ABSTRACT According to the FAO (2012), agriculture is responsible for 14 percent of global greenhouse gas emissions. Agriculture suffers the impacts of climate change, but “agriculture has the potential to be an important part of the...
moreABSTRACT According to the FAO (2012), agriculture is responsible for 14 percent of global greenhouse gas emissions. Agriculture suffers the impacts of climate change, but “agriculture has the potential to be an important part of the solution, through mitigation” as recognizes IPCC. Agroforestry (AGF) systems are known to sequester C into aerial biomass, but also play an important role by enhancing C inputs into deep soil horizons. AGF trees have often a deep rooting system, due to the competition with the annual crop (Mulia and Dupraz 2006). C inputs from roots (turnover and exudates) may constitute an important part of SOC as they are easily stabilized through different processes (Oelbermann et al. 2004; Rasse et al. 2005; Peichl et al. 2006). ECOSFIX project aims at studying ecosystem services of shallow and deep roots such as hydraulic redistribution, C sequestration and soil fixation in different ecosystem structures and climates (Costa Rica, Laos, France). This work focusses on the experimental device that was implemented in an intercropping system at Restinclières, France in 1995 (durum wheat and walnut (13x8m)). A huge pit (5m long, 4m deep) was dug into the soil, perpendicularly to a tree row. Fine root impacts (< 2mm diameter) were counted on each trench walls, cubes of soil (1 dm3) were sampled at different depth and a model of root length density (RLD) from root intercept counts was established (Maurice et al. 2010). It well fitted (R2=0.59). This method allowed estimating root density through the profile, which was surprisingly homogeneous, down to a depth of 4 m and across the cropped alley. Soil cylinders were collected to measure C content, bulk density, penetrometry and soil C fractionation. Roots were sampled at different depths to be chemically analysed and study root traits. 16 minirhizotrons and Tª sensors were implemented in the pit at different depths and distances from the trees, to estimate fine root turnover of walnut trees. Images are collected every three weeks. 3 other 1.5 m deep pits were dug (in AGF, agriculture control and forestry control), and litterbags containing fine roots were installed at different depths before the pits were filled up. Chemical composition changes and mass loss will be analyzed after one year to determine the decomposition rate. Root C input into the soil was also modeled with the Hi-sAFe model.