Abstract

This study aims at identifying forest areas affected by surface erosion in Catalonia. It analyses the characteristics of forests that are related to erosion occurrence. The data on erosion observations and stand variables were obtained from the Third Spanish National Forest Inventory (2000-2001). We used the classification tree method to study the presence-absence of surface erosion in four different forest types, pure coniferous, pure broadleaf and mixed stands as well in forested semiarid areas. The method provided a description of the site and stand variables, which are associated with the occurrence of surface erosion. The results revealed that forest type and stand structure are strongly related to the probability of surface erosion occurrence. In pure broadleaf forests, surface erosion occurrence was greater in dense stands, whereas in pure coniferous pine forest, the erosion occurrence was greater in sparse stands. Surface erosion occurrence was the highest in stands dominated by Fagus sylvatica and Abies alba. In order to estimate the erosion probabilities of stands, we converted the results of the classification tree analysis into erosion probabilities and mapped forest areas as low, moderate or high surface erosion risk. The accuracy of the erosion probabilities was assessed using the ROC curve, which gave a fair level (0.75) of accuracy for the total classification tree, the best (0.78) for pure broadleaf and the lowest (0.66) for mixed forest. The results of this study can be applied in future forest management planning aiming to reduce erosion risk in forests.