Impacts of cattle on the South American temperate forests: challenges for the conservation of the endangered monkey puzzle tree (Araucaria araucana) in Chile.

摘要

Notwithstanding the increasing cattle activity on the South American temperate forests, its impacts on the forests regeneration are yet poorly understood. We investigated the influence of cattle on the regeneration of monkey puzzle tree (Araucaria), an endangered conifer of the temperate forests of Chile and Argentina, on properties of small landowners and of timber companies. In thirty-six 100x20 m plots, we recorded the number of seedlings and saplings from seeds and resprouts, the number of cattle dung pats and the density of parent trees. We used the cattle dung pats as a surrogate of cattle activity (the cattle intensity index, CAI). The regeneration was analyzed as a function of the CAI, land tenure regime, the study site, and the number of parent Araucaria trees. We used likelihood methods and model selection for data analysis. Overall, there was a negative exponential influence of the CAI on all response variables. In small landowner forests, even low cattle intensities caused regeneration to drop rapidly to zero, whereas in plots owned by timber companies regeneration decreased smoothly as the CAI increased. The CAI affected regeneration of Araucaria qualitatively by decreasing the ratio of sexual/asexual regeneration, which may lead to problems of genetic drift in the long-term. Our results suggest that conservation of a single species does not necessarily ensure its long-term persistence. It is necessary to protect the ecosystems in which the species grows and involve local stakeholders in the development of management strategies that reduce the impacts of cattle ranching.