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Forests have to cope with three interlinked transitions: climatic transition, energetic transition and economic transition with an up-rising demand on wood such as new needs to feed up the emerging bioeconomy. Meanwhile, forests are part of a world-wide, nature-based solution for climate warming mitigation. although forests are at the center of territorial conflicts. Thus. it is urgent to foster the development of innovative forest management practices taking into account the quadruple interaction 'which forest resources x in which biogeoclimatic zones x with which forest managements x for which purposes'. By doing so we expect to provide decision tools for forest managers and policy makers. The French national infrastructure IN-SYLVA federates in a common organization tropical and tempered in situ experimentation networks managed by the public and private sectors (5.000 experimental trials covering 4.000ha) as well as in lab facilities ( functional ecology, wood properties and genomics) and in silico resources (data bases and models). In such a wav IN-SYLVA deals jointly with forest management, biogeochemical features, genetics and economy. IN-SYLVA will guide public policies by scientific or technical enlightening and will be the link to the academic and professional sphere. Within the Open Science framework IN-SYLVA data policy and practices will contribute to the sharing of data and knowledge. Our first practical goal is to set up an information system federating the distributed resources and providing through the IN-SYLVA data portal the necessary metadata for discovery and access to the data collected by the experimental networks.

International audience; 1. Regional above-ground biomass estimates for tropical moist forests remain highly inaccurate mostly because they are based on extrapolations from a few plots scattered across a limited range of soils and other environmental conditions. When such conditions impact biomass, the estimation is biased. The effect of soil types on biomass has especially yielded controversial results. 2. We investigated the relationship between above-ground biomass and soil type in undisturbed moist forests in the Central African Republic. We tested the effects of soil texture, as a surrogate for soil resources availability and physical constraints (soil depth and hydromorphy) on biomass. Forest inventory data were collected for trees >= 20 cm stem diameter in 2754 0.5 ha plots scattered over 4888 km(2). The plots contained 224 taxons, of which 209 were identified to species. Soil types were characterized from a 1:1 000 000 scale soil map. Species-specific values for wood density were extracted from the CIRAD's data base of wood technological properties. 3. We found that basal area and biomass differ in their responses to soil type, ranging from 17.8 m(2) ha(-1) (217.5 t ha(-1)) to 22.3 m(2) ha(-1) (273.3 t ha(-1)). While shallow and hydromorphic soils support forests with both low stem basal area and low biomass, forests on deep resource-poor soils are typically low in basal area but as high in biomass as forests on deep resource-rich soils. We demonstrated that the environmental filtering of slow growing dense-wooded species on resource-poor soils compensates for the low basal area, and we discuss whether this filtering effect is due to low fertility or to low water reserve. 4. Synthesis. We showed that soil physical conditions constrained the amount of biomass stored in tropical moist forests. Contrary to previous reports, our results suggest that biomass is similar on resource-poor and resource-rich soils. This finding highlights both the importance of taking into account soil characteristics and species wood density when trying to predict regional patterns of biomass. Our findings have implications for the evaluation of biomass stocks in tropical forests, in the context of the international negotiations on climate change.

International audience; The sustainability of fast-growing tropical Eucalyptus plantations is of concern in a context of rising fertilizer costs, since large amounts of nutrients are removed with biomass every 6–7 years from highly weathered soils. A better understanding of the dynamics of tree requirements is required to match fertilization regimes to the availability of each nutrient in the soil. The nutrition of Eucalyptus plantations has been intensively investigated and many studies have focused on specific fluxes in the biogeochemical cycles of nutrients. However, studies dealing with complete cycles are scarce for the Tropics. The objective of this paper was to compare these cycles for Eucalyptus plantations in Congo and Brazil, with contrasting climates, soil properties, and management practices. The main features were similar in the two situations. Most nutrient fluxes were driven by crown establishment the two first years after planting and total biomass production thereafter. These forests were characterized by huge nutrient requirements: 155, 10, 52, 55 and 23 kg ha_1 of N, P, K, Ca and Mg the first year after planting at the Brazilian study site, respectively. High growth rates the first months after planting were essential to take advantage of the large amounts of nutrients released into the soil solutions by organic matter mineralization after harvesting. This study highlighted the predominant role of biological and biochemical cycles over the geochemical cycle of nutrients in tropical Eucalyptus plantations and indicated the prime importance of carefully managing organic matter in these soils. Limited nutrient losses through deep drainage after clear-cutting in the sandy soils of the two study sites showed the remarkable efficiency of Eucalyptus trees in keeping limited nutrient pools within the ecosystem, even after major disturbances. Nutrient input–output budgets suggested that Eucalyptus plantations take advantage of soil fertility inherited from previous land uses and that long-term sustainability will require an increase in the inputs of certain nutrients.

The increasing demand for wood products is not satisfied by natural forests, and forest plantations are expected to provide a larger part of the global wood supply in the future. Eucalyptus is the dominant species planted in the tropics. Intensification of wood production will rely mainly on gain of productivity and on extension of afforested area on marginal zones. Wood production does not only depend on gross primary production (GPP) but also on carbon partitioning between growth (NPP) and respiration, and on NPP partitioning among the different plant organs (allocation). Less than one third of GPP is allocated to wood production in planted forest ecosystems and we hypothesized that this fraction varies among genotypes, or because of soil fertility, in relation to productivity. The partitioning of aboveground NPP between leaf, branch and stem growth was compared in four Eucalyptus plantations located in Congo and Brazil over an entire rotation (6 years). In addition, total below ground carbon allocation was estimated from soil respiration and litter fall measurements. Two clones differing in productivity were studies in Congo where productivity is known to be much less important than in Brazil. Two plots (fertilized or not with K) were studied in Brazil. In Congo, the wood production was twice higher in the most productive clone (UG) compared to the less productive one (PF1). This was due to a higher aboveground NPP, the surplus being allocated to wood production. In addition, an increase in leaf lifespan reduced the amount of carbon allocated to leaf production. Similar conclusions can be drawn when comparing K fertilised and control stand in Brazil where most of the surplus of aboveground NPP in fertilised plots was allocated to wood production and where leaf lifespan was also increased. Soil respiration increased in both sites with increasing NPP reflecting that more carbon is allocated below ground in these stands. A better understanding of genetic and environmental control on carbon allocation is required for accurately predicted tree yield, especially in marginal area where plantations are thought to extent.

Les modéles de croissance permettent la simulation informatique et la comparaison d'itinéraires sylvicoles (réaction aux éclaircies, interactions avec la ferle lité stationnent.). Des applications ont été réalisées pour divers peuplements (pins et hétrale-sapiniére en contexte montagnard-méditerranéen, plantatoins d'eucalyptus au Congo); d'autres sont en cours (pin maritime pour cies gestionnaires d'Aquitaine...).

International audience; Nitrogen fertilizer inputs increased sharply over the last decade in Brazilian eucalypt plantations. Due to the economic and potential environmental cost of fertilizers, mixed plantations with N-fixing species might be an attractive option to improve the long-term soil N status. A randomized block design was set up in southern Brazil, including a replacement series and an additive series design, as well as a nitrogen fertilization treatment. The development of mono-specific stands of Eucalyptus grandis (0A:100E) and Acacia mangium (100A:0E) was compared with mixed plantations in proportions of 1:1 (50A:50E), and other stands with different densities of acacia for the same density of eucalypts. The objective was to assess the effect of inter-specific interactions on the early development of the two species. Aboveground biomass was measured 6, 12, 18 and 30 months after planting, sampling 6–10 trees of each species per treatment at each age, and allometric equations were established in 0A:100E, 100A:0E, 50A:50E and 50A:100E. The height and basal area of E. grandis seedlings were enhanced by 12% and 30%, respectively by N fertilization at age 1 year. Inter-specific competition led to a stratified canopy, with suppression in acacia growth earlier for basal area than for height. The mean number of stems per acacia tree at 36 months after planting was significantly higher in pure stands (3.7), than in 50A:50E (2.7) and in the additive series (between 1.6 and 1.8). H/D ratios were highly sensitive to inter-tree competition for the two species. The suppressed acacia understorey in mixed-species stands did not influence biomass production and partitioning within eucalypts. This pattern led to biomass accumulation combining the two species in 50A:100E that was about 10% higher than in 0A:100E, from age 12 months onwards. Aboveground net primary production (ANPP) amounted to 25 Mg ha-1 and 37 Mg ha-1 from age 18 to 30 months in 100A:0E and 0A:100E, respectively. Acacia ANPP in 50A:100E amounted to 2 Mg ha-1 over the same period, as a result of substantial inter-specific competition. An increment in biomass production in these very fast-growing eucalypt plantations was achieved introducing acacia as an understorey and not in the 50A:50E design, as observed in other studies.

Models available to predict growth of forest plantations include: process-based, architectural and growth and yield models, each dealing with a particular aspect of the forest production. As a part of plantation sustainability research in Congo, these three approaches are being tested. Among them, the growth and yield model (EUCALYPT-Dendro) aims at: (1) assessing stand production under different silvicultural options, and (2) evaluating the risks of nutrient deficiencies for different harvesting strategies. This chain of models includes three modules: a single tree distance independent model assesses the tree and stand growth; a set of stem taper and biomass equations evaluates wood properties; and the biogeochemical module gives the within-tree content of nutrients (N, P, K). The simulation steps are at monthly intervals but seasonal variations are not yet taken into account. Growth and yield models such as 'EUCALYPT-dendro' are simple and are designed to explicitly take into account silvicultural practices and competition between trees. However, there is no real coupling between them and nutrient cycling models. In these models, 'site fertility' or 'site index' is generally defined as a dominant height at a given age. It is assessed from an inventory and is fixed for the whole simulation. This assumption is valid for forest ecosystems where there are only small changes in soil fertility within one rotation. However, in both temperate and tropical forests, fertility may change dramatically. Integrating nutrient cycles into growth and yield models could be a useful way to take into account such fertility variations, and provide a better basis for improved nutritional management of plantations. A growth and yield model and a procedure to incorporate nutrient cycling in such models is described. This procedure is discussed and compared with other approaches for modelling plantation growth. CIFOR's site management network is well positioned to provide data for evaluating a range of such models. Its structure and the large range of studied ecosystems would allow testing of the generality and robustness of the resulting models. An outcome would be a support decision system providing information on: (1) tree and stand growth, (2) silvicultural practices (thinning and fertilisation regimes), and (3) nutrient cycling. This information could be used by managers to assess volumes, biomass and wood quality of trees, and also for nutrient management decisions.

Eucalyptus tropical plantations are often established on poor soils, characterised by low reserves of available nutrients. Intensive silviculture (very short rotations) is carried out, resulting in the removal of large quantities of biomass, and leading to high risks of soil nutrient deficiencies. Within this context, a Cifor's network has been established to evaluate the impact of soil and slash management practices on the productivity of plantations (Tiarks et al., 1998). The core treatments created a gradient in the nutrient capital of each site, ranging from low levels (where all above-ground organic residues were removed from the plot, SMTO), through various steps to high levels of nutrient capital (where additional organic residues were distributed on the ground, SMT3). The objective of this work was to consider the whole growth trend (and not only a single year) in the data analysis. The main idea was to quantify how the following relationships were modified by treatments: stand dominant height as a function of age, stand basal area increment as à function of stand dominant height increment, and tree height as a function of tree girth. The method consisted in fitting these models for each of the considered treatment and to test the parameter variations with the type of slash management. For the dominant height growth, the speed to reach the asymptote (parameter b) was the only varying parameter across treatments. The observed pattern suggests that the dominant height growth response is of type 1 (Snowdon 2002), indicating that the slash management regime can reduce the time required for the stand to reach a given stage of maturity. The stand basal area response differed between countries: slash management effects were found to be completely transmitted throughout the dominant height growth in the Brazilian site (medium fertility), whereas there was an additional effect to be modelled in the Congolese site (low fertility). A slight trend was found for the South-African site but it was nonsignificant. The height-girth relationship was sensitive to slash management treatments. For a given age, trees in SMTO treatment (all slash removed) were smaller and shorter than in the other treatments. An additional operation was performed on the Congolese site where we tested the influence of slash management on the biomass and nutrient allocation (allometric relationship between tree size and biomass/nutrient concentration of each compartment). A difference between treatments has been observed for leaves and dead-branches biomass equations. But, in both cases, this result is probably a dominance effect rather than a slash management effect. By contrast to the biomass equations, nutrient concentration relationships were in most cases different between treatments (significant effect of the slash management on model parameters). Treatment BLO showed, generally, a lower nutrient concentration whatever the considered compartment.

International audience; Forest scientists build models to study, understand and represent stand growth and dynamics. They are particularly interested in the evolution of ecosystems, at the tree and compartment levels and in the consequences of forest management on volume, shape, wood quality, structural evolution of the stand or sensitivity to meteorological and sanitary problems. Specific computer tools are often developed to implement these models, to test and to explore the consequences of the underlying hypotheses on real or virtual stands. Sometimes, a team may invest in the development of a more integrated tool, based on a parameterisable growth model. The Capsis project aims at integrating several types of forest growth and dynamics models - stand models, distance independent or spatially explicit tree models,... - and providing forest management tools to establish and compare different silvicultural scenarios. The objective is to build a perennial, open and dynamic software platform (1) to contribute to the development of odels and test their sensitivity to some parameters by simulating the manager's actions, (2) to share tools and methods, (3) to compare results of different models, (4) to transfer models to the managers and (5) to serve as teaching material. Most models implemented in Capsis are described in a web database hosted by the European Institute for Cultivated Forest (www.iefc.net). Capsis is a portable software, designed around a kernel which provides an organizational data structure - session, project, scenario step. The kernel also proposes generic data descriptions - stand, compartment, tree,... These descriptions can be completed in modules - one for each model - which implement a proper data structure and a specific evolution function (growth, mortality, regeneration, dissemination,...) with a chosen simulation step. A plugin architecture provides the possibility to build tools for management, construction of graphics, data exportation, tree group construction, stand representation or connections with other software. At the present time, Capsis hosts six modules, several other integration projects are planned and model integration training sessions are periodically proposed.

Forest scientists build models to study, understand and represent stand growth and dynamics. They are particularly interested in the evolution of ecosystems, at the tree and compartment levels and in the consequences of forest management on volume, shape, wood quality, structural evolution of the stand or sensitivity to meteorological and sanitary problems. Specific computer tools are often developed to implement these models, to test and to explore the consequences of the underlying hypotheses on real or virtual stands. Sometimes, a team may invest in the development of a more integrated tool, based on a parameterisable growth model. The Capsis project aims at integrating several types of forest growth and dynamics models - stand models, distance independent or spatially explicit tree models... - and providing forest management tools to establish and compare different silvicultural scenarios. The objective is to build a perennial, open and dynamic software platform (1) to contribute to the development of models and test their sensitivity to some parameters by simulating the manager's actions, (2) to share tools and methods, (3) to compare results of different models, (4) to transfer models to the managers and (5) to serve as teaching material. Capsis is a portable software, designed around a kernel which provides an organizational data structure - session, project, scenario step. The kernel also proposes generic data descriptions - stand, compartment, tree... These descriptions can be completed in modules - one for each model - which implement a proper data structure and a specific evolution function (growth, mortality, regeneration, dissemination...) with a chosen simulation step. A plug-in architecture provides the possibility to build tools for management, construction of graphics, data exportation, tree group construction, stand representation or connections with other software. At the present time, Capsis hosts six modules, several other integration projects are planned and model integration training sessions are periodically proposed.

Since 1978, 42000 ha of clonal Eucalyptus plantations have been established in the littoral savannas of Congo, mainly for pulpwood production. These plantations were established on sandy soils, characterised by low reserves of available nutrients and a low water retention capacity. An intensive silviculture is carried out, resulting in the removal of high amounts of biomass and nutrients every 7 years. Therefore, a decision-making tool is needed (i) to assess stand productions under different silvicultural options, (ii) to evaluate the risks of nutrient deficiencies and non sustainable production, and (iii) to estimate the economic return of different harvesting strategies. For many years, field trials have been established focusing on clonal selection, silvicultural practices, stand growth and quantification of the biogeochemical cycles of nutrients. This high amount of data was used (or will be used) to elaborate a chain of models named "EUCALYPT-Dendro" that includes three main modules; - the growth module: a single tree distance-independent model was elaborated. The dominant height growth model is similar to the equation developed by Dhôte (1996). However, two main differences can be reported: (i) the model was segmented in order to take into account a change in height growth rate that occurs during stand rotation, (ii) tree spacing affected the dominant height growth and was introduced as regressor in the equation. The stand basal area increment is function of the dominant height increment. Individual tree basal area is function of a potential (given by the stand basal area increment) and a reductor (given by the size of the tree). The height of the trees is obtained from a height - girth relationship. Tree mortality is not yet taken into account (but in our case, tree mortality is limited owing to the short rotation length); - the tree properties module: a generic stem taper equation was constructed. It explicitly takes into account the global taper of the bole (when the trunk is assumed to be a cone), the but swell and the decrease in diameter within the crown. The equation allows accurate estimations of diameters and volumes along the bole. The wood density model was based upon a non-parametrical modelling approach but is not yet introduced within the chain of models. Allometric relationships were also fitted for evaluating the biomass of roots, branches, stem, bark and leaves throughout the whole rotation; - the biogeochemical module: a model was built to assess the distribution of nutrient concentrations (N, P, K) in individual rings within the bole and their changes with the ring ageing. Furthermore, different allometric relationships estimated the nutrient contents within the branches, roots, leaves and bark. Input-output budgets of nutrients at the plot level were simulated during the whole planted crop rotation from (i) measurements of nutrient fluxes in a clonal stand between ages 6 and 9 years, (ii) a chronosequence approach to quantify the main fluxes of the biological cycle throughout stand rotation, and (iii) hypotheses concerning nutrient losses by deep drainage during the juvenile stand growth. Work is in progress. All these models are embedded within Capsis (for the growth modelling part) and will be introduced within Win-Epifn (for the wood properties part and logging). Key points concerning the building of the models are presented. Input-output budgets of nutrients during the planted crop rotation are simulated to assess the influence of various silvicultural practices (spacing, rotation length, harvesting options) on the amount of available nutrients in the soil. Economical aspects are not evaluated.

L'objectif de cette mission était de prendre contact avec les chercheurs de l'UR2PI ainsi qu'avec la société ECOsa en charge de 42000 ha de plantations d'Eucalyptus à Pointe-Noire au Congo. Deux tâches ont été mises en route avec les chercheurs de l'UR2PI: l'analyse des données de croissance récoltées sur le dispositif de Jean-Paul Laclau et un projet visant à caractériser la fertilité des stations forestières (Jean de Dieu Nzila). Par ailleurs, dans le cadre de l'ATP-carbone, un protocole a été élaboré avec Olivier Roupsard pour mettre en place les placettes de mesures de croissance. Paul Bertaux (responsable aménagement d'ECOsa) est vivement intéressé par l'élaboration d'un outil d'aide à la gestion et met à la disposition de l'UR2PI la base de donnée de la société pour élaborer des modèles de croissance sur l'Eucalyptus. Cette base regroupe trois volets: les inventaires (non réguliers) des parcelles ECOsa (mesures depuis 1987), les inventaires des placettes permanentes (mises en place en 1998) et des mesures de défilement (environ 2500 arbres abattus pour élaborer des tarifs de cubage). Tous ces travaux avec PUR2PI et ECOsa ont pour objectif la construction un modèle de croissance pour l'Eucalyptus au Congo.

In this paper, the authors propose to assess the timber quality of a standing tree from usual forest inventory measurements such as tree age, height and diameter at breast height. Growth equations are used to reconstruct the past growth of a tree and to predict its current internal structure, namely ring distribution. These models are linked to allometric equations that estimate the characteristics of branches, to models that predict physical wood properties such as wood basic density from ring distribution and to a glass-log software that simulates the sawing and grading of any board located in a stem whose morphology is known in detail. The French Forest Inventory data for Norway spruce are available at three dates : 1973, 1981 and 1992 (C1, C2 and C3). One of the most important French districts for Norway spruce in France, the Vosges district, has been chosen. Between the first and second forest inventory, both forest area and total volumes have increased. Between C2 and C3, the forest area remains the same but the standing volume has increased consequently. In the second part of this paper the authors analyse, for the three dates, the stands dominant heights for the same stand age classes; the stand ages for similar breast height diameter classes; the timber properties for similar breast height diameter classes. In the last part, they discuss the possibility of taking into account the increase of fertility into a stand growth and wood quality model modelling approach