Plant production along a grazing gradient in a semiarid Patagonian rangeland, Argentina

M. VICTORIA CAMPANELLA; ALEJANDRO J. BISIGATO; C. MARIO ROSTAGNO

PLANT ECOLOGY

SPRINGER

Lugar: Berlin; Año: 2016 vol. 217 p. 1553 - 1562

1385-0237

Patagonian rangelands havebeen grazed by sheep since early twentieth century. However, there is still adegree of uncertainty regarding how production of grass and shrub species changesalong a grazing gradient. The study was undertaken in Northeastern Patagonia, Argentina. Thecharacteristic vegetation in the area is a mosaic of herbaceous steppe withshrubs (HSS) and shrub steppe (SS). Grazing intensity was estimated throughsheep paths density. Individual plant production and plant density were used todetermine grass and shrub production per unit area, in both plant communities overthree years. Community production was obtained as the sum of grass and shrubcomponents. Differences were explored in shrub and grass production amongcommunities and years, and linear regressions between sheep paths density andthe proportion of each plant community along the transect were performed. Mean communityproduction was lower in SS than HSS, shrubs did not compensate for the declinein grass production in spite of the increase in shrub density. SS presented thehighest community production in the most humid year while HSS production peaks inthe year of average precipitation. We found that as the number of sheep pathsincreases (i.e. higher grazing intensities) the SS community replaces HSS, resultingin a reduction of forage for sheep. The results showed that changes invegetation structure as a result of grazing strongly influenced above-groundproduction. Results also indicate that the response of vegetation to changes inannual precipitation is community specific.