Changing fire regimes in the temperate rainforest region of southern Chile over the last 16,000 yr

A high-resolution macroscopic charcoal record from Lago Melli (42 degrees 46'S, 73 degrees 33'W) documents the occurrence of forest fires in the lowlands of Isla Grande de Chiloe, southern Chile, over the last 16,000 yr. Our data suggest that fire activity in this region was largely modulated by the position/intensity of the southern westerlies at multi-millennial time scales. Fire activity was infrequent or absent between 16,000-11,000 and 8500-7000 cal yr BP and was maximal between similar to 11,000-8500 and 3000-0 cal yr BP. A mosaic of Valdivian/North Patagonian rainforest species started at similar to 6000 cal yr BP, along with a moderate increase in fire activity which intensified subsequently at 3000 cal yr BP. The modern transition between these forest communities and the occurrence of fires are largely controlled by summer moisture stress and variability, suggesting the onset of high-frequency variability in summer precipitation regimes starting at similar to 5500 cal yr BP. Because negative anomalies in summer precipitation in this region are teleconnected with modern El Ni (n) over capo events, we propose that the onset of El Ni (n) over capo-like variability at similar to 5700-6200 cal yr BP led to a reshuffling of rainforest communities in the lowlands of Isla Grande de Chiloe and an increase in fire activity. (C) 2007 University of Washington. All rights reserved.