Responses of plant functional groups in grazed and abandoned areas of a Natural Protected Area

This work seeks to address several questions: Do plant functional groups respond differently to grazing? Can we use plant functional groups as tools for management, to support production and conservation efforts on the Canary Islands?We studied the effect of goat grazing on the contribution of frequency of several plant functional groups on a Natural Protected Area. To measure the contribution of frequency of seven functional groups between 2001 and 2005, a total of 36 permanent point quadrat transects were selected randomly in grazed and abandoned areas at the study sites. There were three types of responses: groups that did not respond to grazing (grasses and, with regard to origin native, alien and endemic groups), groups that showed on average a significantly higher contribution of frequency in grazed areas (herbaceous legumes and non-legume forbs) and groups that decreased in these areas (shrubs). Goat grazing has a significant effect on vegetation structure in the study area, increasing the contribution of frequency of the functional groups necessary for the maintenance of grazing. How some functional groups respond to grazing depends on inter-annual climatic variability. Therefore, assessing the effects of goat grazing on ecosystems requires a long-term approach.