Kira Hoffman

University of Victoria
Fire suppression has altered the composition and structure of Garry oak and associated ecosystems in British Columbia, which now have some of the highest densities of Species at Risk in Canada. The absence of frequent low-severity ground fires has resulted in dense patches of non-native grasses, shrubs, and encroaching Douglas-fir trees in historic Garry oak dominated meadows. The rapid establishment and infilling of Douglas-fir trees has also affected water tables as these trees require large amounts of water for growth. The combined effect of conifer encroachment, shading, and water table draw down has decreased the spatial extent of meadow and wetland areas. This has created several management concerns in Helliwell Provincial Park located on Hornby Island, British Columbia, which has lost over 50 % of its Garry oak habitat since 1950. Higher densities of Douglas-fir and shore pine trees were found closest to the open meadow (0-15 m of transects) when compared to trees growing in the present-day forest (16-75 m of transects). These Douglas-fir trees were also significantly younger and lower densities of Garry oak trees were associated with the presence of overstory Douglas-fir trees. To slow conifer encroachment in the Garry oak meadow and restore native vegetation, we recommend that mechanical thinning of Douglas-fir be followed by a comprehensive and long-term prescribed burning program. Establishing preliminary test burns and focusing restoration efforts on the large sedge-dominated wetland will complement restoration efforts and help prepare habitat for the planned release of Taylor’s Checkerspot butterflies in Helliwell Provincial Park.

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