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Leaf area is a key structural characteristic of forest canopies because of the role of leaves in controlling many biological and physical processes occurring at the biosphere-atmosphere transition. High pulse density Airborne Laser Scanning (ALS) holds promise to provide spatially resolved and accurate estimates of plant area density (PAD) in forested landscapes, a key step in understanding forest functioning: phenology, carbon uptake, transpiration, radiative balance etc. Inconsistencies between different ALS sensors is a barrier to generating globally harmonised PAD estimates. The basic assumption on which PAD estimation is based is that light attenuation is proportional to vegetation area density. This study shows that the recorded extinction strongly depends on target detectability which is influenced by laser characteristics (power, sensitivity, wavelength). Three different airborne laser scanners were flown over a wet tropical forest at the Paracou research station in French Guiana. Different sensors, flight heights and transmitted power levels were compared. Light attenuation was retrieved with an open source ray-tracing code (http://amapvox.org). Direct comparison revealed marked differences (up-to 25% difference in profile-averaged light attenuation rate and 50% difference at particular heights) that could only be explained by differences in scanner characteristics. We show how bias which may occur under various acquisition conditions can generally be mitigated by a sensor intercalibration. Alignment of light weight lidar attenuation profiles to ALS reference attenuation profiles is not always satisfactory and we discuss what are the likely sources of discrepancies. Neglecting the dependency of apparent light attenuation on scanner properties may lead to biases in estimated vegetation density commensurate to those affecting light attenuation estimates. Applying intercalibration procedures supports estimation of plant area density independent of acquisition characteristics.

Dans la zone de Botambi (forêt classée), située au sud-ouest de Bangui, capitale de Centrafrique, la déforestation liée à la pratique de l'agriculture itinérante sur brûlis entraine depuis quelques années le recul de la couverture forestière au profit des jachères pauvres à Chromolaena odorata et des savanes herbeuses. Cette disparition de la forêt est un manque à gagner pour les communautés autochtones et locales qui vivent et dépendent très significativement des ressources issues de la forêt. C'est également une perte pour la nation qui tire une part importante de ses revenus de l'exploitation du bois et pour l'ensemble de l'humanité (protection contre l'érosion des sols, préservation de la biodiversité, séquestration du carbone, etc.). Devant une telle situation, le PDRSO (Projet de Développement Régional du Sud-Ouest) a initié différentes techniques agroforestières dans les villages de Talo, de Botéké et de Salanga, où différents gradients de déforestation et de dégradation peuvent être observés. Ainsi, à Botéké et à Salanga, le projet a procédé à une expérimentation de la technique agroforestière de Régénération Naturelle Assistée durant les sarclages des champs (RNA sarclage ou RNAs). L'avantage de la RNAs est qu'elle permet une régénération rapide lorsque les rejets, semis et/ou drageons des espèces arborées forestières sont épargnés par les agriculteurs lors des activités de sarclage des champs. Le but de cette étude consiste à caractériser la ressource arborée dans les champs traités par la RNA sarclage et de la comparer à celle des champs témoins dans les villages de Talo, de Botéké et de Salanga. Pour atteindre cet objectif, plusieurs campagnes de sensibilisations ont été menées afin d'amener les agriculteurs de Botéké et de Salanga à appliquer cette technique. Au total, 11 agriculteurs de Botéké et 11 de Salanga ont adhéré à la technique et la RNAs a été ainsi installée dans leurs champs dès juin 2019. Les résultats des inventaires floristiques réalisés de juin 2019 à juin 2021 au sein des parcelles agricoles traitées par la RNAs montrent une nette augmentation du nombre d'individus ligneux au cours du temps et par rapport aux témoins. Sur les parcelles avec RNAs, la densité est passée de 177 arbres/ha en juin 2019 à 392 arbres/ha en juin 2021. Au sein des parcelles témoins, une augmentation de la densité des ligneux a été observé mais celle-ci reste très faible par rapport aux parcelles RNA sarclage. Elle est de 97 arbres/ha en juillet 2020 puis de 131 arbres/ha en juin 2021. L'analyse des traits de vie des espèces au sein des parcelles RNAs met en évidence une dominance des mégaphérophytes (58%), un mode de dissémination dominé par des espèces zoochores (75%), un tempérament caractérisé par des espèces pionnières (65%) et une distribution phytogéographique dominée par les espèces à large distribution (58%). Cette même tendance a été observée également au sein des parcelles témoins et a permis de tirer comme conclusion une nette transformation ou conversion de la forêt en jachères pauvres (Botéké) et en savanes herbeuses (Talo). L'analyse de la cinétique de végétation des villages de Botéké et Salanga montre que les parcelles RNAs de Salanga se trouvant en milieu forestier, peu ou pas dégradé, offrent plus de diversité contrairement à celles de Botéké situées dans un milieu forestier dégradé et dans des jachères pauvres. Par ailleurs, cette étude vise à comprendre les pratiques culturales exercées par les agriculteurs. L'objectif étant de savoir si celles-ci permettent une résilience des ligneux et une diffusion à grande échelle de la technique de RNAs pour obtenir ce résultat. Pour mener à bien cette partie, une enquête a été réalisée auprès des agriculteurs des villages de Talo, de Botéké et de Salanga. Concernant les pratiques culturales des agriculteurs dans les trois villages, celles-ci sont restées ancestrales et ne permettent plus à la forêt de se reconstituer. Les défrichements suivis obligatoirement du brûlis, les sarclages des champs sans tenir compte des rejets, semis et/ou drageons et l'implication de la main d'oeuvre salariée durant les défrichements et sarclages entrainent la perte de la couverture forestière dans la zone forestière de Botambi. La technique RNAs expérimentée par le PDRSO est une alternative qui a été appréciée par les agriculteurs qui l'ont expérimenté pour sa simplicité et sa capacité à enrichir les jachères en ligneux utiles). Cependant, seuls les détenteurs de droits fonciers se déclarent prêts à l'utiliser. Pour cette dernière catégorie, la RNAs peut être vulgarisée auprès des agriculteurs, pour une gestion durable des territoires forestiers en République Centrafricaine.

L’étude a porté sur la caractérisation du peuplement ligneux de deux systèmes d’utilisation des terres (la forêt qui est une mise en défens et les champs) dans le terroir de Ngouye au Sénégal. Elle a été effectuée dans une zone agropastorale qui accueille annuellement plusieurs familles de transhumants. Au moyen d’un échantillonnage par relevés de la végétation ligneuse et d’enquêtes auprès des populations nous avons inventorié 28 espèces appartenant à 25 genres et 15 familles botaniques. Les Fabaceae (sous-familles : Mimosoideae, Caesalpinioideae, Faboideae) ont été les plus représentées, suivies des Combretaceae. Les paramètres de l’étude ont révélé qu’il existait des différences nettes entre les deux systèmes, ce qui montrait leur hétérogénéité, avec par ailleurs une grande stabilité de peuplement en forêt. Le peuplement était généralement très jeune, avec un grand pourcentage d’individus dans la première catégorie de diamètreet de hauteur. Les champs avaient la plus forte proportion d’individus adultes mais le taux de régénération dans cette zone était inférieur à celui de la forêt. La richesse spécifique des champs était bien supérieure à celle de la forêt. Sur le plan pastoral les ligneux intervenaient dans l’alimentation du bétail.

Recent climatic events have led to a new municipal commitment: the Tree Plan. It breaks down into five actions, the objective of which is to achieve by 2026 the constitution of a tree-lined grid with the planting of 10,000 trees by the five means proposed. At the same time, the city is deploying means to fight against the rook, present in very large numbers on the territory of Valence and causing nuisance. This thesis examines the feasibility of a peri-urban forest and whether it can be a lasting response to the rook raven problem. A survey of several French towns was carried out in order to find out their approach to their own peri-urban forest and whether they also encountered poultry problems. Then the technical work on the peri-urban forest began. The study of urban planning documents and a forecast of the plots made it possible to geographically locate the future forest belts. Then a work of gathering knowledge on the way of life of the raven made it possible to know its needs in terms of living environment. It was therefore possible to provide, using forestry techniques, a proposal for the development of new living areas and to integrate them into the peri-urban forest.; Les évènements climatiques récents ont conduit vers un nouvel engagement municipal : le Plan Arbre. Il se décompose en cinq actions dont l’objectif est d’atteindre pour 2026 la constitution d’une trame arborée avec la plantation de 10 000 arbres par les cinq moyens proposés. En parallèle, la ville déploie des moyens de lutte contre le corbeau freux, présent en très grand nombre sur le territoire valentinois et causeur de nuisances. Ce mémoire s’interroge sur la faisabilité d’une forêt périurbaine et si elle peut être une réponse pérenne au problème du corbeau freux. Une enquête auprès de plusieurs villes françaises a été menée afin de connaître leur approche sur leur propre forêt périurbaine et si elles rencontraient également des problèmes avicoles. Ensuite, le travail technique concernant la forêt périurbaine a commencé. L’étude des documents d’urbanisme et une prospective des parcelles a permis de situer géographiquement les futures ceintures forestières. Puis un travail de rassemblement de connaissances sur le mode de vie du corbeau a permis de connaître ses besoins en terme de cadre de vie. Il a donc été possible d’apporter grâce à des techniques forestières, une proposition d’aménagement de nouvelles zones de vie et de les intégrer à la forêt périurbaine.

The development of a sustainable wood energy chain is an essential part of ecological and energy transition in Reunion Island (Indian Ocean), where Acacia mearnsii is the main potential wood energy resource identified to date. In order to assess future wood biomass supply chain strategies, a major first issue is to gain knowledge of the spatial distribution of this species forest stands.In this study, we assessed the potential of very high spatial resolution multispectral imagery for mapping the main forest stands in a study area located the Western Highlands region, where Acacia mearnsii expands alongside Acacia heterophylla, an endemic forest species and Cryptomeria japonica, an exotic forest stand. A reference database including 150 samples of seven classes (Acacia mearnsii (mature and non-mature), Acacia heterophylla (mature and non-mature), Cryptomeria japonica, ‘herbaceous areas’, and ‘bare soils’) was used to classify a Pleiades image acquired in May 2020. Spectral and textural indices were used in an incremental classification procedure using a random classifier.The best results (Kappa = 0.84, global accuracy = 84%) were obtained for the classification using all spectral and textural bands. The resulting map enables analyzing the spatial distribution of the different forest stands.

International audience; Savanna is one of the main African ecosystems. The tree community in the savanna is a key element and provides many ecosystem services. Unmanned aerial vehicles (UAVs) combined with photogrammetric analysis are useful tools to produce accurate 3D maps, which, in turn, help describe the structure of the tree populations. The purpose of this study was to evaluate the use of commercial economical UAVs to assess tree characteristics in the savanna. A Dji Spark UAV was used to map 24 1-ha plots in northern Senegal. The images were processed using Pix4D software to produce a high-resolution canopy height model (CHM). A total of 239 trees were selected and their heights and crown areas were manually measured in the field. A strong correlation was found between UAV and field measurements with R2 = 0.84 for height and R2 = 0.93 for crown area. Based on tree canopy colours and tree morphologies measured by UAV, it was possible to predict tree species with an error rate of 20%, using a random forest classification. This study thus confirms the possibility of using low-cost UAVs to assess tree structures in the savanna not only for research on tree communities in savanna, but also by forestry agencies to inform stakeholders.

This study consists of the development of tree growth models to deduce stands productivity and determine the highest productive species in the conditions of the concerned plantation. Seven Eucalyptus, introduced in the arboretum of Souiniet (north-west of Tunisia, wet Mediterranean bioclimate) in a Cork Oak natural forest, were studied. Stem analysis and non-linear growth modeling regression equations were used to predict wood productivities. Gompertz and Chapman–Richards growth function appeared as being great numerical models to estimate the Eucalyptus tree diameter and height evolutions, respectively. Moreover, an adapted Chapman–Richards model allowed predicting the volume of trees in an efficient manner. The values of mean annual volume productivity of the Eucalyptus spp.studied, allow us to classify them in order of increasing annual productivity, as follows: E. sideroxylon, E. cinerea, E. maidenii, E. macrorhyncha, E. tereticornis, E. viminalis and E. bicostata. The first three Eucalyptus spp. appeared as the best-adapted and most suitable Eucalyptus trees for new plantations in this area. These species had the highest mean annual increments, ranged from 5 to 10 m3.ha−1.year−1 with 15 to 20 years of rotation. E. bicostata is the most promising, with annual average production exceeding 10 m3.ha−1.year−1 after 25 years, and reaching 20 m3.ha−1.year−1 at 40 years old. These modeling approaches provide additional knowledge on the productivity of the different Eucalyptus species, thus enabling forestry operators to simulate the development of forest stands in order to optimize timber production and harvesting.

Miombo woodland is the dominant tropical dry forest formation in Africa. Its importance for local populations’ livelihoods and increased pressure has turned the spotlight on this ecosystem, now considered one of the five global wilderness areas prioritized for conservation and restoration. Forest regeneration is a key to restoring ecosystem services, but the characteristics, conditions and dynamics of this specific biome remain largely understudied. The aim of this study was to analyze the current status and evolution of woody species biodiversity, stand structure and soil properties of regrowth plots after slash-and-burn farming in Mozambique. Our survey focused on the area surrounding Gile National Park in Mozambique, which is dominated by a mosaic of vegetation including mature Miombo woodland, grassland, cropland, and land abandoned after slash-and-burn cycles. We sampled 20 plots in mature woodland and 36 plots in a chronosequence of Miombo regrowth from 1 to 35 years old, grouped in four age classes: 4–6, 8–12; 20–25 and 30–35 years. We observed that woody species richness and diversity increased with time after abandonment until similar values to those in mature woodlands were reached between 20 and 25 years later. Despite the presence of the dominant Miombo tree species belonging to the genera Julbernardia and Brachystegia, after 20–35 years of regeneration species composition remained different from that of mature woodlands. Mean DBH, tree height, and carbon stock increased while tree density decreased along the chronosequence. Tree density and tree carbon stocks in 30–35-year-old Miombo regrowth exceeded those of mature woodland. Soil C stock increased during vegetation regeneration after abandonment. Results suggest that two or three decades are necessary to reach values similar to those of mature woodland. Overall, these findings show that the region has a high regeneration capacity in terms of woody species diversity and soil properties but that disturbances have a long term effect on species composition and stand structure, underlining the importance of integrated landscape management to enhance the provision of ecosystem goods and services.

Made available in DSpace on 2022-04-28T17:20:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 French Space Study Center (CNES, TOSCA 2020 project) National Research Institute for Agriculture, Food, and the Environment (INRAE) Over the past two decades spaceborne LiDARsystems have gainedmomentumin the remote sensing community with their ability to accurately estimate canopy heights and aboveground biomass. This article aims at using the most recent global ecosystem dynamics investigation (GEDI) LiDAR system data to estimate the stand-scale dominant heights (H-dom), and stand volume (V) of Eucalyptus plantations in Brazil. These plantations provide a valuable case study due to the homogenous canopy cover and the availability of precise field measurements. Several linear and nonlinear regression models were used for the estimation of H-dom and V based on several GEDI metrics. H-dom and V estimation results showed that over low-slopped terrain the most accurate estimates of H-dom and V were obtained using the stepwise regression, with an root-mean-square error (RMSE) of 1.33m(R-2 of 0.93) and 24.39 m(3).ha(-1) (R-2 of 0.90) respectively. The principal metric explaining more than 87% and 84% of the variability (R-2) of H-dom and V was the metric representing the height above the ground at which 90% of the waveform energy occurs. Testing the postprocessed GEDI metric values issued from six available different processing algorithms showed that the accuracy on H-dom and V estimates is algorithm dependent, with a 16% observed increase in RMSE on both variables using algorithm a5 vs. a1. Finally, the choice to select the ground return from the last detected mode or the stronger of the last two modes could also affect the H-dom estimation accuracy with 12 cm RMSE decrease using the latter. Univ Montpellier, French Natl Res Inst Agr Food & Environm INRAE, AgroParisTech, CIRAD,CNRS,TETIS, F-34093 Montpellier, France UNESP, Fac Ciencias Agron, BR-18610034 Botucatu, SP, Brazil Suzano SA, BR-13465970 Limeira, Brazil Univ Montpellier, LISAH, Inst Agro, INRAE,IRD, F-34060 Montpellier, France IRD, CNRS, UPS, Ctr Study Biosphere Space,CNES,INRAE, F-31401 Toulouse, France CIRAD, UMR Eco & Sols, F-34398 Montpellier, France IRD, INRA, CIRAD, Eco & Sols, Montpellier, France Univ Montpellier, SupAgro, F-34060 Montpellier, France UNESP, Fac Ciencias Agron, BR-18610034 Botucatu, SP, Brazil

International audience; Key message Decreasing stand density increases resistance, resilience, and recovery ofQuercus petraeatrees to severe drought (2003), particularly on dry sites, and the effect was independent of tree social status. Context Controlling competition is an advocated strategy to modulate the response of trees to predicted changes in climate. Aims We investigated the effects of stand density (low, medium, high; relative density index 0.20, 0.53, 1.04), social status (dominant, codominant, suppressed), and water balance (dry, mesic, wet; summer water balance - 182, - 126, - 96 mm) on the climate-growth relationships (1997-2012) and resistance (Rt), resilience (Rs), and recovery (Rc) following the 2003 drought. Methods Basal area increments were collected by coring (269 trees) in young stands (28 +/- 7.5 years in 2012) of sessile oak (Quercus petraea) in a French permanent network of silvicultural plots. Results We showed that the climate-growth relationships depend on average site-level water balance with trees highly dependent on spring and summer droughts on dry and mesic sites and not at all on wet sites. Neither stand density nor social status modulated mean response to climate. Decreasing stand density increased Rt, Rs, and Rc particularly on dry sites. The effect was independent of tree social position within the stand. Conclusion Reducing stand density mitigates more the effect of extreme drought events on drier sites than on wet sites.

La regeneration naturelle assistee, technique utilisee pour favoriser le developpement du potentiel adventif et du potentiel seminal des arbres, est un mode de reproduction adopte de nos jours pour renouveler et perenniser les formations forestieres. La presente etude a ete realisee dans les plantations de la foret classee de la Lama, situees entre 6°55' et 7°00' de latitude Nord et entre 2°4' et 2°12' de longitude Est. Elle vise a proposer une technique de regeneration naturelle assistee peu couteuse adaptee aux peuplements de teck installes sur des vertisols hydromorphes. Trois methodes de regenerations naturelles assistees ont ete testees sur quatre types de sols (vertisol argilosableux, vertisol argileux, vertisol argilo-calcaire et vertisols argilo-calcaire superficiel). Pour chaque traitement sur chaque type de sol, deux placeaux carrees de 100 m2 ont ete materialises avec chacun huit placettes de 4 m2. La regeneration a ete inventoriee dans chaque placette et des releves ont ete effectues par rapport au nombre, hauteur et circonference au collet des jeunes plants. L’evaluation des couts de la methode a ete realisee grâce a une comptabilite analytique reguliere prenant en compte toutes les depenses d’installation et de maintenance des parcelles experimentales. La densite, hauteur et circonference au collet varient significativement en fonction des types de sol. Toutefois, les plants sont plus developpes en hauteur et en circonference au collet dans les interlignes que sur les lignes. La regeneration sur sol non travaille est le moins couteuse et donc celui a recommander aux gestionnaires des teckeraies de la Lama. Assisted natural regeneration is a technique used to promote the development of the seminal potential of trees. Actually, it is a mode of reproduction adopted to renew and sustain the forests. This study was carried out in the plantations of the Lama reserve (between 6° 55' and 7° 00' north and between 2° 4'and 2° 12' east). It aims to propose an inexpensive assisted natural regeneration method adapted to teak stands installed on hydromorphic vertisols. Three assisted natural regeneration methods were tested on four soil types ((clay-sandy vertisol, clay vertisol, clay-limestone vertisol, and superficial clay-limestone vertisols). For each treatment about each type of soil, two square plots (100 m2) were materialized with eight plots of 4 m2 each one. Regeneration was inventoried in each plot and data are collected about number, height, and circumference at the neck of seeding. The production costs were assessed through regular cost accounting taking into account all the installation and maintenance expenses of the experimental plots. From the results, density, height, and collar circumference vary significantly with soil types. However, the seedlings are more developed in height and circumference at the collar in the interlinings than on the lines. Regeneration on unworked soil is the least expensive and therefore the one to recommend to managers of teak plantations of the Lama.

Made available in DSpace on 2018-12-11T17:17:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-12-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Ministério da Ciência, Tecnologia e Inovação Ministério da Educação Species distribution models (SDMs) are widely used in ecology and conservation. Presence-only SDMs such as MaxEnt frequently use natural history collections (NHCs) as occurrence data, given their huge numbers and accessibility. NHCs are often spatially biased which may generate inaccuracies in SDMs. Here, we test how the distribution of NHCs and MaxEnt predictions relates to a spatial abundance model, based on a large plot dataset for Amazonian tree species, using inverse distance weighting (IDW). We also propose a new pipeline to deal with inconsistencies in NHCs and to limit the area of occupancy of the species. We found a significant but weak positive relationship between the distribution of NHCs and IDW for 66% of the species. The relationship between SDMs and IDW was also significant but weakly positive for 95% of the species, and sensitivity for both analyses was high. Furthermore, the pipeline removed half of the NHCs records. Presence-only SDM applications should consider this limitation, especially for large biodiversity assessments projects, when they are automatically generated without subsequent checking. Our pipeline provides a conservative estimate of a species' area of occupancy, within an area slightly larger than its extent of occurrence, compatible to e.g. IUCN red list assessments. Coordenação de Botânica Museu Paraense Emílio Goeldi, Av. Magalhães Barata 376, C.P. 399 Programa de Pós-Graduação em Ciência Ambientais Universidade Federal Do Pará, Rua Augusto Corrêa 01 Biodiversity Dynamics Naturalis Biodiversity Center, PO Box 9517 Marine and Coastal Management, Deltares, Boussinesqweg 1 Coordenação de Biodiversidade Instituto Nacional de Pesquisas da Amazônia - INPA, Av. André Araújo 2936 EMBRAPA Centro de Pesquisa Agroflorestal de Roraima, BR 174 km 8, Distrito Industrial Herbario Amazónico Colombiano Instituto SINCHI, Calle 20 No 5-44 Department of Integrative Biology University of California Universidad San Francisco de Quito Colegio de Ciencias Biológicas Diego de Robles y Vía Interoceánica Coordenação de Pesquisas em Ecologia Instituto Nacional de Pesquisas da Amazônia - INPA, Av. André Araújo 2936 School of Geography University of Leeds, Woodhouse Lane Department of Wetland Ecology Institute of Geography and Geoecology Karlsruhe Institute of Technology - KIT, Josefstr 1 Biogeochemistry Max Planck Institute for Chemistry, Hahn-Meitner Weg 1 Departamento de Botânica Instituto de Pesquisas Científicas e Tecnológicas Do Amapá - IEPA Campus Do IEPA da Fazendinha, Rodovia JK Km 10 AMAP IRD Cirad CNRS INRA Université de Montpellier, TA A-51/PS2, Bd. de la Lironde Science and Education Field Museum, 1400 S. Lake Shore Drive Coordenação de Dinâmica Ambiental Instituto Nacional de Pesquisas da Amazônia - INPA, Av. André Araújo 2936 Jardín Botánico de Missouri Departamento de Ecologia Universidade Estadual Paulista - UNESP Instituto de Biociências - IB, Av. 24 A 1515 Centro de Biociências Departamento de Ecologia Universidade Federal Do Rio Grande Do Norte, Av. Senador Salgado Filho 3000 Divisao de Sensoriamento Remoto - DSR Instituto Nacional de Pesquisas Espaciais - INPE, Av. dos Astronautas 1758 Herbario Vargas Universidad Nacional de San Antonio Abad Del Cusco, Avenida de la Cultura, Nro 733 Departamento de Geografia Universidade Estadual Paulista - UNESP Instituto de Geociências e Ciências Extas - IGCe Departamento de Biologia Universidade Federal de Rondônia, Rodovia BR 364 s/n Km 9.5 Center for Tropical Conservation Duke University Nicholas School of the Environment Programa de Pós-Graduação em Biodiversidade e Biotecnologia - PPG-Bionorte Universidade Federal de Rondônia Campus Porto Velho, Km 9.5 Instituto Boliviano de Investigacion Forestal Santa Cruz, Av. 6 agosto 28 Km 14,Doble via La Guardia Casilla, 6204 Programa de Pós-Graduação em Ecologia e Conservação Universidade Do Estado de Mato Grosso Instituto de Investigaciones de la Amazonía Peruana - IIAP, Av. A. Quiñones km 2.5 Geography College of Life and Environmental Sciences University of Exeter Departamento de Ciencias Forestales Universidad Nacional de Colombia, Calle 64 x Cra 65 Agteca-Amazonica Facultad de Ciencias Agrícolas Universidad Autónoma Gabriel René Moreno Santa Cruz Prédio da Botânica e Ecologia Embrapa Recursos Genéticos Biotecnologia Parque Estação Biológica, Av. W5 Norte Projeto Dinâmica Biológica de Fragmentos Florestais Instituto Nacional de Pesquisas da Amazônia - INPA, Av. André Araújo 2936 Centre for Tropical Environmental and Sustainability Science College of Science and Engineering James Cook University Laboratório de Ecologia de Doenças Transmissíveis da Amazônia (EDTA) Instituto Leônidas e Maria Deane Fiocruz, Rua Terezina 476 Programa de Pós-graduação em Biodiversidade Saúde Instituto Oswaldo Cruz IOC/FIOCRUZ Pav. Arthur Neiva, Térreo Av. Brasil 4365 Centro de Investigaciones Ecológicas de Guayana Universidad Nacional Experimental de Guayana Calle Chile, urbaniz Chilemex Laboratorio de Ecología de Bosques Tropicales y Primatología Universidad de Los Andes, Carrera 1 # 18a- 10 Programa de Pós-Graduação em Biologia (Botânica) Instituto Nacional de Pesquisas da Amazônia - INPA, Av. André Araújo 2936 Institute of Biodiversity and Ecosystem Dynamics University of Amsterdam, Sciencepark 904 Programa de Ciencias Del Agro y El Mar Herbario Universitario (PORT) UNELLEZ-Guanare Endangered Species Coalition, 8530 Geren Rd MAUA Working Group Instituto Nacional de Pesquisas da Amazônia - INPA, Av. André Araújo 2936 Inventory and Monitoring Program National Park Service, 120 Chatham Lane Center for Conservation Education Sustainability Smithsonian Conservation Biology Institute, 1100 Jefferson Dr. SW, Suite 3123 Biologia Vegetal Universidade Estadual de Campinas, Caixa Postal 6109 Institute of Molecular Plant Sciences University of Edinburgh, Mayfield Rd Royal Botanic Garden Edinburgh, 20a Inverleith Row Programa de Pós-Graduação em Ecologia Instituto Nacional de Pesquisas da Amazônia - INPA, Av. André Araújo 2936 Forest Ecology and Forest Management Group Wageningen University Wageningen University and Research, Droevendaalsesteeg 3, P.O. Box 47 Natural Capital and Plant Health Royal Botanic Gardens Kew Ecosistemas Biodiversidad y Conservación de Especies Universidad Estatal Amazónica, Km. 2 1/2 vía a Tena (Paso Lateral) Museo de Historia Natural Noel Kempff Mercado Universidad Autónoma Gabriel Rene Moreno Santa Cruz, Avenida Irala 565 Casilla Postal 2489 Centro de Biociências Departamento de Botânica e Zoologia Universidade Federal Do Rio Grande Do Norte Campus Universitário Department of Biology University of Miami Coral Fairchild Tropical Botanic Garden Coral Instituto de Biociências Dept. Ecologia Universidade de Sao Paulo - USP, Rua do Matão, Trav. 14, no. 321 Diretoria de Pesquisas Científicas Instituto de Pesquisas Jardim Botânico Do Rio de Janeiro Escuela de Biología Herbario Alfredo Paredes Universidad Central, Ap. Postal 17.01.2177 International Center for Tropical Botany (ICTB) Department of Biological Sciences Florida International University, 11200 SW 8th Street, OE 243 Grupo de Ecología de Ecosistemas Terrestres Tropicales Universidad Nacional de Colombia Sede Amazonía Institute of Biological and Health Sciences Federal University of Alagoas, Av. Lourival Melo Mota, s/n Museu Universitário Centro de Ciências Biológicas e da Natureza Laboratório de Botânica e Ecologia Vegetal Universidade Federal Do Acre Universidad Regional Amazónica IKIAM, Km 7 via Muyuna Cirad UMR Ecofog AgrosParisTech CNRS INRA Univ Guyane Campus Agronomique Iwokrama International Programme for Rainforest Conservation Department of Biological Sciences Humboldt State University, 1 Harpst Street New York Botanical Garden, 2900 Southern Blvd Servicios de Biodiversidad EIRL, Jr. Independencia 405 Herbario Nacional de Bolivia Universitario UMSA, Casilla 10077 Correo Central Missouri Botanical Garden, P.O. Box 299 School of Environmental Sciences University of East Anglia Laboratoire Evolution et Diversité Biologique CNRS Université Paul Sabatier UMR 5174 EDB Department of Forestry Management Universidad Nacional Agraria la Molina, Avenido La Molina, Apdo. 456 School of Geosciences University of Edinburgh, 201 Crew Building, King's Buildings Biology Department Center for Energy Environment and Sustainability Wake Forest University, 1834 Wake Forest Rd Department of Anthropology University of Texas at Austin, SAC 5.150, 2201 Speedway Stop C3200 Andes to Amazon Biodiversity Program Madre de Dios Fundación Puerto Rastrojo, Cra 10 No. 24-76 Oficina 1201 Colegio de Ciencias Biológicas y Ambientales-COCIBA Galapagos Institute for the Arts and Sciences-GAIAS Universidad San Francisco de Quito-USFQ Department of Wildlife Ecology Conservation University of Florida, 110 Newins-Ziegler Hall Fundación Estación de Biología, Cra 10 No. 24-76 Oficina 1201 Embrapa Amazônia Oriental Trav. Dr. Enéas Pinheiro S/no Instituto de Ciencias Naturales Universidad Nacional de Colombia, Apartado, 7945 Amazon Conservation Team, Doekhieweg Oost #24 Facultad de Ciencias Forestales y Medio Ambiente Universidad Nacional de San Antonio Abad Del Cusco, Jirón San Martín 451 Laboratory of Human Ecology Instituto Venezolano de Investigaciones Científicas - IVIC, Ado 20632 Departement EV Muséum National d'Histoire Naturelle de Paris, 16 rue Buffon Instituto de Ciência Agrárias Universidade Federal Rural da Amazônia, Av. Presidente Tancredo Neves 2501 PROTERRA Instituto de Investigaciones de la Amazonía Peruana (IIAP), Av. A. Quiñones km 2 5 ACEER Foundation, Jirón Cusco No 370 Universidad Autónoma Del Beni José Ballivián Campus Universitario Final, Av. Ejercito Regional Norte Amazónico Centro de Investigación y Promoción Del Campesinado, C/Nicanor Gonzalo Salvatierra No 362 Environmental Change Institute Oxford University Centre for the Environment Dyson Perrins Building, South Parks Road School of Agriculture and Food Sciences ARC Centre of Excellence for Environmental Decisions CEED University of Queensland Instituto de Investigaciones para El Desarrollo Forestal (INDEFOR) Universidad de Los Andes, Conjunto Forestal, C.P. 5101 School of Environmental and Forest Sciences University of Washington University of Nottingham, University Park Geography and the Environment University of Texas at Austin, 305 E. 23rd Street, CLA building Laboratório de Ciências Ambientais Universidade Estadual Do Norte Fluminense, Av. Alberto Lamego 2000 Department of Biology University of Maryland GeoIS, El Día 369 y El Telégrafo, 3o Piso Environmental Science and Policy Northern Arizona University FOMABO Manejo Forestal en Las Tierras Tropicales de Bolivia Escuela de Ciencias Forestales (ESFOR) Universidad Mayor de San Simon (UMSS) Agricultural Services Ministry of Agro-Industry and Food Security Agricultural Services Ministry of Agro-Industry and Food Security Mauritius Herbarium Department of Bioscience Aarhus University, Building 1540 Ny Munkegade Ciencias Biológicas Universidad de Los Andes, Carrera 1 # 18a- 10 Medio Ambiente PLUSPRETOL Center for Conservation Education and Sustainability Smithsonian's National Zoo Conservation Biology Institute, National Zoological Park, 3001 Connecticut Ave Tropenbos International, Lawickse Allee 11 PO Box 232 Instituto de Biodiversidade e Floresta Universidade Federal Do Oeste Do Pará Campus Tapajós, Rua Vera Paz Department of Biology University of Missouri Facultad de Biologia Universidad Nacional de la Amazonia Peruana, Pevas 5ta cdra School of Anthropology and Conservation University of Kent, Marlowe Building Herbario Nacional Del Ecuador Universidad Técnica Del Norte Ecology and Biodiversity Group Utrecht University, Padualaan 8 Systems Ecology Free University, De Boelelaan 1087 Departamento de Ecologia Universidade Estadual Paulista - UNESP Instituto de Biociências - IB, Av. 24 A 1515 Departamento de Geografia Universidade Estadual Paulista - UNESP Instituto de Geociências e Ciências Extas - IGCe CAPES: 407232/2013-3-PVE CNPq: 407232/2013-3-PVE Ministério da Ciência, Tecnologia e Inovação: 407232/2013-3-PVE Ministério da Educação: 407232/2013-3-PVE

Tree vigor is often used as a covariate when tree mortality is predicted from tree growth in tropical forest dynamic models, but it is rarely explicitly accounted for in a coherent modeling framework. We quantify tree vigor at the individual tree level, based on the difference between expected and observed growth. The available methods to join nonlinear tree growth and mortality processes are not commonly used by forest ecologists so that we develop an inference methodology based on an MCMC approach, allowing us to sample the parameters of the growth and mortality model according to their posterior distribution using the joint model likelihood. We apply our framework to a set of data on the 20-year dynamics of a forest in Paracou, French Guiana, taking advantage of functional trait-based growth and mortality models already developed independently. Our results showed that growth and mortality are intimately linked and that the vigor estimator is an essential predictor of mortality, highlighting that trees growing more than expected have a far lower probability of dying. Our joint model methodology is sufficiently generic to be used to join two longitudinal and punctual linked processes and thus may be applied to a wide range of growth and mortality models. In the context of global changes, such joint models are urgently needed in tropical forests to analyze, and then predict, the effects of the ongoing changes on the tree dynamics in hyperdiverse tropical forests.

Les études des bois gorgés d’eau découverts sur vingt sites archéologiques localisés à Clermont-Ferrand (Puy-de-Dôme) ont pour objectif de mettre en évidence des pratiques sylvicoles liées aux besoins en bois d’œuvre au cours du développement urbain de la ville d’Augustonemetum durant l’Antiquité. Le croisement des trois disciplines, xylologie, dendrologie et dendrochronologie, est réalisé pour identifier les essences des bois issus des fouilles archéologiques, dater ces derniers quand le nombre de cernes le permet et évaluer la morphologie et l’âge de l’arbre lors de son abattage. Sur cette base, il est possible de percevoir une évolution dans l’approvisionnement en bois et son utilisation, ainsi que dans la composition et la structure des peuplements forestiers exploités. Cette évolution permet de dégager certains traits des pratiques sylvicoles pour ce contexte antique. Studies of waterlogged wood, carried out on twenty ancient archaeological sites located in Clermont-Ferrand (Puy-de-Dôme), have allowed assumption on wood supply: species selection according to timber use (construction, manufacture of objects) and the selection of trees according to age or diameter. These analyses aim to highlight the silvicultural practices in Antiquity in relation with the city Augustonemetum and its timber needs. The crossing of three disciplines (xylology, dendrology and dendrochronology) is performed to identify the wood species from archaeological excavations, dating them when the ring series is enough and to evaluate the morphology and age of the tree when it was felled down. These approaches aim to assess the changes in wood supply and outline their use in order to highlight forestry practices in this antique context.

International audience; Coppice forestry is a conventional silvicultural practice that takes advantage of a tree's capacity to respond to disturbances by sprouting. Sprouting capacity is determined by many intrinsic and extrinsic factors such as parent tree age/size, understory light availability and deer browsing, which, under closed canopy conditions are important limiting factors for stump survival or sprout growth. However, the combined effect of potentially confounding abiotic and biotic factors on stump survival and sprout growth remains elusive, even more so under closed canopy conditions. This study aims to quantify the effect of deer browsing on stump mortality and sprout growth under closed-canopy conditions and to compare this effect with other known determinants. Here we show that stump survival and sprout growth in sessile oak (Quercus petraea Matt.) depend on deer browsing, understory light availability and the diameter of the parent tree. By studying paired fenced-unfenced plots, we confirmed that deer browsing decreased stump survival and inhibited sprout growth. Furthermore, by taking advantage of a gradient in understory light availability in monospecific and mixed stands of sessile oak and Scots pine (Pinus sylvestris L.), we showed a clear positive linear relationship between sprout growth and light availability. This relationship explained the observed differences among stand composition types. Finally, we found that increased understory light availability did not compensate for losses due to deer browsing. In the absence of deer browsing, our results demonstrate that sessile oak stumps regenerate well under closed-canopy conditions and maintain a moderate sprouting capacity at least until the age of 70-80 years old. Partial thinning could therefore be a potential tool to renew light-demanding tree species such as sessile oak in mixed high-forest stands. Nevertheless, we do not recommend coppicing sessile oak under closed canopies unless the oak stumps are protected from deer browsing and understory light availability is optimized as much as possible despite closed-canopy-management objectives.

Concilier le développement des agricultures familiales et la conservation des forêts tropicales dans un contexte de grande pauvreté reste une question d'actualité. Cet ouvrage propose une nouvelle voie en intégrant les agriculteurs comme acteurs de la protection des forêts. Il s'agit de rechercher des bases pour l'action, non pas dans la seule configuration des ressources à protéger, mais dans les logiques d'occupation de l'espace par les agriculteurs et dans les processus de développement compatibles avec la conservation. Ainsi, nous abordons la question de l'ancrage territorial des capacités d'adaptation des agriculteurs à des contraintes environnementales. Elle est appliquée à la région du corridor forestier de Ranomafana-Andringitra dans l'est de Madagascar. L'objectif est de montrer comment les agriculteurs se sont adaptés aux contraintes issues de la mise en place de dispositifs de gestion communautaire des forêts au sein de leurs territoires ancestraux. Ce point de vue est novateur par rapport aux représentations existantes des espaces forestiers qui attribuent souvent aux agriculteurs un rôle purement spéculatif et destructeur. Les agriculteurs sont rarement considérés comme les propres acteurs de leur développement. Cet ouvrage montre comment l'évaluation des capacités d'adaptation des agriculteurs aux contraintes de la conservation permet d'identifier les différents acteurs, activités et territoires à prendre en compte pour concevoir un aménagement intégré et durable des espaces agri-forestiers, visant à mieux concilier conservation et développement.

The greater part of the semi-deciduous moist forests of the Congo basin has been given to logging companies for exploitation. In the next decades, very few of these forests will remain intact. In this paper, we aimed to identify large-scale variations in the structure, composition and functioning of African moist forests that could serve as a baseline for both management and conservation purposes. Commercial forest inventory data were assembled for 49,711 0.5-ha plots, covering an area of more than six million hectares, crossing the borders of Cameroon, Central African Republic and Republic of Congo. Floristic composition was analyzed for a subset of 176 genera reliably identified in the field. Three key functional traits of tropical trees: regeneration guild, leaf phenology, and wood specific gravity, were collected at the species level from various sources, and assigned at the genus level. We first investigated the main variations in forest structure and composition, and identified seven forest types based on these variations. Differences in the percentage of pioneer and deciduous stems, and mean wood specific gravity were tested between forest types. Most of the study area was composed of a mosaic of the structural variations of the forests characterized by the occurrence of Celtis (Ulmaceae) species, which are mostly composed of frequent and abundant genera that formed the common floristic pool of the region. Secondary Musanga (Moraceae) forest is located in repeatedly disturbed areas, along roads and around main cities; mixed Manilkara (Sapotaceae) forest covers a huge area in the southern Central African Republic and in the northern Republic of Congo; and monodominant Gilbertiodendron (Fabaceae) forest is sparsely distributed along rivers. The contrasted structure, composition, and functioning of the forest types imply pronounced differences in population and ecosystem processes, and call for adapted management and conservation strategies.

International audience; 1 Why focus on vulnerability?Forest research has been particularly efficient in detecting the impacts of variability and long-term trends of climate. It is indeed in these ecosystems gathering perennial plants with a long lifespan that the first visible impacts of climate change have been convincingly documented. At first, positive changes in productivity were detected (Becker 1989; Becker et al. 1994; Badeau et al. 1995; Badeau et al. 1996). Improved growth conditions linked to warming, to nitrogen deposition and to increased atmospheric CO2 were perceived fairly early and were also heterogeneous among biogeographical areas due to local limiting factors (trophic or climatic). The first thoughts about the Dryade project were initiated during 2006. In France, the first simulations of potential impacts of available climate scenarios generated awareness, criticism and concerns among managers and foresters (Carbofor, Loustau et al. 2005; Badeau et al. 2010). In addition to climate trends, extreme events had already been identified as a major cause of forest dieback. All major drought events were historically followed by cycles of dieback (Innes et al. 1989; Jones et al. 1993; Landmann 1994; Beniston and Innes 1998; Thomas et al. 2002; Liang et al. 2003; Jurskis 2005). In France, forest dysfunctions induced by the drought events of 2003–2006 were mostly reversible (growth decrease, temporary degradation of crown conditions) but sometimes also irreversible (tree mortality). Several indicators of forest health surveys pointed to a degradation of forest health in France and Europe: abnormal increases in tree mortality (Pauly and Belrose 2005), decline of crown conditions (Lloret et al. 2004; Pauly and Belrose 2005; Belrose et al. 2004, 2006; Carnicer et al. 2011) and upsurge in biotic hazards (Nageleisen 2004; Piou et al. 2006; Rouault et al. 2006).

La prédiction de la biomasse d'un peuplement forestier a` partir de données d'inventaire forestier et d'équations allométriques implique une chaîne de propagation des erreurs qui va de l'erreur d'échantillonnage jusqu'aux erreurs de mesure sur les arbres. En utilisant un jeu de données de 101 arbres d'une forêt tropicale humide du Gabon, nous avons comparé deux sources d'erreurs: l'erreur due au choix de l'équation allométrique, qui a été évaluée avec la moyenne bayésienne de modèles, et l'erreur de mesure de biomasse résultant de l'estimation de la biomasse a` partir du volume au lieu d'une pesée directe. Les différences entre équations allométrique ont induit une erreur inter-modèles d'environ 0,245 sur les données log-transformées, a` comparer a` une erreur résiduelle intra-modèle de 0,297. Comme l'erreur résiduelle se compense lorsque l'on accumule des arbres de manière aléatoire alors que l'erreur inter-modèle est incompressible, cette dernière s'est révélée être une source majeure d'erreur a` l'échelle d'une placette d'1 ha. La mesure de volumes plutôt que de masses a induit une erreur de 0,241 sur les données log-transformées ainsi qu'une surestimation de la biomasse de 19 % en moyenne. Ces résultats ont confirmé le choix de l'équation allométrique comme une source majeure d'erreur mais ont aussi montré que la mesure de volumes pouvait sérieusement biaiser l'estimation de la biomasse.

The cocoa tree (Theobroma cacao L.) is cultivated typically in agroforestry systems in close association with a rich list of tree species and other useful plants on the same plot. Cocoa based agroforestry systems are credited for stocking significant amounts of carbon and hence have the potential to mitigate climate change. Since cocoa yields decrease non-linearly with increasing shade, a need is to design optimal cocoa agroforestry systems with high yields and high carbon stocks. We estimated the carbon stocked in a network of 229 permanent sample plots in cacao-based agroforestry systems and natural forests in five Central American countries. Carbon stocks were fractioned by both system compartments (aboveground, roots, soil, litter, dead wood – fine and coarse, and total) and tree use/form (cocoa, timber, fruit, bananas, shade and ornamentals, and palms). Cocoa plantations were assigned to a five-class typology and tested for independence with growing region using contingency analysis. Most Central American cocoa plantations had mixed or productive shade canopies. Only 4% of cocoa plantations were full sun or rustic (cocoa under thinned natural forest). Cocoa tree density was low (548 ± 192 trees ha−1). Total carbon (soil + biomass + dead biomass) was 117 ± 47 Mg ha−1, with 51 Mg ha−1 in the soil and 49 Mg ha−1 (42% of total carbon) in aboveground biomass (cocoa and canopy trees). Cocoa trees accumulated 9 Mg C ha−1 (18% of carbon in aboveground biomass). Timber and fruit trees stored 65% of aboveground carbon. The annual rate of accumulation of carbon in aboveground biomass ranged between 1.3 and 2.6 Mg C ha−1 y−1. Trade-offs between carbon levels and yields were explored qualitatively using functional relationships documented in the scientific and technical literature, and expert knowledge. We argue that it is possible to design cocoa-based AFS with good yields (cocoa and shade canopy) and high carbon stock levels. The botanical composition of the shade canopy provides a large set of morphological and functional traits that can be used to optimize shade canopy design. Our results offer Central American cocoa producers a rigorous estimate of carbon stocks in their cocoa plantations. This knowledge may help them to certify and sell their cocoa, timber, fruits and other goods to niche markets with good prices. Our results will also assist governments and the private sector in (i) designing better legal, institutional and policy frameworks, local and national, promoting an agriculture with trees and (ii) contributing to the development of the national monitoring, reporting and verification systems required by the international community to access funding and payment for ecosystem services.

1. Estimating forest above-ground biomass (AGB), or carbon (AGC), in tropical forests has become a major concern for scientists and stakeholders. However, AGB assessment procedures are not fully standardized and even more importantly the uncertainty associated with AGB estimates is seldom assessed. 2. Here, we present an R package designed to compute both AGB/AGC estimate and its associated uncertainty from forest plot datasets, using a Bayesian inference procedure. The package builds upon previous work on pantropical and regional biomass allometric equations and published datasets by default but it can also integrate unpublished or complementary datasets in many steps. 3. BIOMASS performs a number of standard tasks on input forest tree inventories: i) tree species identification, if available, is automatically corrected; ii) wood density is estimated from tree species identity; iii) if height data are available, a local height-diameter allometry may be built; else height is inferred from pantropical or regional models; iv) finally, AGB/AGC are estimated by propagating the errors associated with all the calculation steps up to the final estimate. R code is given in the paper and in the appendix for illustration purpose. 4. The BIOMASS package should contribute to improved standards for AGB calculation for tropical forest stands, and will encourage users to report the uncertainties associated with stand-level AGB/AGC estimates in future studies.

In forest ecosystems, the specific influence of soil resources on stand productivity is difficult to assess because many other ecological variables also affect tree growth. In this study, we took advantage of a natural soil gradient, from shallow calcic soil to deep acidic soil, all with similar climate, atmospheric depositions, species composition and management, to determine the relationship between soil nutritive resources and the growth and mineral nutrition of a beech ( Fagus sylvatica ) mature forest of Northeastern France. Soil resources were assessed through the quantification of the stocks of available water and mineral nutrients (Ca, Mg, K and P 2 O 5 ). Beech stand growth and mineral nutrition were determined through the use of several indicators, i.e., standing aboveground biomass and annual biomass production, potential growth index (prediction of the height of dominant trees at 100 years) and foliar nutrient content. We observed a gradient of nutritive resources in soils as well as a gradient of stand growth on the study site: the current aboveground biomass was highest on the calci-brunisol which presented the highest water and nutrient stocks while it was lowest on the rendisol, characterized by a very low water holding capacity and a very low stock of available K. However, the growth of beech trees on the rendisol was equivalent to the highest growth classes of beech trees in France, and K nutrition was optimal. Observations on the study site suggest that, in favorable climate conditions, some biological adaptation processes, such as an efficient root colonization as well as an efficient nutrient cycling may allow to maintain stand growth and nutrition on soils with low water and nutrient reserves. The fertility of forest soils has thus to be assessed in a dynamic way by integrating nutrient fluxes as well as the adaptations of trees to environmental constraints. The biological processes become an increasingly important part in the conservation of soil fertility, notably in the perspective of global changes.

Entretenir sa forêt: Fiche technique; Peu de temps après la création de l’IBP en 2008, le CRPF Midi-Pyrénées a proposé cette méthode à un propriétaire tarnais qui réalisait son PSG et souhaitait mieux intégrer la biodiversité ordinaire dans sa gestion courante. C’est ce travail qui est ici relaté. Notons qu’en complément à l’IBP, le propriétaire a utilisé ultérieurement la démarche BIOFIL 1, développée par le CRPF Midi-Pyrénées et permettant notamment de mieux repérer à l’échelle de la forêt leséléments de biodiversité remarquables.

La naturalité biologique n'est pas intrinsèquement liée à l'arrêt de l'exploitation mais correspond à la présence d'éléments structuraux typiques de forêts en évolution naturelle tels que les bois morts ou les dendromicrohabitats. Par ailleurs d'autres attributs ou propriétés du peuplement peuvent influencer la biodiversité. Les effets de l'ensemble de ces caractéristiques sur les 7 taxons du projet GNB sont examinés ici, avec une discussion sur la manière d'interpréter ces résultats pour la gestion forestière.

Survival analysis methods make better use of temporal information, accommodate multiple levels of explanatory variables, and are meant to deal with interval-censored data. In a context of harvest modeling, this approach could improve some known limitations. In this study, we used data from a network of permanent plots in the province of Quebec, Canada, as a real-world case study. We tested the potential of survival analysis to predict plot-level harvest probabilities from plot- and regional-level variables. The approach also included random effects to account for spatial correlations.The results showed the potential of survival analysis to provide annual predictions of harvest occurrence. Both regional and time-varying variables, as well as spatial patterns, had important effects on the probability of a plot to be harvested. Respectively, reductions in the annual allowable cut volumes led to a decrease in the harvest probabilities. Greater harvest probabilities were associated with the broadleaved dynamics class and higher values of basal area. In contrast, they were decreased by stem density and slope classes.The spatial random effect resulted in an improvement of the model fit. Our plot- level model improved some limitations reported in previous studies by taking the effect of a time-varying regional variable into account.; Les méthodes d’analyse de survie utilisent mieux l’information temporelle, tiennent compte de multiples niveaux de variables explicatives et sont destinées à traiter des données censurées par intervalle.Dans un contexte de modélisation de la récolte, cette approche pourrait améliorer certaines limites connues. Dans cette étude, nous avons utilisé des données d’un réseau de placettes permanentes de la province de Québec, au Canada, pour servir d’étude de cas concret. Nous avons testé le potentiel de l’analyse de survie pour prédire les probabilités de récolte à l’échelle de la placette, à partir de variables associées à la placette et à la région. L’approche comprenait également des effets aléatoires pour tenir compte des corrélations spatiales.Les résultats ont montré le potentiel de l’analyse de survie pour fournir des prédictions annuelles de l’occurrence de la récolte. Les variables régionales et les variables qui évoluent en fonction du temps, ainsi que la configuration spatiale, avaient des effets importants sur la probabilité qu’une placette soit récoltée. Les réductions de la possibilité annuelle de coupe entraînaient une diminution des probabilités de récolte. Des probabilités de récolte plus grandes étaient associées à la classe de dynamique forestière feuillue et à des valeurs plus élevées de la surface terrière. Inversement, elles étaient diminuées par la densité des tiges et les classes de pente.L’effet aléatoire spatial a entraîné une amélioration de l’ajustement du modèle. Notre modèle à l’échelle de la placette a amélioré certaines limites signalées dans les études précédentes en prenant en compte l’effet d’une variable régionale qui évolue dans le temps.

Pour saisir la portée et l'intérêt du projet GNB, il ne suffit pas de connaître ses objectifs, dûment fondés sur un bilan circonstancié de l'état des connaissances. Il faut aussi appréhender sa démarche « expérimentale », à commencer par la stratégie d'échantillonnage et d'inventaires ; il faut comprendre le choix de méthodes d'analyse statistique innovantes mais complexes, avec en particulier la notion de magnitude des effets pour que les résultats puissent avoir une « lecture » opérationnelle. Impossible de résumer en quelques mots la réflexion exigeante qui a présidé à la conception du projet.

Key message This data set provides unique empirical data from triplets of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) across Europe. Dendrometric variables are provided for 32 triplets, 96 plots, 7555 trees and 4695 core samples. These data contribute to our understanding of mixed stand dynamics. Dataset access at http://dx.doi.org/10.5061/dryad.8v04m. Associated metadata available at https://metadata-afs.nancy.inra.fr/geonetwork/apps/georchestra/? uuid=b3e098ca-e681-4910-90990e25d3b4cd52&hl=eng.; Key message :This data set provides unique empirical data from triplets of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) across Europe. Dendrometric variables are provided for 32 triplets, 96 plots, 7555 trees and 4695 core samples.These data contribute to our understanding of mixed stand dynamics.Dataset access at http://dx.doi.org/10.5061/dryad.8v04m.Associated metadata available at https://metadata-afs.nancy.inra.fr/geonetwork/apps/georchestra/? uuid=b3e098ca-e681-4910-90990e25d3b4cd52&hl=eng.

Cet article conclut le dossier consacré au projet Gestion forestière, Naturalité, Biodiversité, qui s'est attaché à comparer la biodiversité de sept groupes taxonomiques (flore vasculaire, bryophytes, champignons lignicoles, carabes, coléoptères saproxyliques, oiseaux et chiroptères) dans des réserves forestières intégrales et dans leurs équivalents en forêt exploitée. Que retenir des résultats ? Tout d'abord, que des mesures directes de biodiversité confortent les dispositions en vigueur pour la conservation de la biodiversité forestière. Ensuite, que les premiers constats appellent de nouvelles analyses et invitent à approfondir la présentation des résultats, en travaillant avec les forestiers pour des analyses de magnitude plus réalistes.

• 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.

La naturalité dite anthropique correspond au fait de soustraire les peuplements aux perturbations liées à l'exploitation des bois. Elle a une composante temporelle liée à la durée depuis l'arrêt d'exploitation, et une composante spatiale qui correspond à la taille de la réserve mais aussi à d'autres aspects comme la proportion en réserve dans le paysage. Comment la biodiversité, vue comme la richesse spécifique des 7 taxons étudiés dans GNB, réagit-elle aux variables de naturalité anthropique ? Réponse mitigée.

Comment analyser la réponse de la biodiversité à la mise en réserve intégrale ? La première étape est d'explorer les données de structure forestière et de description spatiotemporelle pour identifier les caractéristiques déterminantes, les « variables explicatives » de modèles destinés à expliquer les variations de biodiversité entre forêts exploitées et réserves. Originalité du projet GNB : la démarche se réfère à la notion de naturalité(s), en distinguant variables de naturalité anthropique et variables de naturalité biologique.

Le réseau des réserves forestières a plus de 150 ans. Il s'est beaucoup étoffé durant les dernières décennies. Outil de conservation de la Nature, il permet aussi d'inspirer la gestion courante. Pour cela une observation rigoureuse de la biodiversité et des peuplements est nécessaire. C'est ce que propose le projet GNB.

The total uptake of carbon dioxide by ecosystems via photosynthesis (gross primary productivity, GPP) is the largest flux in the global carbon cycle. A key ecosystem functional property determining GPP is the photosynthetic capacity at light saturation (GPPsat), and its interannual variability (IAV) is propagated to the net land–atmosphere exchange of CO2. Given the importance of understanding the IAV in CO2 fluxes for improving the predictability of the global carbon cycle, we have tested a range of alternative hypotheses to identify potential drivers of the magnitude of IAV in GPPsat in forest ecosystems. Our results show that while the IAV in GPPsat within sites is closely related to air temperature and soil water availability fluctuations, the magnitude of IAV in GPPsat is related to stand age and biodiversity (R2 = 0.55, P < 0.0001). We find that the IAV of GPPsat is greatly reduced in older and more diverse forests, and is higher in younger forests with few dominant species. Older and more diverse forests seem to dampen the effect of climate variability on the carbon cycle irrespective of forest type. Preserving old forests and their diversity would therefore be beneficial in reducing the effect of climate variability on Earth's forest ecosystems. Interannual variability (IAV) of the net carbon dioxide exchange over land is globally the main determinant of the variability of atmospheric CO2 growth rate1,2. So understanding the factors controlling the IAV in CO2 fluxes is essential to improve the predictability of the global carbon cycle3. Ecosystem biotic properties — such as soil and canopy nutrient status, rates of change in physiological properties of the vegetation, or the sensitivity of these properties to environmental factors — influence ecosystem CO2 exchange. Recent studies have shown that the IAV of the carbon budget can be better explained by variation in biotic properties of ecosystems such as photosynthetic capacity (GPPsat) than directly by environmental and climatic drivers4,​5,​6. GPPsat is defined as the value of gross primary productivity (GPP) at saturating light under non-stressed conditions, minimizing the influence of anomalous hydrometeorological conditions (for example, droughts and heatwaves), which potentially affect photosynthesis. A robustly retrieved characterization of GPPsat can be regarded as an ecosystem functional property reflecting the physiological response of the ecosystem to the environment. Given that IAV of GPPsat must propagate to observed GPP, this quantity is thought to be a key variable in understanding IAV of carbon fluxes7. In fact, recent studies demonstrated that GPPsat correlates more strongly than any climatic variable with annual GPP8, but also correlates with net ecosystem CO2 exchange5. The magnitude of IAV in GPPsat has been shown to exhibit considerable variation across ecosystems9, yet no obvious explanation for this pattern has been reported in the literature. However, the consequences are important: a low IAV in GPPsat would suggest that ecosystem functioning is not very sensitive to climatic variability, and that it preserves its functionality under the influence of that variability — and, likewise, high IAV is a consequence of high sensitivity. The capability of an ecosystem to preserve its functioning and structure over time (after external disturbances or climate extremes), is often defined as ecosystem stability and is linked to ecosystem resilience10. Using this terminology, low values of IAV in GPPsat can be understood as a characterization of high ecosystem functional stability. The relation of ecosystem functionality, structure and stability has been a matter of debate for many decades in the field of ecology. In particular, the diversity of vascular plants has been investigated as a stabilizing factor with respect to variations in productivity, for example by buffering the ecosystem’s sensitivity to climate extremes11. However, it is also well known that plant diversity is co-limited by soil properties12, ecosystem management, and climate conditions. Another variable to consider is stand age (the mean age of the forest stand or the number of years after a major stand replacement after disturbance), which may affect ecosystem stability through adaptation, particularly of trees to their environment — hence increasing ecosystem resilience to climate variability13. Moreover, structural parameters such as canopy cover, rooting depth, canopy height or leaf area index (LAI), which also depend on tree species diversity and stand age14, have an important effect on the ecosystem response to variation in environmental drivers since they define the capacity of trees to access resources such as water and light15. For instance, a regional study in the Amazon basin has shown that GPP, derived from the remotely sensed enhanced vegetation index, is less sensitive to environmental influences in regions with high canopy cover16. Despite this growing body of ecological knowledge, it remains largely uncertain which factors stabilize ecosystem functional properties at the global scale. In particular, we do not understand the causes of variability of specific ecosystem functional properties, such as photosynthetic capacity across ecosystem types, which ultimately controls ecosystem productivity. Here we hypothesize that stand age and species diversity play an important role in stabilizing ecosystem photosynthetic capacity. We test this hypothesis while also considering other factors related to climate, water availability, forest structure and soil properties that might have direct or indirect effects on ecosystem photosynthetic capacity. In this study, we used measurements of ecosystem-level fluxes, and climate variables (temperature, precipitation, and water availability), species richness, stand age, forest structure (canopy cover, height, and LAI), and soil properties (nutrient availability17) derived from satellite data, in situ observations and the literature (see the Methods). We used half-hourly ecosystem-level GPP fluxes estimated by the means of the eddy-covariance technique at 50 FLUXNET sites18 with at least 4 years of measured fluxes, and with different vegetation types across different climatic regions. We included data from evergreen forest (EF) as well as deciduous broadleaved and mixed forest (DBMF) located in temperate, boreal, mediterranean, tropical and dry climate regions (Supplementary Fig. 1 and Table 1). All 50 sites have information on stand age (referred to simply as ‘age’ in Figs 1–3) and species richness in addition to the CO2 flux data. Species richness (‘sp. no.’ in Figs 1–3) is the number of dominant plant species (for example tree or herb) that account for a cumulative abundance of 90 percent at a given site. We collected additional information on (i) canopy cover, (ii) canopy height, (iii) LAI, (iv) temperature and precipitation, and (v) soil water availability index (WAI) for a subset of 44 sites; and (vi) an index of nutrient availability for 36 sites compiled from the literature17 (see Methods).

This article analyses the density, spatial distribution, and diameter structure of two neotropical tree species, Dipteryx odorata (Aubl.) Willd. and Copaifera reticulata Ducke, in undisturbed forests, logged forests, and forests used for the extraction of Non-Timber Forest Products (NTFPs). Both species are commercially harvested for timber and non-timber products which can fetch high prices on national and international markets. In undisturbed forests, both species display a low tree density, a random adult tree distribution pattern and a flat diameter structure, or one biased towards larger trees. The random spatial distribution pattern did not vary in the three types of forests analysed, whereas individual density and diameter structure did. The NTFP extraction areas exhibited the highest population densities for both species. In the logged forests, there was a lower density of very large D. odorata trees, while the areas used for D. odorata seed extraction showed a drastic reduction in the frequency of young trees. The results of this study seem to suggest that oil extraction from C. reticulata does not have any effect on the regeneration of that species, whereas D. odorata seed collection could affect the viability of populations.

A two-level data set consists of entities of a higher level (say populations), each one being composed of several units of the lower level (say individuals). Observations are made at the individual level, whereas population characteristics are aggregated from individual data. Cluster analysis with subsampling of populations is a cluster analysis based on individual data that aims at clustering populations rather than individuals. In this article, we extend existing optimality criteria for cluster analysis with subsampling of populations to deal with situations where population characteristics are not the mean of individual data. A new criterion that depends on the Mahalanobis distance is also defined. The criteria are compared using simulated examples and an ecological data set of tree species in a tropical rain forest.

International audience; 1 Considering that the spatial pattern of trees is a footprint of the biological processes that drive their dynamics, increasing work has been undertaken to analyse spatial patterns and fit spatial point processes to them. When diameter is taken into account, the underlying point process is a marked point process. The question then is how to correctly model the dependence between the mark and location, and the different patterns at the different scales, to gain understanding of the underlying biological processes. # 2 The data used comes from the Paracou rain forest in French Guiana (5°15′ N, 52°55′ W). The spatial pattern of trees in this forest exhibits regularity at small distances (c. 6 m) and clustering at larger distances (c. 30 m). The pattern is linked to diameter, with a shift from clustering to regularity as trees grow. # 3 Two models of spatial pattern are used. The first one is pattern-driven in the sense that it breaks down the observed pattern into a mixture of regular, clustered and random contributions. The second one is process-based and uses a simple individual-based space-dependent model of forest dynamics as a simulation algorithm. It is obtained as the limit of this spatio-temporal model when time tends to infinity. # 4 Both models are consistent with the observed pattern, with a better fit provided by the second model. Moreover this second model provides a biological interpretation of the observed pattern in terms of forest dynamics. However the first model's implementation is simpler (both for simulation and for parameter estimation). # 5 Synthesis. Modelling the spatial pattern of plants using spatial point processes gives insights into the biological processes that drive their dynamics. It allows the reconstruction of their dynamics given only a snapshot of plant locations. Very few solutions exist to model complex marked spatial patterns when point location and mark are dependent. We defined and compared two point processes that successfully modelled the spatial pattern of trees in a rain forest with interaction between tree location and tree size. Both models highlight competition (either symmetric or asymmetric) as a driving process towards regularity. The second model further reveals a self-organizing dynamic with a feedback effect of competition

Successive ecological filtering processes including dispersal limitation (species ability to reach an environment), environmental filtering (local abiotic constraints to species settlement) and biotic interactions among plants (competition, facilitation) and across trophic levels act upon regional species pools to form dynamic and transient plant assemblages. Native herbivorous ungulates regularly disperse numerous diaspores (zoochory), create local chemical and physical heterogeneity through small scale soil disturbance (ecosystem engineering) and also selectively consume plants (herbivory), whereby they shape plant assemblages by intervening in the different ecological filtering processes. The ecological processes through which large ungulates locally affect both abiotic and biotic conditions make plant communities more susceptible to invasion by non-resident species (both native colonizers and exotic invaders); I therefore discuss ungulates' role in shaping plant assemblages within the framework of the theory of invasibility proposed by Davis et al. (2000). Here, I specifically highlight how complementary zoochorous processes in a guild of large ungulates affect the composition and spatial distribution patterns of plant assemblages. In this manuscript, I present different results addressing the different filtering effects. For instance, results from a trait-based meta-analysis show how endozoochory, hoof- and hair-epizoochory differentially filter the regional species pool. Interactions among vectors, seeds and plant traits also intervene in the seed dispersal cycle (emigration, transfer and settlement) and seed dispersal effectiveness. I also highlight how closely ungulates may combine seed dispersal with abiotic filtering. My colleagues and I show that herbivorous ungulates, as selective and daily long-distance seed dispersal vectors, play a role in determining the spatial and temporal dynamics of meta-communities. These animals are likely to affect plant responses to global changes such as habitat fragmentation, land use changes and climate warming, and may have contributed to plant migration patterns since the last glaciation. As primary consumers they also occupy an in-between position within the food web and may thus compete for feeding resources with other groups such as insects with potential trophic cascading effects on bird communities. Through the many interactions ungulates are involved in, we have to consider their global role as dynamic actors in ecosystem functioning and potential tools to rehabilitate degraded habitats via seed dispersal and associated engineering effects. / Les processus successifs de filtrage écologique dont le frein à la dispersion (la capacité des plantes à atteindre un environnement), le filtre environnemental (contraintes abiotiques locales à l'installation des plantes), et les interactions biotiques entre plantes (compétition, facilitation) et avec d'autres niveaux trophiques agissent sur le pool régional de plantes pour créer localement des assemblages de plantes dynamiques et transitoires. Les ongulés herbivores autochtones dispersent régulièrement de nombreuses diaspores (zoochorie), créent localement de l'hétérogénéité chimique et physique par des perturbations du sol de faible surface (effets d'ingénierie) et consomment sélectivement les plantes (herbivorie), façonnant ainsi les assemblages de plantes en intervenant à chaque niveau de filtrage écologique. Les processus écologiques par lesquels les grands ongulés affectent localement les conditions abiotiques et biotiques rendent les communautés de plantes plus sujettes à l'invasion par des espèces non résidentes (à la fois colonisatrices autochtones et invasives exotiques) ; je discute ainsi du rôle des ongulés sauvages dans la fluctuation des ressources disponibles pour l'assemblage des communautés végétales dans le cadre de la théorie de l'invasibilité proposée par Davis et al. (2000). En particulier, j'illustre comment les mécanismes complémentaires de dispersion zoochore par une guilde de grands ongulés modulent la composition et les patrons de distribution spatiale des assemblages de plantes. Je présente dans ce manuscrit différents résultats traitant des effets des ongulés sauvages comme filtre écologique. Par exemple, une méta-analyse européenne basée sur les traits des plantes montre comment l'endozoochorie, l'épizoochorie sous les sabots et dans le pelage filtrent différentiellement le pool régional de plantes. Les interactions entre traits des vecteurs, des diaspores et des plantes interviennent dans les trois phases de la dispersion (émigration, transfert et immigration) et l'efficacité de la dispersion. Je mets aussi en évidence comment les ongulés combinent étroitement zoochorie et effets d'ingénierie physique et chimique. Ainsi, mes collègues et moi suggérons que les ongulés herbivores, en tant que vecteurs quotidiens, sélectifs et à longue distance des diaspores peuvent jouer un rôle déterminant dans les dynamiques spatiales et temporelles des méta-communautés. Ces animaux sont susceptibles de moduler la réponse des plantes aux changements globaux contemporains : fragmentation des habitats, changement d'utilisation des terres et réchauffement climatique, et ont probablement contribué aux patrons passés de migration post-glaciaire. En tant que consommateurs primaires, ils occupent une position clé au sein de la chaîne alimentaire et peuvent ainsi concurrencer d'autres groupes, comme l'entomofaune, dans l'accès aux ressources avec de potentiels effets de cascades trophiques sur les communautés d'oiseaux. Au travers des multiples interactions dans lesquelles sont impliqués les ongulés sauvages, nous avons à les considérer plus généralement comme des acteurs dynamiques dans les assemblages de plantes, le fonctionnement des écosystèmes et des agents potentiels de restauration d'habitats dégradés via la zoochorie et les effets associés d'ingénierie.

National audience; La gestion forestière peut être considérée comme un investissement auquel le concept de l’optimisation économique est applicable. La longueur des cycles de production forestière et l’arrivée d’événements inattendus conduit cependant le gestionnaire à prendre des décisions différentes de celles qui ont été définies comme optimales au moment de la mise en place du peuplement forestier. Cet article explore les effets de l’incertitude en matière de prix et de risque tempête sur le cas de la hêtraie.

Motivated by the analysis of the impact of ecological processes on spatial distribution of tree species, we introduce in this paper a novel approach to detect spatial cluster of points. Our procedure is based on an iterative transformation of the distance between points into a measure of closeness. Our measure has the advantage of being independent of an arbitrary cluster shape and allowing adjustment for covariates. The comparison of the observed measure of closeness to a reference point process leads to a hierarchical clustering of spatial points. The selection of the optimal number of clusters is performed using the Gap statistic. Our procedure is illustrated on a spatial distribution of the Dicorynia guianensis species in the French Guiana terra firme rainforest.

National audience

Understanding the behaviour of individual-based models of forest dynamics becomes difficult as their complexity increases. A useful strategy consists in simplifying parts of the model, then scrutinizing for possible differences between the original model’s predictions and those of the simplified version. This strategy is adopted to understand the role of space in a complex individual-based space-dependent model of tropical rain-forest dynamics in French Guiana. The model is made of three components: growth, recruitment and mortality. Two aggregation techniques are used to simplify space-dependent interactions into space-independent interactions: the mean-field approximation and an ad hoc approximation that considers pair interactions. Each technique is applied to one of the components of the model, the other two being left untouched, or to all components. Nine versions of the model (including the original one) are thus compared on the basis of the predicted diameter distribution at stationary state. The fully distance-independent models are consistent with the original one, whereas growth and recruitment significantly modify the model’s predictions when simplified by the aggregation techniques. The interplay between the spatial distribution of trees at the population level and the dynamic processes at the individual level is thus understood, and the excessive impact of the mortality component that favours the establishment of clusters of big trees is diagnosed.

The influence of environmental conditions and distance to nearest conspecific adult was determined to explain the distribution of saplings of six tree species in a lowland rain forest of French Guiana. The six focal species were three anemochorous light-demanding non-pioneer species: Dicorynia guianensis , Qualea rosea , Tachigali melinonii , and three zoochorous shade-tolerant species: Bocoa prouacensis , Oxandra asbeckii , Pogonophora schomburgkiana . The study was conducted at the research station of Paracou on forest plots differing in past logging treatments. The description of local environment included a characterization of past disturbance intensity ( N = 5 variables), current stand ( N = 4) and canopy structure ( N = 3). Zero Inflated Poisson models were calibrated for each species to explain sapling numbers according to environmental conditions and distance to the nearest conspecific adult. These models extend generalized multiple regression to the case of discrete data with many zero counts. Model predictions were consistent with species temperaments: as expected, saplings of the light-demanding species were found more in disturbed and open local conditions while more saplings of the shade-tolerant species survived in stable and dense places. Predicted establishment curves of saplings around adults showed contrasting behavior among the species and did not systematically match with a priori expectations. These results are discussed in relation with dispersal syndromes and known establishment patterns in forest regeneration. Both differences in species shade-tolerance in early regeneration stages and dispersal limitation proved to account for sapling distribution in the understorey.

We investigated the relevance of understory vegetation in indicating site productivity as expressed by sessile oak (Quercus petraea Matt. Liebl.) site index over a large territory. The relationships between site index and (1) understory vegetation or (2) soil, topography and climate were studied using data from 99 even-aged high-forest stands located in northern France. Multiple regressions using floristic indices as predictors explained the same part of variance in site index as regressions using climate, topography, and soil factors (R2 = 0.49 to 0.60). However, better models were obtained by combining floristic and abiotic variables (R2 = 0.57 to 0.69). We concluded that (1) site productivity can be assessed with the same precision using understory vegetation or abiotic variables separately, even over a large region, but (2) it would be more appropriate to combine soil physical and chemical properties, climate and topography with floristic indices to estimate sessile oak site index., La végétation du sous-bois peut-elle prédire correctement l'indice de fertilité ? Comparaison de l'efficacité des indices floristiques et abiotiques en futaie régulière adulte de chêne sessile dans la moitié nord de la France. L'objectif était d'étudier sur un vaste territoire la pertinence de la végétation du sous-bois pour prédire le niveau de productivité d'un peuplement, mesurée par l'indice de fertilité du chêne sessile (Quercus petraea Liebl.). Les relations entre cet indice et (1) la végétation du sous-bois ou (2) le climat, la topographie et le sol ont été étudiées sur 99 peuplements adultes de futaie régulière situés dans la moitié nord de la France. Les régressions multiples basées sur ces indices floristiques expliquent la même part de variance de l'indice de fertilité que les régressions basées sur le climat, la topographie et le sol (R2 = 0,49 à 0,60). Cependant, de meilleurs modèles sont obtenus en combinant les variables floristiques et abiotiques (R2 = 0,57 à 0,69). Nous concluons que la productivité d'une essence peut être évaluée avec le même niveau de précision en utilisant séparément la végétation du sous-bois et les descripteurs abiotiques, y compris sur un vaste territoire. Mais nous recommandons pour une meilleure estimation de combiner à la fois les propriétés physiques et chimiques du sol, le climat, la topographie et les indices floristiques.