Different soil units were selected in southeastern Spain to investigate the effects of land abandonment on soil erosion under semiarid conditions. The study sites selected were a cultivated field (bare), a 3-yr-abandoned field (herbs), a IO-yl-abandoned field (Artemisia herba-alba Asso.), and two soil units covered with semi-native (Stipa tenacissima L.) and native (Pinus halepensis Miller) vegetation. Simulated rainfall measurements showed that the erosion and runoff increased after the land abandonment, but later erosion decreased owing to the influence of increasing vegetation. Runoff discharge (35%) and the erosion rates (334 g m(2) h(-1)) were high in the 3-yr-abandoned land in comparison with the other land uses. Cultivation promotes infiltration of rainfall; as a consequence, the runoff and erosion rates were greatly reduced. Under Stipa tenacissima and Artemisia herba-alba, site conditions were very stable because of the high infiltration rates in the vegetated patches (100% of the rain infiltrated) Pinus halepensis produced the best conditions of vegetation cover, brit the development of a hydrophobic surface layer resulted in a slightly higher runoff(l4%) and erosion rates (2 g m(2) h(-1)). Land abandonment under conditions of drought and overgrazing seems to promote soil degradation, thereby reducing the infiltration capacity from 55 mm h(-1) to 19 mm h(-1) and increasing the erosion rate from 0 to 334 g m(2) h(-1) 3 yr after abandonment. Ten yr after abandonment (Artemisia herba-alba cover) and under native (Pinus halepensis) or semi-native (Stipa tenacissima) vegetation cover, the site conditions were very stable, producing almost no runoff and erosion. The distribution of runoff and erosion was directly related to the spatial distribution of the vegetation. Vegetation cover was minimal immediately following cultivation, and subsequently the spatial variability increased after abandonment. The revegetation stages culminated with the establishment of Pinus halepensis, exhibiting low spatial variability in vegetation cover and runoff and erosion. rates. The greatest differences in runoff and erosion within each land use were found under Artemisia herba-alba, followed by Stipa tenacissima owing to their patchy plant distribution.
