Print PageIn an attempt to determine if abandonment of goat grazing is negatively affecting traditionally managed landscapes, we evaluated how short-term grazing exclusion affects the species composition, soil nutrient content, percentage of bare soil, primary production and biomass nutritive value and tannin content on protected pastures of the Canary Islands. Permanent exclusion and control plots were established in 2007 in Anaga Rural Park (Tenerife Island) and Valle Gran Rey Rural Park (La Gomera Island). The botanic composition was evaluated within a nested series of square quadrats (plot sizes were 0.01 m2, 0.1 m2, 1 m2, 10 m2 and 100 m2). The primary production of the herbaceous species was calculated by means of random harvests of 1 m2 of size, which were classified into grasses, legumes and “other families”, oven dried and dry weighted. After that we analyzed biomass nutritive value and tannin content. Percentage of bare soil was evaluated by the point-quadrat method in the 100 m2 plots. Mixed soil samples were collected at 0–10 cm depth and pH, Olsen P (mg kg-1), percentage of organic matter (%OM), available cations in meq 100-1 g (Na+, K+, Ca2+, Mg2+) were determined. Sampling was carried out annually in spring.
Results/Conclusions
Ordination analysis showed significant changes in species composition after short-term grazing exclusion. However, these changes were not detected at all the analyzed scales. Primary productivity tended to increase after grazing exclusion, but this effect depends on the year of study. No differences were detected in soil nutrient content, percentage of bare soil, and biomass nutritive value and tannin content. Scarcity of significant changes can be explained by the low grazing pressure of the traditional management system, the dominance of the climate over the effects of grazing on this non-equilibrium ecosystem, and the lack of potential vegetation propagule sources, determining that the studied variables require more time to reveal significant differences. Due to the important cultural and socioeconomic values of this pasture, we suggest monitoring of the studied area in order to guarantee a sustainable management for the maintenance and conservation of this ecosystem.
