Soil–plant relations in Mediterranean forest environments

Abstract

During recent decades, Mediterranean forest ecosystems have been subjected to natural wildfires, as well as to important changes in land use. One of the main changes to the landscape has undoubtedly been the reforestation of marginal croplands (Pardos et al. 2007). Soil organic matter has a direct influence on soil conservation, water storage and fertility, and therefore is also an important factor in the perturbations and changes. Many studies in recent years have focussed on soil C dynamics within the context of global change (Bravo et al. 2008). Thus, soil fractionation (e.g. Knicker et al. 2006; Rovira and Vallejo 2007), microbial community (e.g. Zornoza et al. 2009) and biochemical parameters (e.g. Miralles et al. 2009; GonzalezPerez et al. 2008) have been widely studied in different types of forests and under various environmental conditions. The influence of changes in quantity and quality of soil organic matter on water repellency and aggregate stability is also important (e.g. Arcenegui et al. 2008). To predict hydrological functioning under different environmental scenarios, numerous experimental plots have been established in recent years, particularly in Spain, where such plots have been established in contrasting environments ranging from areas with a semi-arid Mediterranean climate to high Pyrenean mountains, mid-altitude mountains and Dehesa environments (i.e. Garcia-Ruiz et al. 2008; Gonzalez-Perez et al. 2008; Hernandez-Santana et al. 2008). Dehesas (with 3–5 million ha, located in dry regions of south-western Europe with poor acidic soils) are the most extended agroforestry system in Europe. They are multipurpose agrosilvopastoral systems with extensive land use, where apart from native grasses, Mediterranean shrubs and periodical crops are combined with widely spaced and scattered oak trees, which forms an open permanent upper storey (tree density from 10 to 80 trees per ha, depending on its main use). Nowadays, Dehesas are considered as habitats to be preserved because of the high biological diversity they include. In Mediterranean countries, the negligible commercial value of forestry products means that aspects such as protection against desertification and conservation of the diversity of flora and fauna assume a relatively more important role. In this context, several species-specific models have been developed for accurate assessment of the suitability of a territory for reforestation (Rubio and Sanchez-Palomares, 2006). However, in some Mediterranean areas where forest growth is high, fast-growing species, such as Eucalypts, pines and other species are now dominant. This implies improvements as regards water regulation and soil protection against erosion. However, the export of large amounts of nutrients as a consequence of forest establishment has also led to the need for studies to assess the sustainability of different models of this type of silviculture (i.e. Merino et al. 2005; Blanco et al. 2005). The Sociedad Espanola de Ciencias Forestales (SECF: Spanish Society for Forestry Sciences) was established in 1991. The Ecology, Ecophysiology and Forest Soil Study Group (one of 19 SECF Study Groups) held its most recent meeting on 22 and 23 October 2007, at the University of Salamanca. The meeting included a large variety of topics: soil chemistry, physics, microbiology, carbon flows, fertility, amendments, biogenic cycles, allelopathy, ecological modelling, silviculture treatments, forest fires, etc. A. Rubio (&) A. Blanco Ecology and Soil Science Unit, ETSI Montes, Polytechnic University of Madrid, 28040 Madrid, Spain e-mail: agustin.rubio@upm.es