays a significant role in the carbon balance of forests in industrialized regions. Our results show the need to include the effects of changing atmospheric composition, beyond CO2, to assess future dynamics of carbon-climate feedbacks not currently considered in earth system/climate modelling.
ano.nymous@ccsd.cnrs.fr.invalid (M. Fernández-Martínez) 26 May 2020
https://hal.science/hal-01607165v1
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[hal-01584260] The potential benefit of using forest biomass data in addition to carbon and water flux measurements to constrain ecosystem model parameters: Case studies at two temperate forest sites
Biomass as a resource, and as a vulnerable carbon pool, is a key variable to diagnose the impacts of global changes on the terrestrial biosphere, and therefore its proper description in models is crucial. Model-Data Fusion (MDF) or data assimilation methods are useful tools in improving ecosystem models that describe interactions between vegetation and atmosphere. We use a MDF method based on a Bayesian approach, in which data are combined with a process model in order to provide optimized estimates of model parameters and to better quantify model uncertainties, whilst taking into account prior information on the parameters. With this method we are able to use multiple data streams, which allows us to simultaneously constrain modeled variables at site level across different temporal scales. In this study both high frequency eddy covariance flux measurements of net CO2 and evapotranspiration (ET), and low frequency biometric measurements of total aboveground biomass and the annual increment (which includes all compartments), are assimilated with the ORCHIDEE model version "AR5" at a beech (Hesse) and a maritime pine (Le Bray) forest site using four to five years of flux data and nine years of biomass data. When assimilating the observed aboveground annual biomass increment (AGB_inc) together with net CO2 and ET flux, the RMSE of modelled AGBinc was reduced from the a priori estimates by 37% at Hesse and 69% at Le Bray, without reducing the fit to the net CO2 and ET that can be achieved when assimilating flux data alone. Assimilating biomass increment data also provides insight in the performance of the allocation scheme of the model. Comparison with detailed site-based measurements at Hesse showed that the optimization reduced positive biases in the model, for example in fine root and leaf production. We also investigated how to use stand-scale total aboveground biomass in optimization (AGB_tot). However, this study demonstrated that assimilating AGB_tot measurements in the ORCHIDEE-AR5 model lead to some inconsistencies, particularly for the annual dynamics of the AGB_inc, partly because this version of the model lacked a realistic representation of forest stand processes including management and disturbances.
ano.nymous@ccsd.cnrs.fr.invalid (T. Thum) 08 Sep 2017
https://hal.science/hal-01584260v1
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[hal-01595463] Shared genetic predisposition in rheumatoid arthritis-interstitial lung disease and familial pulmonary fibrosis
Despite its high prevalence and mortality, little is known about the pathogenesis of rheumatoid arthritis-associated interstitial lung disease (RA-ILD). Given that familial pulmonary fibrosis (FPF) and RA-ILD frequently share the usual pattern of interstitial pneumonia and common environmental risk factors, we hypothesised that the two diseases might share additional risk factors, including FPF-linked genes. Our aim was to identify coding mutations of FPF-risk genes associated with RA-ILD.We used whole exome sequencing (WES), followed by restricted analysis of a discrete number of FPF-linked genes and performed a burden test to assess the excess number of mutations in RA-ILD patients compared to controls.Among the 101 RA-ILD patients included, 12 (11.9%) had 13 WES-identified heterozygous mutations in the TERT, RTEL1, PARN or SFTPC coding regions. The burden test, based on 81 RA-ILD patients and 1010 controls of European ancestry, revealed an excess of TERT, RTEL1, PARN or SFTPC mutations in RA-ILD patients (OR 3.17, 95% CI 1.53-6.12; p=9.45x10-4). Telomeres were shorter in RA-ILD patients with a TERT, RTEL1 or PARN mutation than in controls (p=2.87x10-2).
ano.nymous@ccsd.cnrs.fr.invalid (Pierre-Antoine Juge) 27 Sep 2017
https://hal.science/hal-01595463v1
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[hal-03008083] Use of microbiological indicators and indices of soil organic matter pools to assess impacts of agricultural practices on soil fertility
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ano.nymous@ccsd.cnrs.fr.invalid (Caroline Petitjean) 16 Nov 2020
https://agroparistech.hal.science/hal-03008083v1
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[hal-03008031] Indicateurs microbiologiques et pools de matières organiques pour évaluer l’impact des pratiques agricoles sur la fertilité des sols
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ano.nymous@ccsd.cnrs.fr.invalid (Caroline Petitjean) 16 Nov 2020
https://agroparistech.hal.science/hal-03008031v1
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[hal-01611445] Plant community structure and nitrogen inputs modulate the climate signal on leaf traits
AimLeaf traits strongly impact biogeochemical cycles in terrestrial ecosystems. Understanding leaf trait variation along environmental gradients is thus essential to improve the representation of vegetation in Earth system models. Our aims were to quantify relationships between leaf traits and climate in permanent grasslands at a biogeographical scale and to test whether these relationships were sensitive to (a) the level of nitrogen inputs and (b) the inclusion of information pertaining to plant community organization.LocationPermanent grasslands throughout France.MethodsWe combined existing datasets on climate, soil, nitrogen inputs (fertilization and deposition), species composition and four traits, namely specific leaf area, leaf dry matter content and leaf nitrogen and phosphorus concentrations, for 15,865 French permanent grasslands. Trait-climate relationships were tested using the following four climatic variables available across 1,833 pixels (5 kmx5 km): mean annual temperature (MAT) and precipitation (MAP), and two indices accounting for the length of the growing season. We compared these relationships at the pixel level using either using community-level or species' trait means.ResultsOur findings were as follows: (a) leaf traits related to plant nutrient economy shift consistently along a gradient of growing season length accounting for temperature and soil water limitations of plant growth (GSL(tw)); (b) weighting leaf traits by species abundance in local communities is pivotal to capture leaf trait-environment relationships correctly at a biogeographical scale; and (c) the relationships between traits and GSL(tw) weaken for grasslands with a high nitrogen input.Main conclusionsThe effects of climate on plant communities are better described using composite descriptors than coarse variables such as MAT or MAP, but appear weaker for high-nitrogen grasslands. Using information at the community level tends to strengthen trait-climate relationships. The interplay of land management, community assembly and bioclimate appears crucial to the prediction of leaf trait variations and their effects on biogeochemical cycles.
ano.nymous@ccsd.cnrs.fr.invalid (Benjamin Borgy) 07 May 2018
https://hal.science/hal-01611445v1
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[hal-02954366] Quelles sources cartographiques pour la définition des usages anciens du sol en France ?
La délimitation de forêts dites anciennes, caractérisées par une longue continuité temporelle de l’état boisé, impose le recours à des sources cartographiques. Quand un tel travail est entrepris sur une vaste surface, l’examen systématique de toute la documentation existante est exclu, et il faut alors définir un unique corpus cartographique qui puisse faire référence sur la totalité du territoire étudié. Deux sources s’imposent alors comme étant les plus adaptées : le cadastre dit napoléonien, et la carte d’état-major, tous deux en général réalisés à une date proche du minimum historique forestier français. Les travaux ici présentés confrontent ces deux sources pour en évaluer les avantages et inconvénients réciproques, non seulement pour la cartographie des forêts anciennes mais aussi, plus largement, pour la construction de la carte de l’ensemble des occupations passées du sol, incluant forêts, pâtures, prairies, cultures, vignes et bâti
ano.nymous@ccsd.cnrs.fr.invalid (Xavier Rochel) 05 Oct 2020
https://hal.science/hal-02954366v1
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[hal-02629172] Continuous soil carbon storage of old permanent pastures in Amazonia
Amazonian forests continuously accumulate carbon (C) in biomass and in soil, representing a carbon sink of 0.42-0.65 GtC yr-1 . In recent decades, more than 15% of Amazonian forests have been converted into pastures, resulting in net C emissions (~200 tC ha-1 ) due to biomass burning and litter mineralization in the first years after deforestation. However, little is known about the capacity of tropical pastures to restore a C sink. Our study shows in French Amazonia that the C storage observed in native forest can be partly restored in old (≥24 year) tropical pastures managed with a low stocking rate (±1 LSU ha-1 ) and without the use of fire since their establishment. A unique combination of a large chronosequence study and eddy covariance measurements showed that pastures stored between -1.27 ± 0.37 and -5.31 ± 2.08 tC ha-1 yr-1 while the nearby native forest stored -3.31 ± 0.44 tC ha-1 yr-1 . This carbon is mainly sequestered in the humus of deep soil layers (20-100 cm), whereas no C storage was observed in the 0- to 20-cm layer. C storage in C4 tropical pasture is associated with the installation and development of C3 species, which increase either the input of N to the ecosystem or the C:N ratio of soil organic matter. Efforts to curb deforestation remain an obvious priority to preserve forest C stocks and biodiversity. However, our results show that if sustainable management is applied in tropical pastures coming from deforestation (avoiding fires and overgrazing, using a grazing rotation plan and a mixture of C3 and C4 species), they can ensure a continuous C storage, thereby adding to the current C sink of Amazonian forests.
ano.nymous@ccsd.cnrs.fr.invalid (Clement Stahl) 17 Aug 2024
https://hal.inrae.fr/hal-02629172v1
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[hal-01559963] Bottom-up and top-down effects of tree species diversity on leaf insect herbivory
The diversity of plant neighbors commonly results in direct, bottom- up effects on herbivore ability to locate their host, and in indirect effects on herbivores involving changes in plant traits and a top-down control by their enemies. Yet, the relative contribution of bottom- up and top-down forces remains poorly understood. We also lack knowledge on the effect of abiotic constraints such as summer drought on the strength and direction of these effects. We measured leaf damage on pedunculate oak (Quercus robur), alone or associated with birch, pine or both in a long-term tree diversity experiment (ORPHEE), where half of the plots were irrigated while the other half remained without irrigation and received only rainfall. We tested three mechanisms likely to explain the effects of oak neighbors on herbivory: (1) Direct bottom-up effects of heterospecific neighbors on oak accessibility to herbivores, (2) indirect bottom-up effects of neighbors on the expression of leaf traits, and (3) top-down control of herbivores by predators. Insect herbivory increased during the growth season but was independent of neighbor identity and irrigation. Specific leaf area, leaf toughness, and thickness varied with neighbor identity while leaf dry matter content or C: N ratio did not. When summarized in a principal component analysis (PCA), neighbor identity explained 87% of variability in leaf traits. PCA axes partially predicted herbivory. Despite greater rates of attack on dummy caterpillars in irrigated plots, avian predation, and insect herbivory remained unrelated. Our study suggests that neighbor identity can indirectly influence insect herbivory in mixed forests by modifying leaf traits. However, we found only partial evidence for these trait―mediated effects and suggest that more attention should be paid to some unmeasured plant traits such as secondary metabolites, including volatile organic compounds, to better anticipate the effects of climate change on plant-insect interactions in the future.
ano.nymous@ccsd.cnrs.fr.invalid (Bastien Castagneyrol) 21 Jun 2018
https://univ-rennes.hal.science/hal-01559963v1
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[hal-02791145] Bottom-up and top-down effects of tree diversity on insect herbivory on pedunculate oak
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ano.nymous@ccsd.cnrs.fr.invalid (Bastien Castagneyrol) 05 Jun 2020
https://hal.inrae.fr/hal-02791145v1
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[hal-02625539] Short- and Long-term influence of litter quality and quantity on simulated heterotrophic soil respiration in a lowland tropical forest
Heterotrophic soil respiration (SRH) alone can contribute up to 50% of total ecosystem respiration in tropical forests. Whereas the abiotic controls of SRH have been extensively studied, the influence of plant traits is less well characterised. We used field experiments and a modelling approach to test the relative influence of plant traits on SRH in lowland tropical forest in French Guiana. We measured leaf- and root litter traits for five common tree species and conducted a root decomposition experiment to evaluate the influence of root chemistry on decay rates. We measured SRH in trenched plots and used our field measurements to parameterize and test the Century model of soil C dynamics. Overall, the Century model performed well in simulating SRH, and species-specific root decomposition in Century corresponded well to decomposition rates measured in situ. Root litter characterized by low lignin-to-nitrogen ratios decomposed more rapidly than low-quality root litter during the first 6 months. Model runs over different time scales revealed that litter quality substantially influenced SRH on an annual time-scale by determining the rates of root- and leaf litter decomposition. However, litter mass had an overriding influence on SRH over the longer term in 20-year model runs. Synthesis Using simple plant trait data to parameterise the Century model, we were able to accurately simulate changes in SRH in a lowland tropical forest. Our results suggest that this approach could be used to predict changes in tropical soil C dynamics under global change scenarios by including data on changes in plant productivity and C inputs to the soil (for example litterfall and root turnover).
ano.nymous@ccsd.cnrs.fr.invalid (Laetitia Brechet) 26 May 2020
https://hal.inrae.fr/hal-02625539v1
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[hal-01607772] Les plantes au rythme des saisons : guide d'observation phénologique
Découvrez dans ce bel ouvrage toutes les informations pour vous initier à l'observation du cycle de vie de la flore qui nous entoure (débourrement des bourgeons au printemps, maturation des fruits en été , coloration des feuilles à l'automne...) et comprendre les enjeux de la science complexe qu'est la phénologie dans le contexte du changement climatique. 79 plantes communes y sont présentées sous la forme de fiches détaillées (identification, écologie et répartition de la plante, calendrier du cycle annuel, différents stades phénologiques), très joliment illustrées de belles aquarelles et de photographies.
ano.nymous@ccsd.cnrs.fr.invalid (Vincent Badeau) 03 Oct 2017
https://hal.science/hal-01607772v1
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[hal-01606884] Sémantique et métadonnées de l'infrastructure AnaEE-france
Sémantique et métadonnées de l'infrastructure AnaEE-france. Forum des utilisateurs de l’e-infrastructure ECOSCOPE - Portail de métadonnées
ano.nymous@ccsd.cnrs.fr.invalid (Christian Pichot) 03 Oct 2017
https://hal.science/hal-01606884v1
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[hal-01594884] Modelling hydraulic functioning of an adult beech stand under non-limiting soil water and severe drought condition
• SPAC model to predict forest water consumption under wet and dry conditions. • Interactions and feedbacks between physical climate and ecological processes. • Control of root water uptake by water diffusion processes between roots and soil. • Key processes involved: xylem hydraulic resistances and stomatal conductance. • Buffering action of capacitive discharge on daily fluctuations of xylem tension. Modelling hydraulic functioning of a forest stand is a prerequisite to predict the future impact of climate change on forests. In this paper, we used a process-based model of the soil-plant-atmosphere continuum to investigate the links between energy budget and water balance, and to emphasize the key processes involved in the control of transpiration and water status of forest trees. The model describes stomatal conductance as a function of photosynthesis, intercellular CO2 concentration and leaf water potential. The latter in turn depends on soil and tree storage water potentials, the water flux through the soil and the trees, hydraulic resistances and stomatal conductance. We have implemented in the model a detailed tree water storage scheme, canopy interception of precipitation, and the rate of change of forest canopy energy storage. In this model, physical climate processes and ecological processes are closely coupled which involves important interactions and feedbacks. The model reproduces the observed variation in leaf water potential in dry and wet conditions. It successfully captures the decrease in soil water content under both non-limiting soil water and severe drought conditions and there is a good agreement between measured and simulated sensible and latent heat fluxes throughout the season. Simulations also show that significant amounts of intercepted water can be lost through evaporation during rain events. The results corroborate that the concept of hydraulic capacitance provides a simple and effective means of simulating the buffering action of tree water storage on tree water status. The two key parameters that control transpiration and water status of the trees are xylem hydraulic resistances and sensitivity of stomata to leaf water potential. The results confirm that stomatal conductance cannot be modelled using leaf-level processes alone, but must be incorporated into a comprehensive model of water flow from soil through the plants to the atmosphere where various self-regulation are set up to ensure a complete water status equilibrium.
ano.nymous@ccsd.cnrs.fr.invalid (Andrée Tuzet) 26 Sep 2017
https://hal.science/hal-01594884v1
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[hal-01465075] Sensitivity of community-level trait-environment relationships to data representativeness: a test for functional biogeography
Aim: The characterization of trait–environment relationships over broad-scale gradients is a critical goal for ecology and biogeography. This implies the merging of plot and trait databases to assess community-level trait-based statistics. Potential shortcomings and limitations of this approach are that: (i) species traits are not measured where the community is sampled and (ii) the availability of trait data varies considerably across species and plots. Here we address the effect of trait data representativeness [the sampling effort per species and per plot] on the accuracy of (i) species-level and (ii) community-level trait estimates and (iii) the consequences for the shape and strength of trait–environment relationships across communities. Innovation: We combined information existing in databases of vegetation plots and plant traits to estimate community-weighted means [CWMs] of four key traits [specific leaf area, plant height, seed mass and leaf nitrogen content per dry mass] in permanent grasslands at a country-wide
ano.nymous@ccsd.cnrs.fr.invalid (Benjamin Borgy) 26 Apr 2018
https://hal.science/hal-01465075v1
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[hal-01608443] Network connectivity value
In order to unveil the value of network connectivity, we formalize the construction of ecological networks in forest environments as an optimal control dynamic graph-theoretic problem. The network is based on a set of bioreserves and patches linked by ecological corridors. The node dynamics, built upon the consensus protocol, form a time evolutive Mahalanobis distance weighted by the opportunity costs of timber production. We consider a case of complete graph, where the ecological network is fully connected, and a case of incomplete graph, where the ecological network is partially connected. The results show that the network equilibrium depends on the size of the reception zone, while the network connectivity depends on the environmental compatibility between the ecological areas. Through shadow prices, we find that securing connectivity in partially connected networks is more expensive than in fully connected networks, but should be undertaken when the opportunity costs are significant.
ano.nymous@ccsd.cnrs.fr.invalid (Arnaud Dragicevic) 03 Oct 2017
https://hal.science/hal-01608443v1
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[hal-01595597] Deer browsing promotes Norway spruce at the expense of silver fir in the forest regeneration phase
Deer populations have dramatically increased over the last decades in Western Europe and their browsing has affected forest vegetation, especially plant community composition. High deer browsing pressure may threaten forest ecosystems and needs to be assessed over the long run. However, few studies to date have addressed the long-term impact of deer on forest regeneration. During one regeneration phase, we assessed the impact of deer (Cervus elaphus L and Capreolus capreolus L) browsing on mixed silver fir (Abies alba Mill.)/Norway spruce (Picea abies L. H. Karst.) stands in the Vosges Mountains in North-eastern France. For both tree species, we measured seedling and sapling density, height and diameter in 28 paired fenced - unfenced plots distributed over two sites that had been fenced 27 years ago, for 10 and 23 years respectively. We demonstrated that the presence of deer decreased the density, height and diameter of silver fir saplings, while it increased the height of Norway spruce saplings. We also noticed that the effect of fencing was very different depending on fencing duration, and that even 10 years of fencing led to changes that were still visible 17 years later. Our results confirm that deer browsing has a long-term impact on the regeneration of silver fir. Furthermore, they suggest that deer browsing may cause a species substitution, with Norway spruce gradually replacing silver fir. Such a trend would have an impact on the ecological and economical value of these forests. How browsing impacts the forest's ability to adapt to global warming should also be considered, since browsing might impede the implementation of management policies designed to address this issue.
ano.nymous@ccsd.cnrs.fr.invalid (Marianne Bernard) 27 Sep 2017
https://hal.science/hal-01595597v1
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[hal-02998652] Combined Effects of Ozone and Drought on the Physiology and Membrane Lipids of Two Cowpea (Vigna unguiculata (L.) Walp) Cultivars
The interactive effects of drought and ozone on the physiology and leaf membrane lipid content, composition and metabolism of cowpea (Vigna unguiculata (L.) Walp.) were investigated in two cultivars (EPACE-1 and IT83-D) grown under controlled conditions. The drought treatment (three-week water deprivation) did not cause leaf injury but restricted growth through stomatal closure. In contrast, the short-term ozone treatment (130 ppb 12 h daily during 14 day) had a limited impact at the whole-plant level but caused leaf injury, hydrogen peroxide accumulation and galactolipid degradation. These effects were stronger in the IT83-D cultivar, which also showed specific ozone responses such as a higher digalactosyl-diacylglycerol (DGDG):monogalactosyldiacylglycerol (MGDG) ratio and the coordinated up-regulation of DGDG synthase (VuDGD2) and ω-3 fatty acid desaturase 8 (VuFAD8) genes, suggesting that membrane remodeling occurred under ozone stress in the sensitive cultivar. When stresses were combined, ozone did not modify the stomatal response to drought and the observed effects on whole-plant physiology were essentially the same as when drought was applied alone. Conversely, the drought-induced stomatal closure appeared to alleviate ozone effects through the reduction of ozone uptake.
ano.nymous@ccsd.cnrs.fr.invalid (Deborah Moura Rebouças) 10 Nov 2020
https://hal.univ-lorraine.fr/hal-02998652v1
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[hal-02618498] Le programme ANR Agrobiosphère : l'importance d'une programmation thématique pour l'émergence de nouveaux concepts
Le programme Agrobiosphère de l'ANR (2011-2013) visait à étudier les transitions vers des systèmes productifs durables dans un contexte de changement global. Il faisait suite aux programmes ADD (2005-2006) et Systerra (2008-2010) ainsi qu'à l'atelier de réflexion prospective Adage, sur les impacts du changement climatique et les nouvelles stratégies d'adaptation. Il affichait comme prioritaires les questions relatives aux trajectoires d'évolution à long terme des systèmes, à la conception des innovations agroécologiques aux niveaux des territoires et des filières, en interrogeant également les notions de transition, de viabilité et de résilience dans des situations de changement. Nous présentons ici les faits marquants du colloque bilan de ce programme, organisé en novembre 2016, au cours duquel les résultats obtenus par les projets ont été discutés autour de cinq thèmes émergents : adaptation aux changements globaux ; cycles biogéochimiques ; biodiversité fonctionnelle ; modélisation territoriale et accompagnement des acteurs ; relations milieux-systèmes économiques. Ce bilan du programme Agrobiosphère montre que celui-ci a facilité la construction de nouvelles formes de collaborations interdisciplinaires et interinstitutionnelles et a entraîné une participation accrue, par rapport aux programmes précédents, des équipes en écologie et en sciences sociales aux projets, ouvrant ainsi l'espace des recherches agronomiques aux différentes dimensions du développement durable. Il a été fondamental pour approfondir le concept d'agroécologie. L'expérience du programme Agrobiosphère montre l'importance de la programmation thématique pour soutenir une recherche orientée et finalisée.
ano.nymous@ccsd.cnrs.fr.invalid (Bernard Hubert) 25 May 2020
https://hal.inrae.fr/hal-02618498v1
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[hal-01609984] Physical Root-Soil Interactions
Plant root system development is highly modulated by the physical properties of the soil and especially by its mechanical resistance to penetration. The interplay between the mechanical stresses exerted by the soil and root growth is of particular interest for many communities, in agronomy and soil science as well as in biomechanics and plant morphogenesis. In contrast to aerial organs, roots apices must exert a growth pressure to penetrate strong soils and reorient their growth trajectory to cope with obstacles like stones or hardpans or to follow the tortuous paths of the soil porosity. In this review, we present the main macroscopic investigations of soil-root physical interactions in the field and combine them with simple mechanistic modeling derived from model experiments at the scale of the individual root apex.
ano.nymous@ccsd.cnrs.fr.invalid (Evelyne Kolb) 04 Oct 2017
https://uca.hal.science/hal-01609984v1
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[hal-01530800] X-ray computed tomography to decipher the genetic architecture of tree branching traits: oak as a case study
A new method for obtaining internal views of tree trunks was recently developed using X-ray computed tomography (CT). This technology makes it possible to observe and measure rameal traces that are left by latent buds, sequential branches, and epicormic branches in the wood. Epicormic branches are undesirable for producing high-value solid wood, especially in Quercus robur, an important hardwood forest tree species in Europe, which is prone to epicormic branches that develop from abundant latent buds. For the very first time, branching-related traits deduced from X-ray CT observation make it possible to analyze the genetic architecture of oak branching through a quantitative trait locus (QTL) analysis. Highly significant QTLs were detected for traits related to latent buds and epicormic branches. The number and effect of these QTLs suggest a moderate genetic determinism for the formation of latent buds and the development of epicormic branches. Three hotspots were found, grouping QTLs for different branching traits. An analysis of the common physiological denominators of these coincident traits suggests that their genetic controls are related to either the regulation of the axillary meristem initiation or to bud dormancy. Conversely, the position of only the separate QTL related to the number of sequential branches suggests an independent genetic control.
ano.nymous@ccsd.cnrs.fr.invalid (Jialin Song) 31 May 2017
https://hal.science/hal-01530800v1
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[hal-01567220] Increased light-use efficiency sustains net primary productivity of shaded coffee plants in agroforestry system
In agroforestry systems, shade trees strongly affect the physiology of the undergrown crop. However, a major paradigm is that the reduction in absorbed photosynthetically active radiation is, to a certain extent, compensated by an increase in light-use efficiency, thereby reducing the difference in net primary productivity between shaded and non-shaded plants. Due to the large spatial heterogeneity in agroforestry systems and the lack of appropriate tools, the combined effects of such variables have seldom been analysed, even though they may help understand physiological processes underlying yield dynamics. In this study, we monitored net primary productivity, during two years, on scales ranging from individual coffee plants to the entire plot. Absorbed radiation was mapped with a 3D model (MAESPA). Light-use efficiency and net assimilation rate were derived for each coffee plant individually. We found that although irradiance was reduced by 60% below crowns of shade trees, coffee light-use efficiency increased by 50%, leaving net primary productivity fairly stable across all shade levels. Variability of aboveground net primary productivity of coffee plants was caused primarily by the age of the plants and by intraspecific competition among them (drivers usually overlooked in the agroforestry literature) rather than by the presence of shade trees.
ano.nymous@ccsd.cnrs.fr.invalid (Fabien Charbonnier) 21 Jul 2017
https://hal.science/hal-01567220v1
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[hal-01901340] Fish farming in multispecies system: an opportunity to develop a more efficient aquaculture
Fish farming in multispecies system: an opportunity to develop a more efficient aquaculture. Aquaculture Europe 2017
ano.nymous@ccsd.cnrs.fr.invalid (M. Thomas) 22 Oct 2018
https://hal.science/hal-01901340v1
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[hal-02791351] Exposition "Les Plantes au rythme des saisons
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ano.nymous@ccsd.cnrs.fr.invalid (Vincent Badeau) 05 Jun 2020
https://hal.inrae.fr/hal-02791351v1
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[hal-01360339] Bias correction of dynamically downscaled precipitation to compute soil water deficit for explaining year-to-year variation of tree growth over northeastern France.
This paper documents the accuracy of a post-correction method applied to precipitation regionalized by the Weather Research and Forecasting (WRF) Regional Climate Model (RCM) for improving simulated rainfall and feeding impact studies. The WRF simulation covers Burgundy (northeastern France) at a 8-km resolution and over a 20-year long period (1989–2008). Previous results show a strong deficiency of the WRF model for simulating precipitation, especially when convective processes are involved. In order to reduce such biases, a Quantile Mapping (QM) method is applied to WRF-simulated precipitation using the mesoscale atmospheric analyses system SAFRAN («Système d'Analyse Fournissant des Renseignements Adaptés à la Nivologie») that provides precipitation data at an 8 km resolution. Raw and post-corrected model outputs are next used to compute the soil water balance of 30 Douglas-fir and 57 common Beech stands across Burgundy, for which radial growth data are available. Results show that the QM method succeeds at reducing the model's wet biases in spring and summer. Significant improvements are also noted for rainfall seasonality and interannual variability, as well as its spatial distribution. Based on both raw and post-corrected rainfall time series, a Soil Water Deficit Index (SWDI) is next computed as the sum of the daily deviations between the relative extractible water and a critical value of 40% below which the low soil water content induce stomatal regulation. Post-correcting WRF precipitation does not significantly improve the simulation of the SWDI upon the raw (uncorrected) model outputs. Two characteristic years were diagnosed to explain this unexpected lack of improvement. Although the QM method allows producing realistic precipitation amounts, it does not correct the timing errors produced by the climate model, which is yet a major issue to obtain reliable estimators of local-scale bioclimatic conditions for impact studies. A realistic temporality of simulated precipitation is thus required before using any systematic post-correction method for appropriate climate impact assessment over temperate forests.
ano.nymous@ccsd.cnrs.fr.invalid (Damien Boulard) 27 Sep 2017
https://hal.science/hal-01360339v1
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[hal-01563605] Nitrogen dynamics in a nutrient-poor soil under mixed-species plantations of eucalypts and acacias
Introducing nitrogen-fixing species (NFS) in eucalypt plantations is a useful practice to compensate nitrogen loss at harvest, reduce fertilizer inputs, improve soil fertility and sustain forest productivity in low input systems. Nitrogen (N) and carbon (C) were evaluated in the active part of soil organic matter (SOM) i.e., the particulate organic matter (POM), which was obtained after soil (0-0.05 m) physical fractionation at the end of a first 7-year rotation (R1Y7) and at year 2 of a second rotation (R2Y2) in pure acacia (100A), pure eucalypt (100E) and mixed-species (50A50E) stands in an experimental plantation established on an Arenosol in the Congolese coastal plains. N concentration (in g kg(-1) of soil) was higher in coarse POM (cPOM, 4000-250 mu m) in 100A and 50A50E compared to 100E at 2YR2, while no difference was found in fine POM (fPOM, 250-50 gm) and in the organo-mineral fraction (OMF, < 50 mu m). N content in cPOM was more than 3 times higher at R2Y2 than at R1Y7. A slight increase was also observed in fPOM, while no difference was observed in OMF between R1Y7 and R2Y2. Lower C:N ratios in the two POM fractions in 100A and, to a lesser extent, in 50A50E compared to 100E suggests an improved soil N status after acacia trees have been introduced in eucalypt plantations. The lack of difference in N content of coarse POM between 100A and 50A50E at R1Y7, despite higher amount of N in the forest floor and N returning to the soil (harvest residues and litterfall) in 100A than in 50A50E, suggests a faster cycling of nitrogen under acacia than under eucalypt.
ano.nymous@ccsd.cnrs.fr.invalid (Lydie-Stella Koutika) 17 Jul 2017
https://hal.science/hal-01563605v1
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[hal-01644046] Biomass production, nitrogen accumulation and symbiotic nitrogen fixation in a mixed-species plantation of eucalypt and acacia on a nutrient-poor tropical soil
The success of mixed-species tree plantations depends on the balance between positive and negative interactions. Mixtures of Acacia mangium and Eucalyptus urophylla x grandis out-yield their respective monocultures in term of wood production on the Congolese coastal plain, suggesting that facilitation and/or competitive reduction surpass interspecific competition. We investigated how these interactions affected biomass production and N accumulation during the early growth stage of a second rotation of a mixed-species stand of these two species. We used the N-15 dilution method to estimate symbiotic nitrogen fixation and its contribution to N accumulation in acacia monoculture and mixture, and we assessed how much N derived from the atmosphere is transferred to the eucalypt trees in the mixed-species stand. Eucalypts grew taller and acacias grew larger in the mixture compared to the monocultures. N mineralomass was greater in the mixture relative to the average values in the two monocultures, with both species contributing to this enhanced N mineralomass. The amount of N derived from the atmosphere in the mixture was 60% higher than that expected given the amount found in acacia monoculture, and 16% of the nitrogen accumulated in eucalypt trees and aboveground eucalypt litterfall was derived from the atmosphere. Reduced competition for light and soil water also contributed to the increased growth of acacias in the mixture, showing that both species benefit from growing in a mixed stand.
ano.nymous@ccsd.cnrs.fr.invalid (Sogni-Viviane Tchichelle) 21 Nov 2017
https://hal.science/hal-01644046v1
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[hal-01607594] Seasonality of nitrogen partitioning (non-structural vs structural) in the leaves and woody tissues of tropical eucalypts experiencing a marked dry season
Numerous studies have shown that internal nitrogen (N) translocation in temperate tree species is governed by photoperiod duration and temperature. For tropical tree species, the seasonality of rainfall is known to affect growth and foliage production, suggesting that efficient internal N recycling also occurs throughout the year. We tested this hypothesis by comparing the N budgets and N partitioning (non-structural vs structural N) in the different organs of 7-year-old Eucalyptus urophylla (S.T. Blake) x E. grandis (W. Hill ex Maiden) trees from a plantation in coastal Congo on poor sandy soil. The trees were sampled at the end of the dry season and late in the rainy season. Lower N concentrations and N investment in the non-structural fraction were observed in leaves during the dry season, which indicates resorption of non-structural N from senescing leaves. Stem wood, which contributes to about 60% of the total biomass of the trees, accumulated high amounts of non-structural N at the end of the dry season, most of which was remobilized during the following rainy season. These results support the hypothesis of efficient internal N recycling, which may be an important determinant for the growth potential of eucalypts on N-poor soils. Harvesting trees late in the rainy season when stem wood is depleted in non-structural N should be recommended to limit the export of nutrients off-site and to improve the sustainability of tropical eucalypt plantations.
ano.nymous@ccsd.cnrs.fr.invalid (Dominique Gerant) 03 Oct 2017
https://hal.science/hal-01607594v1
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[hal-02784974] A hydraulic perspective on the interspecific diversity of drought resistance strategies in coexisting tropical rainforest tree species of French Guiana
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ano.nymous@ccsd.cnrs.fr.invalid (Camille Ziegler) 05 Jun 2020
https://hal.inrae.fr/hal-02784974v1
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[hal-01604940] Fine-scale species distribution changes in a mixed oak stand over two successive generations
Large-scale tree distribution changes have received considerable attention but underlying demo-genetic mechanisms are less well documented. We used a diachronic approach to track species shifts in a mixed oak stand (Quercus petraea-Quercus robur) at a fine spatiotemporal scale. Species assignment was made using single nucleotide polymorphism (SNP) fingerprints employing clustering and parentage analysis. Mating patterns and reproductive success were assessed by parentage analysis. Plot-based inventories of soil parameters and sapling densities provided ecological and demographic information, respectively. Sapling density and reproductive success was higher in Q. petraea than in Q. robur, and were correlated with a spatial expansion of Q. petraea (50% to 67% of the area). Admixed trees resulting from hybridization and backcrossing between the two species were more frequent under the Q. robur canopy. We suspect that species' differential responses to ongoing environmental changes and interspecific competition are the predominant factors accounting for the recruitment success of Q. petraea, while human interference, differential reproduction and hybridization (and backcrossings) are probably of more limited importance. We anticipate in mixed Q. petraea-Q. robur stands, under current ongoing environmental change, that these processes will be enhanced, at least in the western part of the distribution of the two species.
ano.nymous@ccsd.cnrs.fr.invalid (Laura Truffaut) 10 Apr 2025
https://hal.science/hal-01604940v1
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[hal-02786594] Genetic architecture of water use efficiency across two oak species and their hybrids
[...]
ano.nymous@ccsd.cnrs.fr.invalid (Oliver Brendel) 05 Jun 2020
https://hal.inrae.fr/hal-02786594v1
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[hal-03484016] Large Variation in Carbon Isotope Composition of Bulk Leaf Material of Rubber Trees from a Germplasm Collection: An Opportunity for Improving Water Use Efficiency in Breeding Programs
The rubber tree (Hevea brasiliensis) is an important economic crop, particularly in Thailand. As the plantations extend to new and drier areas, information on physiological parameters such as water use efficiency (WUE) is required to help breeding for adapted genotypes. Carbon isotope composition of bulk leaf (δ13C) can be used as an indicator of intrinsic water use efficiency (WUE) of plants. A prerequisite step is to analyse the genetic variability of δ13C. We compared the carbon isotope composition of bulk rubber tree leaf (δ13C) in rainy and dry seasons in a collection of 49 wild genotypes of rubber in Northern Thailand. There were large δ13C variations among the genotypes at all seasons. δ13C ranged between −33.3‰ to −30.0‰ in rainy season and −33.1‰ to −29.9‰ in dry season. δ13C was rather stable with a good correlation between rainy and dry season. In rainy season, there was a positive significant correlation between δ13C, leaf mass per area (LMA) and leaf nitrogen per area (NA). The average δ13C was significantly different between two genetic clusters previously identified in this population. The large genetic variability of δ13C in wild rubber population is promising for breeding genotypes using less water.
ano.nymous@ccsd.cnrs.fr.invalid (N. Kanpanon) 16 Dec 2021
https://hal.inrae.fr/hal-03484016v1
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[hal-03615658] Historical ecology of lowland forests: Does pedoanthracology support historical and archaeological data?
Historical ecology is a cross-disciplinary approach which uses various sources to reconstruct past ecosystems and landscapes, and their interactions with human activities. Here we assess the potential contribution of soil charcoal analysis to the understanding of the dynamics of forest-human relationships in a temperate deciduous forest of North France since the Roman times. We conducted a soil charcoal analysis in three contrasted forest stands and soil types (podzol, cambisol and luvisol) using two sampling techniques (pit and auger), and subsequently compared the results to archaeological and historical data, including LiDAR imagery. We show that (i) combining two sampling techniques can more readily reflect the local charcoal assemblages than the traditional pit sampling alone; (ii) the vertical distribution of charcoals cannot be taken as a surrogate for temporal vegetation changes, as a probable consequence of biological mixing among soil horizons; (iii) once dated, soil charcoal assemblages provide support to an early medieval forest colonisation of formerly cultivated sites, the subsequent maintenance of open-canopy forests until the 18th century, and a recent canopy closure. We conclude that pedoanthracology solely cannot solve the question of forest vegetation changes over time, but can provide support to hypotheses made from other approaches such as field archaeological surveys. (C) 2016 Published by Elsevier Ltd.
ano.nymous@ccsd.cnrs.fr.invalid (Thomas Feiss) 21 Mar 2022
https://u-picardie.hal.science/hal-03615658v1
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[hal-02789169] The global distribution of leaf chlorophyll content and seasonal controls on carbon uptake
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ano.nymous@ccsd.cnrs.fr.invalid (Holly Croft) 05 Jun 2020
https://hal.inrae.fr/hal-02789169v1
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[hal-01842097] Modelling hydraulic functioning of a forest stand to simulate drought stress
A model that couples stomatal conductance, photosynthesis, leaf energy balance and transport of water through the soil-tree-atmosphere continuum have been developed (Tuzet et al, 2017). The aim of this study is to develop a general process model to describe the dynamics of the water flow within the continuum and to better understand the relative importance of atmospheric demand, soil water availability and hydraulic controls on tree water use. In this model, stomatal conductance depends on light, temperature and intercellular CO2 concentration via photosynthesis and on leaf water potential. Leaf water potential is a function of soil water potential, tree hydraulic resistances and the rate of water flow through the soil and tree. The net canopy photosynthesis is calculated using the detailed biochemical model of photosynthesis proposed by Farquhar et al. (1980). Tree water relations are modelled as an analogue to a simple electrical circuit including plant hydraulic resistances and plant capacitances. Water uptake by roots is controlled by water potential gradient between the absorbing root surface and a cylindrical soil element adjacent to the roots. Water transport from soil to roots is simulated through solution of the Richards’ equation. Rainfall interception is calculated using an approach derived from the Liu model (Liu, 1997, Liu 2001).Our results show that early in the season when soil moisture is not limiting, minimum leaf water potential remains almost constant. Later, as soil drying proceeds there is a progressive decrease of minimum leaf water potential. This decrease occurs when the limitation of the water transfer imposed by the soil becomes dominant compared to that of the xylem. The minimum values of water potential reached by the leaves depend on the sensitivity of stomata to leaf water potential. The xylem hydraulic resistance determines the amplitude of diurnal variation of the water potentials when soil moisture is not limiting while the sensitivity of stomata to leaf water potential determines the lower limit of potential reached by the leaves when the soil dries. Then our model is able to explain the contrasting behaviour of many functional types of trees in terms of differing hydraulic resistances and stomatal sensitivities of stomata to leaf water potential. ‘Isohydric’ trees, which maintain constant minimum leaf water potentials, are expected have high xylem hydraulic resistances and/or high stomatal sensitivity to leaf water potential. ‘Anisohydric’ trees, which have variable minimum leaf water potentials, are expected to have lower hydraulic resistances and/or lower stomatal sensitivity to leaf water potential.The model reproduces well the commonly observed diurnal variation in transpiration, storage water potentials and capacitive discharge or recharge fluxes under both dry and wet conditions in a stand of European beech. It is able to capture the decrease of relative water content in reservoirs under water stress conditions and their contribution in the transpiration stream, both daily and throughout the season. Depletion of internal water reservoirs delays the onset of stomatal closure in the morning and also limits and regulates the stomatal closure in the afternoon when the climatic demand is high. Trees lose stored water during the day and recover it at night. The presence of reservoirs allows trees to better withstand periods of drought. The model accurately reproduces the seasonal variations of soil water content and leaf water potential. These results are in agreement with those of the comparison between measured and calculated water fluxes. Physical climate processes and ecological processes are closely coupled in the model, which involves important interactions and feedbacks. Capacitive discharge of water into the transpiration stream can buffer fluctuations in xylem tension, thereby diminishing the risk of xylem embolism and hydraulic failure under dynamic conditions. The key conclusion of the paper is that stomatal conductance cannot be modelled using leaf-level processes alone, but must be incorporated into a comprehensive model of water flow from soil through the plants to the atmosphere where various self-regulation are set up to ensure a complete water status equilibrium.
ano.nymous@ccsd.cnrs.fr.invalid (Andree Tuzet) 17 Jul 2018
https://hal.science/hal-01842097v1
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[hal-01559483] Scaling leaf respiration with nitrogen and phosphorus in tropical forests across two continents
Leaf dark respiration (R-dark) represents an important component controlling the carbon balance in tropical forests. Here, we test how nitrogen (N) and phosphorus (P) affect R-dark and its relationship with photosynthesis using three widely separated tropical forests which differ in soil fertility. R-dark was measured on 431 rainforest canopy trees, from 182 species, in French Guiana, Peru and Australia. The variation in R-dark was examined in relation to leaf N and P content, leaf structure and maximum photosynthetic rates at ambient and saturating atmospheric CO2 concentration. We found that the site with the lowest fertility (French Guiana) exhibited greater rates of R-dark per unit leaf N, P and photosynthesis. The data from Australia, for which there were no phylogenetic overlaps with the samples from the South American sites, yielded the most distinct relationships of R-dark with the measured leaf traits. Our data indicate that no single universal scaling relationship accounts for variation in R-dark across this large biogeographical space. Variability between sites in the absolute rates of R-dark and the R-dark : photosynthesis ratio were driven by variations in N- and P-use efficiency, which were related to both taxonomic and environmental variability.
ano.nymous@ccsd.cnrs.fr.invalid (Lucy Rowland) 10 Jul 2017
https://hal.univ-lorraine.fr/hal-01559483v1
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[hal-01525878] Improving identification of coppiced and seeded trees in past woodland management by comparing growth and wood anatomy of living sessile oaks ( Quercus petraea )
Written sources and archaeological evidence suggest that coppicing was a common practice in past woodland management. Depending mainly on the length of rotations, coppices provided wood products of various sizes, and coppice-wood has been identified in fuel-wood remains as well as in timber studies. Assigning the origin of the wood analyzed to coppice is based on observation of “typical growth patterns”: an even-age structure and a rapid decrease in ring-width with age are used nowadays. However, the wide variety of coppice practices and the variability observed in living-tree analogs make it difficult to draw definitive conclusions. To contribute to improving coppice-wood identification, the present study analyzed differences in growth and tree-ring anatomy between living sessile oaks from a mixed stand of coppiced and seeded trees. Stems were compared based on ring-width, early- and late-wood widths, number and size of the earlywood vessels, and tissue proportions measured at different heights. The growth of coppiced trees was found to be faster than that of seeded trees, in height at cambial ages between 3 and 5 years and in diameter at 5–8 years. A quantitative anatomy study showed that tree rings from coppice shoots had smaller and more numerous vessels per unit surface area and a weaker hydraulic conductivity. Earlywood width, which can be acquired on archaeological wood much more easily than vessel surface, was significantly greater in the sample of seeded trees. Linear discriminant analysis performed on the data used to model earlywood width (leave-one-out procedure) correctly classified 77% of coppice and 54% of seeded trees when the radius exceeded 1.66 cm and offers promising perspectives for dendro-anthracology and dendrochronology. Growth and anatomical differences between coppiced and seeded trees mixed in the same stand were observed while other sources of variability (site condition, competition, species) were constrained.
ano.nymous@ccsd.cnrs.fr.invalid (Olivier Girardclos) 17 Nov 2017
https://hal.science/hal-01525878v1
