Grazing effects of ungulates in a Galician oak forest (northwest Spain)

The effect of roe and red deer on an oak forest in Galicia studying the vegetation (floristic composition, nutritive value and biomass) in an established enclosure and outside is described. A decrease in number and biomass of the species was generally observed outside after 3 years due to the pressure of grazing, although species like Erica arborea nearly doubled its biomass outside in three years, confirming the sometimes favouring effect of grazing. However, other desirable plants for these ungulates, like Rubus sp., Agrostis capillaris, Vaccinium myrtillus and Hedera helix decreased in biomass. The seasonal pattern in productivity and floristic composition is shown, as well as the decrease in nutritive value (protein and in vitro digestibility) by an ageing of vegetation due to the effect of grazing. A decrease in the number of species has also been observed after 3 years with posterior stability in floristic composition.