The WUEtree project focuses on "water use efficiency (WUE)" and the functional related traits because the challenge of many tree plantation programs, facing the global changes, is to improve the tree adaptation and the biomass production without increasing water extraction. The project responds to BIOADAPT in developing research on adaptation mechanisms and is situated at the interface of the two themes proposed by the call: “biological adaptive response of living organisms facing global change” and “methods and selection tools to adapt organisms to global changes”. WUEtree tests the general hypothesis that WUE exhibits significant variability within tree population and that it can be improved in breeding programs without compromising the biomass production. WUEtree aims at understanding the biological basis of WUE and its genetic and environmental determinisms. The ultimate goal is to define an ideotype and a selection methodology combining phenotypic and molecular information. To reach this objective we develop with a 36 month research program, through four scientific tasks (tasks 2 to 5) and one coordination and management task (task 1). The task 2 consists in understanding the functional relationship between WUE measured at leaf level (WI) and tree level (Wp) with ?13C and other related ecophysiological components (leaf traits, transpiration, etc..). It seeks to predict WUE at leaf and individual tree level using ?13C and related traits. The task 3 estimates the genetic and environmental variance components of ?13C and related traits and the correlations with biomass using quantitative genetic models. The task 4 is complementary to task 3 and seeks to understand, using association studies and fine mapping strategy, which genomic regions and which genes underlie ?13C and associated traits. In task3 and task 4 the genotype by environment interaction is evaluated using appropriate field designs showing different stress levels. The task 5 uses tasks 2, 3 and 4 information to test selection methodologies, such as genomic selection, associating both phenotypic and genomic data. The objective is to provide new statistical models to accurately rank genotypes. WUEtree is conducted with two tree model species, the hybrid Eucalyptus urophylla x grandis and Pinus pinaster, and relies on original experimental field trials established respectively, in the Republic of the Congo and in the south west of France. The expected results are a better understanding of the biological basis of WUE and of the genetic and environmental determinants. This new knowledge will be used for defining and selecting ideotypes presenting optimal WUE and productivity for marginal zones. The four partners, UMR 1134 AGAP CIRAD-INRA-SUPAGRO “genetic improvement and adaptation of tropical and Mediterranean plants”, its sub-contractor CRDPI “Centre de Recherche sur la Durabilité et la Productivité des Plantations Industrielles, Republic of the Congo”, UMR1137 EEF INRA-Université de Lorraine "Ecologie et Ecophysiologie Forestières”, UMR 111 Eco&Sols Montpellier SupAgro–CIRAD–INRA–IRD “Ecologie Fonctionnelle & Biogéochimie des Sols & Agroécosystèmes” and UMR 1202 BIOGECO INRA-Université de Bordeaux 1 “Biodiversité Gènes et Communautés” exhibit strong complementary skills combining genetics and biostatistics (AGAP/BIOGECO), tree ecophysiology (EEF/BIOGECO), process-based modelling (Eco&Sols/EEF), tree genomics and genome analyses (AGAP/BIOGECO) and field trial management (CRDPI/BIOGECO). The position of AGAP, Eco&sols and of BIOGECO in institutions associating research and companies involved in tree plantations (“Eucalyptus Fiber of the Congo” with the CRDPI), (GIS “Pin maritime du Futur” consortium funded by its memberships (INRA, FCBA, CRPF, CPFA and ONF), offers opportunities for the project to significantly impact the Eucalyptus and maritime pine breeding programmes.

Summary Tropical tree plantations provide indispensable renewable goods to the global market and family farms represent the majority of their surface area and production. To ensure the sustainability of plantation systems, environmental and socio-economic conditions should remain favorable during several decades. How can such conditions be ensured when the environment is changing? Even if the local consequences of global increase in temperature are difficult to assess, the farmers will probably face a more variable climate, with probable changes in rain patterns. Moreover, all natural resources have recently faced hugely variable prices related to variations in global demand. High prices attract new investors and drive the extension of plantations into new areas, inducing land-use changes and changes in farming structures. The final aim of the project is to analyze how smallholder’s tree plantations can adapt and keep sustainable whereas they face variable climatic conditions and deep changes in their socio-economic context. Do farmers perceive these risks and do they initiate adaptive strategies? Rubber tree-based systems in Thailand will be used as a model of tropical family plantations integrated in a major global commodity channel. The project will assess both the specificities of rubber cropping and the more general features of tree plantations. The originality of the project relies on the multi-disciplinary approach of both the characterization of changes and their consequences on rubber plantations and the related risks for farmers. Plant and soil sciences will be associated to social sciences and economics. We will analyze the way socio-economic factors interact with biophysical factors to determine farmers’ vulnerability or adaptability to changes. This will require the identification of relevant indicators to measure farmers’ adaptation, and the impacts of changes on sustainability and resilience of the systems. We will refer to the Sustainable Livelihood Framework (Ellis, 2000) to represent the household/holding , combined with the OECD risk matrix (2009) to assess households’ viability. We will focus on two major factors, (i) the type of holdings, particularly the emergence of new investors and (ii) the share-cropping contracts that frame the management of plantations. The main biophysical risk relate to climate changes and to the extension of plantations in new and more adverse areas. We will evaluate the risks at plot or farm levels, as well as potential externalities, in terms of soil sustainability (soil fertility preservation related to soil physical quality and soil functional diversity) and tree adaptation to water stress. Specific ecological constraints linked to the different cultivation area will be considered. In the North-eastern rubber extension area, the climate is drier and the soil fertility is low, whereas in the traditional area (South) continuous rubber cropping occurs for more than 50 years (third cycle). In the North, the specific issue of rubber installation in mountainous area will particularly focus on the effects of terracing, considering the impact on water flow and water balance. A typology of rubber farming systems and of practices will be proposed from socio-economic survey, particularly regarding land management and latex harvesting systems. The impact of practices on economic performances, soil physical and bio-functioning will be evaluated through specific indicators that will be developed or adapted in the perspective of multi-criteria evaluation of plantation systems. The information will be integrated at different scales from plot to farm and watershed and shared with stakeholder through a co-innovation platform. Beside the specific case of rubber plantations, a more generic output of the project is to determine, through modelling and risk framework analysis, the most significant indicators to be observed to assess the long-term adaptation and sustainability of tree-based family farms.

The effects of increasing global temperatures on soil biodiversity and the resulting effects on the coupling/decoupling of biogeochemical C, N, P cycles are poorly understood. This project attempt to assess the biodiversity and functional composition of soil microbial communities, including soil fauna (earthworms) and plant-soil interactions responses to soil warming using three whole soil warming experiments established in France, USA and China. We will focus our study on whole soil profiles, as in particular subsoil horizons may have a large temperature response to warming and could release carbon to the atmosphere as positive feedback mechanism. The information obtained through the data generated by our project will be used to benchmark an existing simulation model, which includes representation of soil depth, transport, and microbial physiology of functional guilds. The simulations outcomes can then support the formulation of policies to promote adaptation and mitigation strategy.