Efecto de la orientación geográfica y el movimiento del ganado en la biodiversidad de los pastos de montaña del Parque Natural de Aralar

Abstract

Mountain pastures of the Natural Park of Aralar (Gipuzkoa, Basque Country, Northern Spain) are communal grasslands grazed in summer by sheep ('latxa' breed), cattle and horses. Animal pressure has promoted the reduction of the natural potential vegetation (beech forest) and the maintenance of herbaceous grasslands for centuries. Nowadays, the preservation of biodiversity is one of the main priorities in this Natural Park, in addition to the conservation of the human activity in the área. The aim of this work was to determine the effects of aspect and herd movement on the structure of the grassland herbaceous community. Three different áreas were chosen (North, South and South-east) and four zones in each one (hut, extensive, water point and nap zones). Randomly thrown quadrats (0,5 x 0,5 m) were used (10 quadrats/repetition, 3 repetition/zone) and the presence and cover of the species was noted in each case. Different diversity indexes were calculated (richness, Shannon's and Simpson's Índices) in order to assess community structure. In all zones, the most common species were Agrostis capillaris, Festuca gr. rubra and Trifolium repens. Species richness was similar in the different áreas in relation to aspect, however, species richness and diversity changed in relation to the animal activity being lower in the zones with greater activity (higher grazing pressure) where the percentage cover of A. capillaris and F. gr. rubra were higher. Simpson's diversity index was the most sensitive and the best to reflect the differences due to the studied factors.