Resumen

DE VILLALOBOS, Ana E. Efectos de los caballos cimarrones sobre la composición florística y la estructura de los pastizales naturales en las Sierras Australes Bonaerenses. Ecol. austral [online]. 2016, vol.26, n.3, pp.264-274. ISSN 1667-782X.

The objective of this work was to evaluate the effect of the presence of feral horses on the specific composition and functional structure of the natural grasslands of the Sierras Australes of the Pampean Region. I compared the species richness, diversity, evenness and functional composition between grasslands with contrasting grazing histories. The grazing history significantly affected all the variables evaluated. The grasslands closed to feral horses had higher richness, diversity and evenness, and recorded lower proportion of bare soil and exotic plants cover than the grasslands grazed by feral horses. The functional structure also was affected for the presence of feral horses. Shrubs and plants with strategies that permit to avoid grazing were more abundant in grazed grasslands, while that those areas closed for horses recorded more cover of annual and perennial tussocks grasses. The differential arrangement of experimental plots determined different plant associations consistent with the grazing history of the different study areas. Therefore, the presence of feral horses can be expressed in modifications in the condition of the system with the advance of species resistant to the grazing in replacement of perennial grasses that could be resulting in an irreversible degradation process.

Palabras clave : Grazing; Functional groups; Diversity; Species richness; alien plants.

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