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INRA
24, chemin de Borde Rouge –Auzeville – CS52627
31326 Castanet Tolosan CEDEX - France

Dernière mise à jour : Mai 2018

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Unité Biogéochimie des Ecosystèmes forestiers

Zone de texte éditable et éditée et rééditée

Description of the Biogeochemical Cycles in Forest Ecosystems Unit (BEF)

04 July 2012

The ‘Biogeochemical Cycles in Forest Ecosystems’ Unit (BEF) is an INRA research unit. BEF occupies an original position at the interface between geosciences and agronomy. It provides a sum of knowledge and a unique expertise in the domain of quantitative and functional ecology applied to biogeochemical cycles of forest ecosystems. BEF developed since 1998 a strong partnership with CIRAD leading to high-tech researches in tropical forest ecosystems and to the possibility of developing generic approaches.

Research and Innovation

This knowledge and this expertise are based on studies which combine different spatial (soil to standing trees) and temporal scales (from week to several decades) to understand the functioning of forest ecosystems. Thanks to the identification of fundamental processes and their drivers (eg. on organic matter mineralization, soil minerals weathering, atmospheric deposition, soil solution transfer and chemistry), this team is able to provide practical solutions for optimizing forest management in a changing environment (climate, land-use change, high pressure for wood supply). The unit is well involved in modeling activities mainly on plant growth and soil-plant interactions, soil carbon storage and soil organic matter dynamics. One of the strength of BEF unit lies in the set up of numerous instrumented and experimental sites in both temperate and tropical areas and monitored on the long term for flux measurements and environmental budget calculation. This approach is often supported by stable isotope multi-tracing to track interactions between nutrient cycles. The unit uses up-to-date equipments perfectly adapted to these researches (for example in lab: X-ray diffractometer, ICP-MS, ICP-AES, and now GC-LC IRMS; or in situ: soil gazes and lysimetric devices).

Flagship operations

Currently, the BEF unit is running 3 experimental sites in the north-eastern part of France (Azeraille and Grand-Pays on soil compaction, Breuil combining the species composition and fertilization regimes, Montiers which will combine soil gradient, slash management and water regimes) and two tropical sites in collaboration with Cirad (Congo and Brazil, eucalyptus plantations impacts on the environmental budgets). Each of these sites represents an open area for multidisciplinary researches; Breuil and Montiers will part of the core LTO’s of the LABEX and their description is given in the Joint Research Facilities.

The Congolese site, which is an example of close collaboration between CIRAD, INRA-BEF and INRA-EEF hosts a comprehensive experiment on biogeochemical cycles in Kondi (11°54'27.99"E, 4°34'21.19"S) including lysimeters, one flux tower and several field trials on eucalyptus growth, water and nutrient use efficiency. This site aims to evaluate the impact of land-use changes (from savannah to eucalyptus) on the environmental services. Moreover, it represents a model case study on fast growing species with very short rotations. We develop process-based research on carbon, water, nutrient cycling and their interactions at the site and landscape levels through data analysis and models. This site provided more than 30 papers in peer-reviewed journals on : production (biomass equations, Saint-André et al., 2005; root growth, Thongo et al., 2008), carbon sequestration (CO2 fluxes from the soil, Epron et al., 2004, Nouvellon et al., 2008; root respiration, Marsden et al., 2008, Thongo et al., 2010; soil carbon stock changes, d’Annunzio et al., 2008), Leaf-Area-Index and specific leaf area (Nouvellon et al., 2009), and nutrition and biogeochemical cycles after afforestation of the savanna (Laclau et al., 2003a, 2003b, 2005, 2009, 2010).

Research Programs

During the last 10 years, our researches focused on the characterization of the biogeochemical cycles in forest ecosystems, on the quantification of their main components and the fluxes between these components (see the conceptual model provided by Ranger and Turpault 1999). These researches provided insights in terms of nutrient budgets and their variability among forest ecosystems. They improved our knowledge on some processes (ex biological control of mineral weathering in the rhyzosphere, species impact on nutrient cycles, water and nutrient uptake by the vegetation), and led to innovative propositions to forest managers.

For the coming years, our research is focused on the soil plant interactions and their modeling. We started ambitious multidisciplinary programs on (i) the soil compaction and its impact on soil gazes and soil solutions, (ii) the fate of Ca and Mg in forest ecosystems using stable isotopes multi-tracing experiments, (iii) the processes of stabilization and destabilization of the organic matter using up-to-date technologies (GC-LC IRMS, in collaboration: STXM-NEXAFS, NanoSims), (iv) the development of a new generation of growth and yield models including biogeochemical cycles, (v) the functioning of the rhizophere using the emerging principles of functional microbiology, (vi) the atmospheric deposits and their contribution to the sustainability of forest ecosystems.

Valorisation / Exploitation of results

All these researches provide both scientific papers in well recognized journals (1st quartile in each discipline – Geosciences, Soil science, Ecology, Forestry and Agronomy –eg SSAJ, SBB, Ecology, Ecosystems, Forest Ecology and Management). The team also produces technical reports and papers for forest managers and decisions makers. During the last 12 years, the number of publications in peer reviewed journal was 179 (total citation 1,967) representing about 1.7 paper/researcher/year (and 2.4 paper/researcher/year for the last 5 years). Statistics for the period 2006-2010 is given in the figure below (64% of the 96 papers are in the first quartile and 24% are published in journals of IF>3). All these researches are also well transferred to the forest managers and for example, our collaborations with ONF (Office National des Forêts, the french National Forestry Agency) includes the hosting of one forest engineer during 3 years in the lab (M. Nicolas is now in the R&D department of ONF), collaborative research programs (on soil compaction, generic models of tree biomass and nutrient concentration – ANR EMERGE, site index and biomass estimates from Lidar campaigns – ANR FORESEE), and punctual expertise of specific questions. We also contribute regularly to large public conferences (ex: fête de la science, FIG-festival international de Géographie), to the press release as well as to interviews of radios (RFI, France Bleue, etc..). Our experimental sites are also the supports for visits from different audience (schools, forest managers, regional policy makers..)

Enseignement superieur / Higher education

Researchers are also deeply involved in training courses in doctoral schools (Nancy, Poitiers, Strasbourg) or schools of engineer (AgroParisTech, NFZ) on nutrient cycles in forest, soil acidification, mineral weathering, organic matter mineralization. They also co-organize thematic schools (such as “Philllosilicates in the soils” or “Models for Organic Matter Dynamics”). This represented for the period 2006-2010 an overall sum of about 100 hours/year of teaching. The unit hosts also several students from DUT to PhD levels, of France but also European and overseas countries (ex: Congo, China, Madagascar, Brazil).

Organisation

BEF regroups 7 researchers (on being common with IAM team), 9 technical and 3 administrative staff. Key persons involved in the LABEX project: Dr. Laurent Saint-André, the head of BEF team, is also in charge of the scientific coordination of the SOERE F-ORE-T (National network of long term experimental sites); Dr Laurent Saint-André is specialized in growth and yield modelling of tropical and temperate tree species including biogeochemical features to assess both production and sustainability of even-aged forests. He is involved into two international networks: Cifor’s Network on the slash management (Brazil, Congo, South-Africa, Indonesia, India, Australia) and the Rubber, Wood, Cropping, Research (Thailand, Malaysia, Indonesia, Cambodia). Teaching in modelling and sustainable management of forest ecosystems. He participated to and coordinated WP’s of three research European project in Africa (West African Teak, CarboAfrica, Climafrica). He also coordinates the SOERE F-ORE-T (National network of long term experimental sites).