Disposición espacial de parches de Austrocedrus chilensis con síntomas de defoliación y mortalidad en el Valle 16 de Octubre (Chubut, Argentina) Spatial distribution of Austrocedrus chilensis patches with defoliation and mortality in Valle 16 de Octubre, Chubut province, Argentine

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In the Patagonian Andes of Argentina, Austrocedrus chilensis is one of the native tree species most affected by forest fragmentation, resulting in remnants stands surrounded by grasslands. We studied vegetation in the edges of stands of dense A. chilensis adjoining areas that were cut 10 years earlier, with special reference to A. chilensis regeneration, diversity, abundance and specific species distribution. We found that the original composition of the vegetation had been strongly modified, there was a high proportion of exotic herbaceous species in the edge. Diversity and abundance of woody species was superior in the core forest (p = 0.0289 and p = 0.0149), and so was the richness of native species (p = 0.0053) and regeneration of A. chilensis (p = 0.0408). On the other hand the abundance of herbaceous species was greater in the edge (p = 0.0197). During the first years of the succession, the forest in the edge area tends to retract.

Native forests in Chubut Province cover an area of 1,000,000 hectares, of which 133,000 hectares are considered suitable for timber production. Approximately 10,000 hectares of this productive forest area has been, or is currently, the object of some form of timber exploitation. Pure Nothofagus pumilio forests (known colloquially as "lenga" forests) make up the largest native forest area (90%) in the designated land. In 1992, specific norms were introduced requiring those who intend to extract native forest timber to present management plans. The management plans presented to the provincial forest authority were analyzed with the aim of assessing their actual effectiveness as administrative tools for promoting the sustainable conservation of forest resources. One of the main conclusions which needs to be highlighted is the remarkable lack of coordination between planning and execution. This arises from: 1) Deficiencies in the structural characterization and volumetric estimation of the forest; 2) Conflicts over resource use, and 3) Conflicts of interests between businessmen and the state.

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