Resumo

PETER, G et al. Variation in specific composition and cover in grassland exposed to various grazing pressures in the Monte Rionegrino. Phyton (B. Aires) [online]. 2012, vol.81, n.2, pp.233-237. ISSN 1851-5657.

In the western Monte Phytogeographical Province of Rio Negro, vegetation is a shrubby-grassland steppe, where plants are interspersed within a bare soil matrix forming "phytogenic islands". The objective of this study was to evaluate the specific composition and cover of the study ecological system under diferent grazing pressures. We selected areas with high, moderate and low grazing intensity at three sites. In each area we established five linear transects, where basal cover and all intercepted species were registered. Sites were arranged through a Principal Component Analysis using the Infostat software. We analyzed similarity between sites, considering basal cover and species present in islands and inter-islands, and in both situations together. Islands and inter-islands were separated especially by the presence of shrubby species. Exclosure areas showed a greater cover of Poa ligularis, litter and biological crusts, whereas intense grazed areas presented a greater cover of bare soil. Grazing by itself and diferent grazing pressures can modify the specific composition at an island and inter-island scale. Greater cover of biological crusts could help recovery of the study system.

Palavras-chave : Desertification; Vegetation islands; Grazing intensity; Bare soil; Arid zones.

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