Estudi fitocenològic de les pastures de la Plana de Vic. II: comunitats terofítiques (Thero-Brachypodietea) i síntesi

Abstract

After a previous work dealing with perennial communities, we describe in this one the pastures and grasslands characterized by Mediterranean annuals, which occur in the Plana de Vic country. In this sub-Mediterranean basin, located between the eastern Pyrenees and the Mediterranean areas of north-eastern Iberian peninsula, therophytic communities are restricted to dryest places of the hills, normally settling on superficial soils. The study deals with the species composition, ecology, distribution and syntaxonomy of the communities. Although all the communities treated clearly belong to Thero-Brachypodietea, they are not very typical forms of such class because of the non-Mediterranean character of the area studied. The Brachypodio-Stipetum is a common association, which is diversified into two subassociations rather different in structure and physiognomy The typical one is a Stipa iberica grassland occuring on culminal spots or on sunny slopes, under dry and hot microclimates. In the subassociation euphrasio-centaurietosum therophytes are dominant, it appears in compact soils with a contrasted seasonal water regime. Sedetum micrantho-sediformis is a community dominated by Sedum species, settling on initial soils which occur on carbonated flat rocky surfaces. Finally, Helianthemetum guttati is the only calcifuge pasture in the area. It is mainly built by therophytes and is typical of flat surfaces on sandstones with a thin sandy soil. The communities treated in this work and in the preceding one are synthetized and discussed in an ending section, which includes a summarizing table (all species per all communities) and an idealized transsection through a typical hill.