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

Abstract

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