Global warning consequences on importance of soil respiration components in the carbon budget of oil palm ecosystem

The general aim of this present work was to prospect the effect of the Global Warming on one of most important ecological parameter in any ecosystem for the Carbon Cycle: the Soil Respiration and its components. Carbon budget for oil palm plantations is of prime importance to diagnose its ecophysiological functioning and evolution and nowadays any prospectives in that sense is highly a fundamental political issue for oil palm extention and development. For oil palm, a planted ecosystem, several measurements in different ecologies -dry (West Africa) and wet (North Sumatra- Indonesia) - have permit to quantify the different components of soil CO 2 efflux and a specific spatial variation (Frond Pile, Windrows, Harvest Path, Trunk Circle) related to agriculture practices. The main components, composed by the roots respiration (Rr or Ar, Autotrophic Respiration), the root-free soil respiration (HR:Heterotrophic Respiration) the litter and fine litter decomposition as well as the root turn -over and the total carbon allocation to the root system (TBCA) could change under seasonal variations or other climatic events (El Nino/La Nina). These components are important for quantifying the carbon budget in natural and agricultural ecosystems and especially carbon caption. Soil respiration is strongly depending on soil temperature in interaction with the soil water content. Q w estimations were calculated as well as non linear regressions (Y= a Ln (SVWC) ¿ b: a, b parameters, SVWC: soil volumic water content) fitted to the data. To simulate C flux all over the year and for the different locations (frond pile inside a plantation, empirical relations were used as: C flux = f(T°C) g(SVWC), f and g as function depending on the ecology and on the location in a plantation, and then respectively for AR and HR. Net Primary Productivity (NPP) could estimated from growth, standing biomass, from annual production of aboveground material such as fronds and inflorescences, from the production of root biomass and root turnover. Carbon sequestration could be estimated by subtracting the heterotrophic component of respiration. Through an important set of climatic data in North Sumatra including soil temperatures, simulations of CO2 soil efflux and its components were done in regards to predict the evolution of oil palm ecosystem parameters as soil carbon content, root turn-over, total carbon allocation to the below ground compartment and possible consequences on oil palm carbon caption. In regards of the results, a better understanding of the below ground carbon compartment could be obtained as well as sustainable recommendations for better cropping practices. (Résumé d'auteur)