Shrubland as a soil and water conservation agent in Mediterranean‐type ecosystems

Abstract

John Thornes found that shrubland was a key factor in the control of soil erosion on Mediterranean hillsides. His research inspired many scientists to investigate the impact of shrubland changes and management in semi-arid ecosystems. An example of Professor Thornes’ scientific influence is the experiment carried out on the El Teularet–Sierra de Enguera experimental station since 2003 which showed erosion rates on a 30-year-old abandoned orchard with dense vegetation cover of Ulex parviflorus and Cistus albidus and a 20-year-old fire-affected maquia with Quercus coccifera, Pistacia lentiscus and Juniperus oxycedrus. The measurements demonstrated that the shrubs help create more stable soil temperature and to lower soil moisture content, whilst soil properties under the shrub cover showed a higher organic matter content, lower bulk density and higher soil water repellency. The two plots created have subplots of 1, 2, 4 and 16 m2, in which soil and water losses were measured. Those plots produced negligible runoff and sediment transportation during the very wet year of 2004 (715 mm rainfall). Rainfall simulation experiments at 55 mm h−1 during 1 h showed that even under 10-year return period thunderstorms, the patchy distribution of the shrubs is a key factor in controlling soil and water losses as they reduce the connectivity of the surface wash. These measurements confirm John Thornes’ idea that shrubland is an effective vegetation cover to control soil and water losses in Mediterranean ecosystems.