The natural disturbance regime most commonly associated with boreal and sub-boreal forests in BC is one of reoccurring fires that create a mosaic of different seral stages on the landscape. Forest harvesting, similarly, creates a mosaic of different aged forests within managed landscapes, though often at different spatial scales from that of fire. Recently, there has been a greater recognition of the role of old-forest attributes within northern forested ecosystems, and recognition that some old-forest features may be spatially constrained within these landscapes, for instance, associated with topographic influences that constrain fire spread. One of these features is that of deciduous wetland swales (DWS), upland seepage areas and wetlands dominated by willow and alder communities. Whereas swales associated with wetlands often receive protection due to riparian reserves or lack of commercial timber in close proximity, upland DWS are often in the midst of commercial forest and thus have commonly been included as part of the net area to be reforested (i.e., conversion to forest). Thus herbicide or mechanical treatments have often been prescribed to reduce the aerial extent of upland willows and alder swales.
There has been an emerging literature describing these swales as key habitats that play a major role in supporting regional flora and fauna (DeLong and Sanborn 2000). Recent surveys by the BC Ministry of Forests (DeLong pers. com.) indicate that relatively few upland DWS communities have been retained in managed forests within the Prince George Forest District. With recognition of their importance in regional landscapes there is now a pressing need for information that would support forest licensees in developing prescriptions to maintain these attributes in regional landscapes and to characterize key biodiversity indicators associated with DWS habitats.
The proposed research would address this information gap on DWS in central interior BC using a two-pronged approach. 1) We would characterize the aerial extent of and topographic features associated with DWS occurrence. This study component would combine queries to the Vegetation Resource Inventory with air photo-interpretation and ground truthing to characterize stand structural characteristics such as DWS age, canopy cover, and canopy structural features. 2) We would examine DWS as conservation refugia for arboreal lichens, examining both forage lichens that support ungulate habitat values and cyanolichens that support site productivity. Lichens have widely been used as indicators of site continuity and old-forest values, most recently in studies on wet-belt forests of the northern Caribou Mountains and Rocky Mountain trench (Radies and Coxson 2003). Forage lichens would be assessed using estimates of lichen community composition in DWS habitats, while cyanolichen contributions to site productivity would be assessed by acetylene reduction (nitrogen fixation) assays.
We would propose conducting these studies along a north-south regional gradient in central interior BC, looking at montane forests within the wet cool and very wet cool subzones of the Sub-boreal Spruce Zone in both the Mackenzie and Prince George Forest Districts. This research will provide an evaluation of whether or not current assumptions about DWS habitats are providing effective conservation biology protection for this landscape level attribute.
Although the immediate focus of the proposed project will use lichens as indicators of key refugia values, our characterization of the aerial extent and distribution of DWS sites will provide important contributing information to the management of wildlife habitat values; both for woodland caribou, which have been shown to browse on arboreal lichens in DWS sites (typically in conjunction with early winter foraging on terrestrial lichens in adjacent upland sites; Parker pers. com.), and for grizzly bear, which use DWS for feeding and bedding (Dale Siep ...