Do domestic herbivores retard Polylepis australis Bitt. woodland

TEICH, I., CINGOLANI, A., RENISON, D., HENSEN, I. AND GIORGIS, M.A.

FOREST ECOLOGY AND MANAGEMENT

ELSEVIER SCIENCE BV

Año: 2005 vol. 219 p. 229 - 241

0378-1127

Herbivores are often an important factor hindering the recovery of woodlands. Browsing generally retards seedling andjuvenile tree growth, but the exact impact of herbivores is still controversial. The high mountain areas of central Argentinaconsist of a mosaic of Polylepis australis Bitt. woodlands and different grassland types which are grazed by large domesticherbivores. To contribute to the management of these ecosystems, we performed an observational and an experimental study. Inthe first, we measured P. australis browsing intensity and size structure in areas with sparse woodland cover under twotreatments. One treatment consisted of seven areas with high stocking rates, and the other consisted of five areas where livestockwere reduced to low or moderate stocking rates 6–7 years prior to our measurements. In the experiment, we planted P. australisseedlings in a heavy grazed and an ungrazed area and measured growth and survival during 6 years. Our observational studyshowed that livestock browse heavily on P. australis, but a reduction of livestock densities reduced browsing rates and changedpopulation size structure. The experimental results confirmed the high browsing rates, and showed that browsing negativelyinfluences survival and height-growth. Our data suggests that heavy grazing by domestic herbivores retard P. australis woodlandrecovery, but a reduction in stocking rates promote changes that can lead to an increase in P. australis density. An adequatelivestock management is therefore very important in the mountains of Co´rdoba.