Predicting cover types in a mountain range with long evolutionary grazing history: a GIS approach.

CINGOLANI, A.; RENISON, D.; TECCO, P.; GURVICH, D.; CABIDO, M.

JOURNAL OF BIOGEOGRAPHY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2008 vol. 35 p. 538 - 551

0305-0270

Aim. To determine how distribution and cover of different vegetation types are affected by physical factors and livestock in a mountain range with a long evolutionary history of grazing. Location. Upper vegetation belt of the Córdoba mountains (1,700 to 2,800 m a.s.l., 31º 34’ S, 64º 50’ W) in central Argentina. Methods. Using GIS, we analysed the relationships of plant cover types with physical features (physiography and topography) and indicators of accumulated livestock pressure (distance to human settlements and roads) through multinomial logistic regression. We predicted a present vegetation map which was validated with a real map. We then constructed two maps simulating minimum and maximum values of accumulated livestock pressure for the whole area. Map comparisons allowed evaluation of the possible influence of livestock, both in extension and intensity. Results. Both physical features and livestock pressure influenced the occurrence of vegetation units. The overall accuracy of the predicted map at the pixel level was low (26 %) indicating low habitat specificity of the vegetation units. We interpreted that non-explained variance was owed in part to livestock pressure patterns not fully captured by our indicators. Our models proved quite adequate predicting total percentages of vegetation units at larger scales. The extrapolations showed that under a history of low livestock pressure such as in sites far away from human settlements and roads the area would be dominated by woodlands, tussock grasslands and natural rock outcrops. Under a history of heavy livestock pressure, in turn, rock exposed by erosion, tussock grasslands and natural rock outcrops would dominate. Main conclusions. Vegetation units showed low habitat specificity, and were associated with accumulated livestock pressure, indicating that livestock and its associated activities are important factors structuring the landscape, and have important consequences on the integrity of the ecosystem. Results suggest that, although this system evolved with large herbivores, it has experimented irreversible degradation processes, and intensification of current domestic livestock pressure will likely lead to even more land degradation.