Spatial characterization of root reinforcement at stand scale: Theory and case study

We propose a new upscaling approach for quantify root reinforcement at the stand scale using the spatially explicit root bundle model (RBM) for describing pullout force-displacement behavior coupled with a model for lateral root distribution. The root distribution model was calibrated using data of two excavated soil profiles, and validated with measurements of root distribution along the scarp of an artificially rainfall-triggered landslide in a vegetated hillslope above the Rhine river in northern Switzerland. Results show that the model overestimates small root density (1–3 mm diameter), leading to an error in estimated maximum root reinforcement of about 28%. For comparison, the most commonly used model of Wu overpredicts root reinforcement by a factor of 3. The spatial variability of estimated maximum root reinforcement within the forest stand is high, ranging from 0 to 20 kPa. Most soil reinforcement by roots occurs close to the tree stem or in zones where root systems overlap. The new approach provides a detailed description of maximum root reinforcement on a slope, an essential element for the prediction of shallow landslides and the management of protection forests.