Effects of topsoil treatments on afforestation in a dry-Mediterranean climate (southern Spain)
Abstract. Revegetation programs in semiarid areas are associated with a high level of sapling mortality. Therefore, the development of alternative low cost and low environmental impact afforestation methods that ensure the survival of seedlings is necessary for the effective management of Mediterranean forest environments. This study assessed the effects of five types of soil amendment on the success of afforestation processes. The amendments tested were: i) straw mulching (SM); ii) mulch containing chipped branches of Aleppo Pine (Pinus halepensis L.) (PM); iii) sheep manure compost from a wastewater treatment plant (SH); iv) sewage sludge (RU); and v) TerraCottem hydroabsorbent polymer (HP). We hypothesized that in the context of dry-Mediterranean climatic conditions, the use of organic amendments would enhance plant establishment and ensure successful afforestation. The results showed that afforestation success varied among the various soil amendment treatments in the experimental plots. The amendments had no effect on soil organic carbon, pH, or salinity, but the results indicate that the addition of mulch or hydroabsorbent polymer can reduced transplant stress by increasing the soil water available for plant growth throughout the hydrological year, and potentially improve the success of afforestation by reducing plant mortality.