Lifeboat or sinking ship: will the size and shape of Old-Growth Management Areas provide viable future habitat for temperate rainforest lichens?

Abstract

The Kispiox Timber Supply Area, a 1.3 million ha region in northwestern British Columbia, Canada, supports a significant assemblage of temperate rainforest (oceanic) lichens that depend on old forests. Given their known sensitivity to edge effects, we ask whether or not the current configuration of Kispiox Old-Growth Management Area (OGMA) reserves will provide viable future habitat for oceanic lichens as surrounding landscapes are progressively logged in coming decades. Landscape indicators were calculated from provincial map data sets. Old Interior Cedar–Hemlock biogeoclimatic zone forests, the primary habitat for Kispiox oceanic lichens, had a landscape shape index of 6.4 in OGMAs, indicative of elongate shapes susceptible to edge effects. Mean patch size in OGMAs was 43 ha, with the largest patch size being 1 378 ha. In contrast, the landscape shape index for pre-industrial old cedar–hemlock forests was 1.3, with a mean patch size of 1 293 ha and largest patch size of 23 357 ha. When modelled edge effects were extended to 120 m, only 25% of cedar–hemlock forests in Kispiox OGMAs remained interior habitat (7 754 ha total). Adoption of silvicultural practices that maintain buffer zones around existing OGMAs, and the designation of additional OGMAs, especially in watersheds with intact old cedar–hemlock forests, is recommended to conserve oceanic lichen communities in the Kispiox region.