THE ECOLOGICAL IMPACT OF CATTLE ON CAULESCENT ANDEAN ROSETTES IN A HIGH VENEZUELAN PARAMO

The impact of cattle on caulescent Andean rosettes was studied in the Paramo de Piedras Blancas, Venezuela. Cattle were introduced into the Andes by the Spaniards in the late 1500s, but probably did not affect this paramo until the 19th century. Cows feed on the leaves of one species, Coespeletia timotensis, as a diet supplement mainly during the dry season, but avoid other rosettes. Browsing is concentrated on the intermediate size-classes of rosettes, and seedlings and plants taller than 120 cm are less affected. Cattle stay mostly close to streams and swales, where groundcover is higher. Rosette foliage along these areas is intensely browsed. In the study, rosette cover on a browsed plot had dropped 37.2%. A moist, densely vegetated slope was also visited cows, which browsed rosettes there, but cattle avoided the steepest, blocky talus slopes. Animal traffic along the heavily utilized valley floor has caused the loss and thinning of the sheaths of dry marcescent leaves which remain attached to the stems of C. timotensis. Rosettes on the steeper, more inaccessible slopes and outcrops have not been affected. Several possible ecological effects of cattle predation on Andean rosettes are discussed.