Efectos de los disturbios generados por diferentes estrategias de manejo sobre los estratos vegetales de bosques de Nothofagus antarctica de Chubut, Argentina

Nothofagus antarctica is a species of the Andean-Patagonian forest with a wide distribution from the north of Neuquén to Tierra del Fuego. Although the N. antarctica forests are of great economic importance for the region, they are intensely affected nowadays by human activities such as grazing, firewood extraction, conversion into pastures and the replacement by coniferous plantations. These activities produce changes in the N. antarctica forest, mainly by the alteration of its original structure affecting the performance of the ecosystem as a whole, resulting in the loss of biodiversity. Since July 2008 up to May 2010 in the northwest of Chubut, Patagonia, we analyzed the effect of disturbances associated with different management strategies on species composition and structure of N. antarctica forest. The disturbances on N. antarctica forest considered in this study are derived from extraction of firewood by patches and landscapes, conversion of forests into pastures, forest fires occurred 15 and 25 years ago. Pristine forest was considered a control. The structure, composition and species diversity differ between forests affected by different disturbances. The higher arboreal and shrub stratum cover was observed in pristine sites (PR) while the largest herbaceous cover was observed in sites converted into pasture. The diameter at breast height (DAP) and the basal area (BA) of individuals of N. antarctica was larger than in those sites affected by firewood extraction at the landscape scale (FWL) than at the patch scale (FWP), while the density (number of individuals) was higher in the sites burned 25 years ago (B25). The canopy cover was higher in PR and FWL compared with those in the remaining sampling sites. Although some differences were found in the richness among the sampling sites, being higher in firewood extraction by patches and landscaped sites (FWP and FWL), there were no differences of diversity and dominance among sampling sites. Our results are compared with those obtained in previous studies in Patagonia and are of importance in the improvement of the management of N. antarctica forest and its conservation.