Abstract

MORICI, Ernesto et al. Structural differences between caldenal patches of the rangeland and its influence on the seed bank, in the province of La Pampa, Argentina. Agrociencia [online]. 2009, vol.43, n.5, pp.529-537. ISSN 2521-9766.

The use of grasslands in the Caldén forest dates from over 150 years ago, and was dominated by low-height forage species. Now vegetation is distributed in patches, due to the effect of grazing, namely: middle height (dominated by non-forage species), low (dominated by forage species) and the co-dominated. The aim of this work was to evaluate the differences in a few structural variables between patches and their influence on the seed bank in the province of La Pampa, Argentina. For this description in the gramineous-herbaceous structure, aerial cover was established, along with humus cover, soil proportion, cover by species, density of perennial gramineous and gramineous seed bank. The specific diversity and richness was established from the vegetation cover; for Diversity, the Shannon-Weaver index was used. We found that grazing affected the structural variables evaluated and had a repercussion on the seed bank. The vegetation cover reached its highest in patches dominated by non-forage species, while diversity and richness was present in patches dominated by lower forage and co-dominated species. In the seed bank of the patches of forages, there is abundant Stipa trichotoma, a perennial, non-forage species. If we add that grazing in Piptochaetium napostaense affects productivity, vigor and permanence of plants, we would be facing a spiral of degradation.

Keywords : Seed bank; caldén forest; cover; diversity; grazing.