MONITORING VEGETATION CHANGES UNDER CONTINUOUS SHEEP GRAZING IN NORTHEASTERN PATAGONIA

ROSTAGNO, C.M.

Buenos Aires

Simposio; CST-COP 9- UNCCD. Understanding Desertification and Land Degradation Trends.; 2009

Comitte on Science and Technology (CST) COP 9 UNCCD

Abstract: The grass or grass with scattered shrubs steppes of the Punta Ninfas area in northeastern Patagonia are ecosystems with a high production potential for sheep grazing that in many places have largely been replaced by shrub steppes and their soils have been eroded. Livestock grazing has been considered the main cause of these changes. In the autumn of 2003, 5 exclosures were established to assess the natural recovery of the degraded areas. In each exclosure as well as in an adjacent area, 3 fixed plots were established to assess changes in the perennial vegetation cover in each of three different states of a state-and-transition model: two stable states (a “functional” grass and a “dysfunctional” shrub steppe, respectively), and a transitional state. During the period 2003-2007, with annual rainfalls close to the long term average, no changes in perennial vegetation cover were detected, either in the exclosure  or in the grazed areas. However, by the end of 2008, a significant decrease in vegetation cover, mainly perennial grasses, was recorded at the end of the growing season in the 3 states of the grazed areas as compared to the exclosures. The extended drought (end of 2007-2008) would explain the decrease in perennial vegetation cover under grazing conditions.