Space-time distribution of geomorphic micro-environments in sloping abandoned fields (Aisa Valley, Pyrinees)

Abstract

The prevailing geomorphic micro-environments are studied on mountain abandoned fields, as well as their temporal and spatial distribution. Starting from geomorphic transects, the importance of different processes has been tested. The spatial variability of the geomorphic micro-environments is basically explained by the age of abandonment. During the ten first years severe sheet wash erosion processes prevail: between 10 and 25 years the importance mild sheet wash erosion processes increase: between 25 and 50 years no erosion areas prevail: and,finally, in the fields abandoned more than 50 years ago, the more active and degraded micro-environments (rills, stone pavement) prevail. In their three first stages, the evolution is controlled by the progression of plant colonization and by the installation of a dense shrub cover between 25 and 50 years. The evolution towards more degraded stages can only be explained by the sudden destruction of such plant cover, probably due to the management of abandoned fields.