Fire history in western Patagonia from paired tree-ring fire-scar and charcoal records

摘要

Fire history reconstructions are typically based on tree ages and tree-ringfire scars or on charcoal in sedimentary records from lakes or bogs, butrarely on both. In this study of fire history in western Patagonia (47–48° S)in southern South America (SSA) we compared three sedimentary charcoalrecords collected in bogs with tree-ring fire-scar data collected at 13nearby sample sites. We examined the temporal and spatial correspondencebetween the two fire proxies and also compared them to published charcoalrecords from distant sites in SSA, and with published proxy reconstructionsof regional climate variability and large-scale climate modes. Two of ourthree charcoal records record fire activity for the last 4 ka yr and one forthe last 11 ka yr. For the last ca. 400 yr, charcoal accumulation peakstend to coincide with high fire activity in the tree-ring fire scar records,but the charcoal records failed to detect some of the fire activity recordedby tree rings. Potentially, this discrepancy reflects low-severity firesthat burn in herbaceous and other fine fuels without depositing charcoal inthe sedimentary record. Periods of high fire activity tended to besynchronous across sample areas, across proxy types, and with proxy recordsof regional climatic variability as well as major climate drivers. Fireactivity throughout the Holocene in western Patagonia has responded toregional climate variation affecting a broad region of southern SouthAmerica that is teleconnected to both tropical- and high-latitude climatedrivers-El Ni?o-Southern Oscillation and the Southern Annular Mode. Anearly Holocene peak in fire activity pre-dates any known human presence inour study area, and consequently implicates lightning as the ignitionsource. In contrast, the increased fire activity during the 20th century,which was concomitantly recorded by charcoal from all the sampled bogs andat all fire-scar sample sites, is attributed to human-set fires and isoutside the range of variability characteristic of these ecosystems overmany centuries and probably millennia.