Vegetación de las intercalaciones básicas de la provincia de Cáceres (Extremadura-España)

Laburpena

In a province with a predominance of siliceous rocks, slates, granites and pliocene sediments, there are large basic intercalations formed of Cambrian, Carboniferous and Miocene limestones, together with diabasic dykes, accounting for the presence of a particular kind of flora and vegetation that varies considerably from the surrounding types, above all in the more degraded stages. In the light of such a situation, in recent years we have been interested in carrying out a detailed study of these ecotopes that provide a refuge for both taxa and communities whose distribution until now has been circumscribed to areas of the Mediterranean coastline. The presence of similar plant biocenoses in the Portuguese-Extremaduran province(s) has enabled them to become enriched with some taxa from this province; in turn they have lost some of the more thermophilic ones. Examples of these are rupicolous communities of Asplenio ceteri-Cheilanthetum acrosticae or the tuffs of Carthamo lanati-Onopordetum macracanthü. In the present work we also conducted a biogeographic survey of the Toledano-Tagano sector, delimiting the subsector and district units into which is it divided and placing special emphasis on the units that wholly or partially belong to the province of Cáceres. The bioclimatic study of the the areas studied have allowed us to discover the bioclimatic stages and levels where the basic intercalations are situated from the values of It (thermicity index), the Ppa (period of plant activity) and Psub-0 (period with temperatures below zero). All the basic areas are located in the middle and lower mesomediterranean bioclimatic stage. The ombroclimatic data revealed that the territories studied feature an ombroclimate ranging between the medium dry to the lower subhumid. The phytosociological study points to the existence and permits an inventory of thirty-four associations and several subassociations, of which Carthamo lanati-Onopordetum macracanthü is described for the first time. Comments are also offered on two plant series; one of them climatophilic Pyro bourgaeanae-Querceto rotundifoliae sigmetum, a toletano-tagana basiphilic faciation with Quercus coccifera and another that is edaphophilic: Aro italici- Ulmeto minoris sigmetum.The phytosociological study was preceded by a floristic analysis in which some 650 plants were recognized, most of them deposited in the SALAF, SALA and MAF Herbariums.