Soil organic carbon evolution after land abandonment along a precipitation gradient in southern Spain

Abstract

Land abandonment is the dominant form of land use change in the Mediterranean over the last decades, and determines the soil organic carbon (SOC) evolution during the secondary succession following abandonment. However, the rate of succession strongly depends on climatic conditions and the extent to which these determine the SOC dynamics is largely unknown. The aim of this study is determining these dynamics along a precipitation gradient (1085-650-350mmyr−1) on noncalcareous rocks in southern Spain. Fields abandoned in different periods, as verified on aerial photographs taken in 1956, 1977, 1984, 1998, 2001, 2004 and 2009, were selected using a chronosequence approach. SOC was determined using a spectrometer, vegetation was described, and NDVI calculated from Landsat images. SOC and NDVI evolution were analysed subsequently. In the two wettest sites SOC increased after land abandonment until it approached a plateau. Mean accumulation rates were 0.11kgCm−2y−1 for the wettest and 0.06kgCm−2y−1 for the intermediate site. These sites reached the long-term state, similar to the stocks in (semi) natural fields, in c.a. 10 years (wettest) and c.a. 35 years (intermediate). SOC and NDVI followed parallel trends, so SOC stocks were mainly driven by inputs from vegetation. At the dry end of the gradient, where NDVI’s (<0.1) were very low, the SOC stocks did not respond to changes in NDVI for the 50 year period.