A 1000-year record of forest fire, drought and lake-level change in southeastern British Columbia, Canada

Abstract

High-resolution charcoal analysis of lake sediments and stand-age information were used to reconstruct a 1000-year fire history around Dog Lake, which is located in the montane spruce zone of southeastern British Columbia. Macroscopic charcoal (>125,um) accumulation rates (CHAR) from lake sediment were compared with a modern stand-origin map and fire-scar dates in the Kootenay Valley to determine the relative area and proximity of fires recorded as CHAR peaks. Small fires close to the lake and larger more distant fires appear as similar-sized peaks in the record. This information reinforces previous findings where CHAR peaks represent a complex spatial aggregation of local to extra-local fires around a lake site. CHAR peaks indicate frequent stand-destroying fires during the 'Mediaeval Warm Period' (-AD 1000-1300), and other significant fires at c. 1360, 1500, 1610 and 1800. We also present a proxy measure of lake-level changes based on a comparison of accumulation rates of Chara globulanis-type oospores over the last millennium and the present distribution of charophytes in the lake basin. Lower water levels, represented by few or no Chara oospores, correspond to times of regional drought and large forest fires around the lake. Higher lake levels, represented by increased Chara oospore accumulation rates, correspond to wetter climate periods during the Oort, Wolf, Sporer and Maunder solar sunspot minima, when little or no fire activity occurs around the lake.