Insights into Holocene vegetation and climate changes at the southeast of the Andes: Nothofagus forest and Patagonian steppe fire records

Ecosystem fire regimes are a consequence of interactions among fuels and climate. The reconstruction of past fire regimes is of great importance for studying past climate changes and controls. The aim of this study is to compare two charcoal and pollen records from the Nothofagus forest-grass steppe ecotone (50 degrees S) and the grass steppe (49 degrees S). We compare fire regime responses to local vegetation changes, and inferred variation on climate conditions between 49 degrees and 52 degrees S during the Holocene. Cerro Frias and La Tercera charcoal records seem to be sensitive to centennial and millennial timescales of vegetation and climate variability inferred for southern Patagonia. During the Pleistocene-Holocene transition and during the middle Holocene, forest patchiness provided fuel vertical and horizontal continuity favoring fire activity. In contrast, in steppe environments high cover of shrubs favored grass patchiness, impeding fire spread. Higher pollen richness and variability through time seem to be related to higher vegetation patchiness. Past fire regime variability at the eastern side of the Andes has been closely related to westerly moisture influence between 52 degrees and 48 degrees S. Southern latitudes have been influenced by polar air mass intrusions to the continent during the last 5000 cal. yr BP.