1) Lehrstuhl für Bodenkunde und Standortslehre, Universität München, Am Hochanger 13,

85354 Freising, Germany

2) Departamento Producción Animal (Agricultura y Economía), Universidad de Zaragoza,

Miguel Servet 177, 50013 Zaragoza, Spain

3) ZEBRIS Geoinformationssysteme und Consulting, Lipowskystr. 26, 81373 München, Germany, gruecker@zebris-geoconsult.de

Abandonment of degraded and marginal agricultural land is a widespread phenomenon in Spain and other Mediterranean countries. To study soil development and site dynamics a comparative investigation of field groups representing different ages of abandonment was realized in the Meastrazgo region of the Mediterranean province of Castellón. Analysis of soil samples for organic carbon and total nitrogen content and pH showed that a sufficient regeneration of organic matter is accomplished after 20 years of fallow. Contrary to this there is no buildup of 'available' phosphorus after abandonment. A fixation of phosphorus in unavailable forms in the first fallow years seems evident, and there is no reenrichment through solution or mineralization of organically bound P thereafter. Rates of soil erosion estimated through application of the Universal Soil Loss Equation are of medium to low intensity and range between 2,2 t/ha*a in the first fallow years and 0,6 t/ha*a after establishment of vegetation cover. Under grassland erosion is neglegible unless vegetative cover is destroyed through treading.

Keywords : land abandonment; soil regeneration; plant colonization; soil erosion; agricultural terraces; Spain

Mots clés : abandon des terres, régénération des sols, colonisation végétale, érosion des sols, terrasses cultivées, Espagne