Long Term Persistence of Dehesas. Evidences from History

Abstract

Dehesas are agrosilvopastoral systems characterized by a savanna-like physiognomy. Today the central problem for the continuity of the dehesas is the gradual decay of tree canopy. We have investigated the history of the vegetation and management of dehesas from the middle ages to the present day in order to know in which conditions they have persisted in the long run. The results show that the word dehesa has been used historically for private grazing lands, with no reference to any vegetation type. According with the resources used during the middle and modern times the vegetation was a mixture of grasslands, shrubs and trees. The first descriptions of the vegetation of SW Spain in the 18th century showed that open oak parklands were scarce, while oak shrublands were very common. After the privatization of the land in the 19th century large private farms called dehesas developed in SW Spain, that were devoted to livestock raising in combination with agriculture and forestry. The change in management practices favored open oak parklands over oak shrublands in the dehesas, becoming the dominant vegetation of these farms in the 20th century. Is in this moment when dehesa passed to mean open oak parklands devoted to grazing, cultivation and forestry. The effect of the change in vegetation structure and management practices on oak regeneration is discussed.