Holocene disturbance dynamics from a pine-dominated forest in central British Columbia, Canada

A lake sediment record was retrieved from the Sub-Boreal Pine-Spruce biogeoclimatic zone on the Chilcotin Plateau in central British Columbia, Canada. The record is being analyzed for charcoal, pollen, and magnetic susceptibility, as well as insect and mollusc content. The oldest radiocarbon age is 9.2 cal BP, illustrating that the record spans most of the Holocene. Regarding fire disturbance, charcoal fragments are persistent throughout the core, revealing that fire disturbance has characterized the site for millennia. In total, 74 fire events were recognized. During the warm dry early Holocene, fire frequency was 12-15 fires 2000 yr-1 and peak magnitudes were low, possibly in response to a more open landscape. A change in fire regime occurred at ca. 5000 cal BP, as fire frequency increased, peaking at ca. 20 fires 2000 yr-1 by 3000 cal BP. Peak magnitude likewise increased notably, possibly in response to the development of denser forest cover. On-going analysis of pollen will better constrain the vegetation history in this poorly sampled region. In contrast to charcoal, which was pervasive, Dendroctonus ponderosae (mountain pine beetle) remains were absent in both modern and paleo samples. Given that several insect outbreaks have occurred in the region in the last 100 years, the scarcity of remains is likely related to taphonomic issues.