Limitations to plant establishment on eroded slopes in southeastern Spain

The possible causes for the lack of vegetation in five badland sites from southeast Spain were experimentally tested. The main factors affecting seed germination and seedling survival considered were seed availability, regolith water dynamics in relation to rain events, regolith salinity, seedling predation by herbivores and seedling removal by erosion. Four issues are addressed: 1. Both rainfall and the temporal and spatial dynamics of regolith water during the seedling emergence period were monitored in five different zones at one site (Petrer, Alicante). 2. Effects of salinity and water potential on the rate and speed of germination of local seeds were determined. 3. Seed reserve and seedling emergence and mortality were followed throughout one season. 4. Regolith characteristics of all five sites were compared and the consequences for plant colonization discussed. The main factor limiting plant colonization in these sites was the very short duration of available water in the soil, due to the physical and chemical characteristics of the regolith. In addition, high regolith salinity and its effects on seed germination, the aspect of the site and the pattern of rain events, played a very important role reducing germination and survival. Herbivory and erosion were seldom responsible for seedling mortality. However, there were no highly erosive rain events during the study period, although several have been measured during the past few years.