Distribution of small mammals in a pastoral landscape of the Tibetan plateaus (Western Sichuan, China) and relationship with grazing practices
Résumé
Small mammal distribution was studied along a grazing gradient in a pastoral landscape of the Tibetan plateaus of Western Sichuan, China. Smaller small mammals (< 100 grams) were sampled using standard trapping. The link between habitat and both smaller and larger small mammal distribution on a landscape scale was estimated using landscape transects. The relative density of the Microtus oeconomus/limnophilus complex ranged from higher levels in fenced grassland and bushes (i.e. low grazing pressure), to lower levels in habitats with a high grazing pressure, where this species was not trapped. Ochotona curzoniae, O. cansus and Cricetulus kamensis displayed a reverse gradient, with higher relative densities in overgrazed habitats (bare grounds). The distribution of Microtus irene was restricted to two slope habitats: rocky slopes and Stellera chamaejasme grassland. Microtus leucurus was only trapped in Potentilla fruticosa bushes and in a single grassland type, having an intermediate stage of degradation. These results suggest a differential response of the small mammal species, in terms of relative density, to grazing pressure level.