Canadian Forest Service Publications

Long-term climate, vegetation and fire regime change in a managed municipal water supply area, British Columbia, Canada. 2019. Brown, K.J.; Hebda, N.J.R.; Schoups, G.; Conder, N.; Smith, K.A.P.; Trofymow, J.A. The Holocene 29(9):1411-1424.

Year: 2019

Available from: Northern Forestry Centre

Catalog ID: 39887

Language: English

CFS Availability: PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.1177/0959683619854523

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Mark record

Abstract

Post-glacial climate, vegetation and fire history were reconstructed from a sediment record from Begbie Lake, British Columbia, Canada, located in a municipal water supply area servicing > 350,000 people. Watershed managers have identified wildfire as a threat to water supply and seek to understand how vegetation and fire have varied through time with climate. In the cold late-glacial, open Pinus woodlands, periodically disturbed by fire, transitioned to mixed conifer forests subject to high-severity fire. The early Holocene is of interest to watershed managers because climate was warmer and drier than present. During this interval, low streamflow, abundant fire-adapted taxa, elevated background charcoal and regional increases in biomass burning indicate that fire seasons were longer and that fire was an important disturbance mechanism. Climate moistened in the mid Holocene, facilitating canopy closure and decreased fire disturbance. However, surface fires prevailed in Quercus ecosystems, which were expanding locally. Charcoal increased between 6180–2500 cal yr BP as climate further cooled and moistened, likely reflecting human activity and/or increased climate variability. Modern conditions arose within the last few millennia, impacted most recently by European settlement. In combination with paleoclimate modelling, modern management practices and forecast simulations, the Begbie Lake record informs about ecosystem changes within the watershed, yielding insights for management.

Plain Language Summary

Wildfire poses a risk in the wildland-urban interface, threatening people, property, infrastructure and natural resources. In this study, the long-term interaction between climate, vegetation and fire was investigated within the Greater Victoria Water Supply Area, which provides drinking water to >350,000 people on southern Vancouver Island, BC. Results revealed that during a past warm period, the forests around the watershed were more open relative to present day and fire-adapted species more abundant. Such conditions could recur in the future. In combination with climate modeling, modern management practices and forecast simulations, the results from this study tell us about ecosystem change within the drinking water catchment and offer management insights.