Geographical and ecological setting
The Rocky Mountain trench is the valley on the western slope of the Rocky Mountains; it runs the entire length of the Rocky Mountains in British Columbia and extends south into Montana. The southernmost portion within British Columbia has been the focus of ecosystem restoration for nearly thirty years (Daigle, 1996). Restoration in this open grassland and ponderosa pine/Douglas-fir (Pinus ponderosa/Psuedotsuga menziesii) ecosystem primarily focusses on reducing forestation of open areas and preventing catastrophic wildfires. This case study provides an overview of the Rocky Mountain Trench Ecosystem Restoration Program (RMTERP), first providing ecological and social context of restoration within the area, and then focussing specifically on the restoration of an ecosystem-maintaining fire regime.
British Columbia uses a Biogeoclimatic Ecosystem Classification (BEC) to describe ecosystems, and a corresponding Natural Disturbance Type classification to describe the typical disturbance regime of biogeoglimatic zones (Pojar, Klinka & Meidinger, 1987). While this relatively rigid way of categorizing ecosystems and disturbances leaves some "blind spots", or plain errors, which do not fit neatly into assigned classes or types (Haeussler, 2011; Kubian, 2013), they provide a useful general description of the area. Furthermore, currently they provide the basis of land management planning, including for ecosystem restoration; describing ecosystems in these terms for this case study allows comparison to other projects or land management strategies within British Columbia. It may also provide insight into challenges as climate change, or a better understanding of historical variability, shifts our perception of what constitutes typical disturbance regimes.
Biogeoclimatic zones are named after the common names of the dominant plant at the climax seral stage (BEC website). The restoration project falls within three biogeoclimatic zones: Ponderosa Pine (PP), Interior Douglas-fir (IDF) and Bunchgrass (BG). The three zones represent a gradient from the hottest and driest areas (lowest elevation, valley bottoms or south aspect), where bunchgrass dominates, towards slightly cooler and moister Douglas fir dominates areas. Presently, all of these biogeoclimatic zones contain similar species, but in different relative abundance. Tree species include ponderosa pine, Douglas-fir, and some Rocky Mountain Juniper (Juiperus scopulorum); grasses include rough fescue (Festuca campestris), Idaho fescue (Festuca idahoensis), bluebunch wheatgrass (Pseudoroegneria spicata ssp. inermis), Sandberg’s bluegrass (Poa secunda), junegrass (Koeleria macrantha), and Columbia needlegrass (Achnatherum nelsonii); forbs include Silky lupine (Lupinus sericeus), timber milk-vetch (Astragalus miser), round-leaved alumroot (Heuchera cylindrica), and meadow death-camas (Zigadenus venenosus); while shrubs are rare (Grasslands Conservation Council of British Columbia, 2004). One notable plant community assemblage is the Antelope brush (Purshia tridentata)-bluebunch wheatgrass, which is a target for restoration; invasive Kentucky bluegrass (Poa pratensis) and cheatgrass (Bromus tectorum) and native needlegrasses (Achnatherum spp.) currently exist in much of the historical range of this threatened plant community (Erickson, 2003).
All three biogeoclimatic zones fall within Natural Disturbance Class 4 (NDT4), which characterizes ecosystems with "frequent stand-maintaining fires" (Ministry of Forests, 1995). As discussed below, the frequency of fires in NDT4 ecosystems has decreased since active fire suppression began, but historically fires would have occurred in these areas as often as every 4-20 years (Daigle, 1996; Ministry of Forests, 1995). Repetitive, low-intensity fire served to maintain grasslands and open stands of mature Ponderosa Pine, both of which are otherwise encroached upon by Douglas fir (Agee, 1993; Daigle, 1996; Egan, 1998).
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