IMPROVING TOPSOIL CARBON STORAGE PREDICTION USING A DIGITAL ELEVATIONMODEL IN TEMPERATE FOREST SOILS OF FRANCE

Spatial distributions of C pools in forest soils are difficult to esti mate because of their inherent spatial variability and because of lack of reliable data (C concentration and bulk density down to a sufficie nt depth). In southwest France, thick humic acid soils have developed from Quaternary silty alluvial deposits, Previous studies have shown t hat these soils have accumulated large amounts of organic C (OC) and t hat the regional distribution of C stores depends on both textural and climatic gradients. However, a significant part of C content variabil ity still remained at a more detailed scale. The objective of this wor k was to determine if the topographic situation also influenced topsoi l C storage, which would improve the accuracy of the prediction of org anic pools in forest soils. This work uses a digital elevation model ( 100 x 100-m grid) to calculate topographic attributes on a 6000-ha are a. The results suggest that slope is the main factor controlling varia bility in local C stores. This study shows that relating OC contents t o spatial available landform parameters that might influence OC distri bution, and combining them into spatial models, can provide a useful t ool to improve geographical prediction of this characteristic.