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Humans, climate, and an ignitions-limited fire regime at Vaseux Lake Pogue, Alexandra Menke


This study investigated the role of human land use and climate as drivers of the historical fire regime of a 400ha protected area in the Okanagan region of British Columbia. I used fire scars and forest demography data to reconstruct spatiotemporal patterns in fires from 1714 - 2013. I also used paleo-climate reconstructions derived from tree ring series to evaluate whether historical fire-climate relationships changed with the displacement of indigenous peoples. Fire patterns were closely coupled with the human history of the study area. Fires were more frequent, less synchronous, and burned earlier in the season when indigenous people were stewarding the study area traditionally. Logistic regression showed that fires were also twice as likely during this period, and that topographic factors were not a significant control of the fire regime. Analysis of fire-climate relationships revealed that human land use superseded the effects of inter-annual and decadal-scale climate as a driver of historical fires. Fires occurred during a variety of conditions when indigenous people were stewarding the study area traditionally, while fires after indigenous people were displaced were associated with El Niño years, which tend to bring warm/dry conditions to the region. The historical fire regime at Vaseux was of mixed-severity in time and space, and this variability helped generate a complex forest structure. Historical fires acted to control tree establishment and mortality, and the forest is now denser than it was historically due to reduced fire frequency in the late 20th century. Continued infilling could shift the fire regime towards a greater component of high-severity fire. The results suggest that indigenous traditional land stewardship was the dominant control of historical fire dynamics at Vaseux. Managers wishing to preserve habitat and forest structures generated by the historical fire regime will need to account for the influence of indigenous burning, and modern lightning intervals will not be a sufficient baseline for setting treatment intervals. Proactive management designed to maintain a fire regime of frequent mixed-severity fires will be necessary to promote ecological resilience in an uncertain future.

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