Mediterranean-climate oak savannas: the interplay between abiotic environment and species interactions

Accepted 13 May 2009 Copyright © EEF ISSN 1399-1183 Mediterranean savannas are landscapes with a continuous herbaceous cover and scattered trees. Savannas are usually intermingled with patches of woodland, shrub-land, treeless grasslands, and crop-lands forming a complex mosaic. Heterogeneity in topography, soil and climate, interactions among species, and the superimposed selective activity of wild and domestic herbivores, in addition to human activities such as clearing, ploughing and burning are main agents forging this type of landscape. Oaks are the dominant trees in the wooded pastures (called dehesas or montados) of the Iberian Peninsula (west Mediterranean Basin) and in the savannas of California (northwest America). However trees and shrubs belonging to many taxonomic groups may form savannalike systems in other regions with Mediterranean climate. These include Juniperus sp. and Retama sphaerocarpa in Spain, Pistacia atlantica and Ceratonia siliqua in north Africa, Acacia caven in Chile, other Acacia species in central Africa, Protea nitida in south Africa and Eucalyptus sp. in Australia. Interactions between the two contrasting life-forms, trees and herbs, in savannas may be synergistic or antagoReview