Grazing and environment interactions in the forest-steppe complex of Southern Patagonia

WARDELL-JOHNSON G.; PERI P.L.; MUCINA L.; LASAGNO R.

Dunedin

Congreso; Southern Connection Congress; 2013

University of Otago

Grazing impacts have been particularly profound in high latitude environments such as in southern Patagonia. However, differential effects of grazing on different environments and on phylogenetic patterns remains unclear. We carried out a floristic (141 site x 275 species matrix using 1000 m2 quadrats) and environmental assessment (16 edaphic, 16 climate variables) based on four levels of grazing (undisturbed vegetation, low, medium and high stocking rate) across the environmental variation in southern Patagonia, Argentina. We sought to determine the influence of edaphic and climatic environment on the overall floristic pattern, and whether there was a differential influence of grazing across the three main vegetation types assessed (forest, shrubland, grassland). We found that grazing does not appear to have a controlling effect at the landscape level (all vegetation types, including wetlands considered), but it does show influence at the lower scales (distinction between woody and non- woody vegetation; partly also within the forests). Phylogenetic composition (i.e. total phylogenetic branch length) was considerably altered by grazing. Thus a possible regime shift is suggested in areas previously considered less affected by grazing ? the forests and shrublands in particular. Thus the total evolutionary potential of these environments is likely to be impacted by grazing, with significant implications for climate change adaptation.