Assessment of Ungulate Resource Values Within the Cline River Subbasin Following the 2009 Upper North Saskatchewan River Prescribed Fire
R. Anderson, E. Anderson, and C. Rasmussen
In response to the effects of wildfire control and the consequences of a lack of natural fire events on the landscape, Alberta Conservation Association partnered with other agencies to help plan a prescribed fire and monitor ungulate resource values within the Cline River subbasin southwest of the town of Rocky Mountain House, Alberta. The Upper North Saskatchewan River prescribed fire, conducted in 2009, was intended to restore ungulate winter range value within a landscape that had aged beyond the natural range of variability. The Cline River Subbasin Ungulate Winter Range Restoration Plan outlined values, objectives, indicators, and targets to evaluate ungulate resource values before and after a series of treatments. This report outlines the monitoring program conducted between 2005 and 2015, as well as an initial evaluation of treatment success on landscape-, ecosystem-, and species-level objectives and indicators for ungulates.
Outcomes at the landscape- and ecosystem-level (presented in the appendices) generally indicated achievement of, or substantial progress towards, winter range targets; however, outcomes at the species-level were more mixed and perhaps less beneficial for winter range than predicted. Stand-age distribution and disturbance rates within ungulate winter range of the Cline River subbasin shifted towards targets, recognizing these long-term values may require multiple treatments to achieve. The Upper North Saskatchewan River prescribed fire mimicked historical large fires in its total burned area and number and size of remnant unburned patches, but had more burned patches than historical wildfires.
At the species-level, forage access for bighorn sheep should improve as the prescribed fire occurred primarily on southern exposures used by sheep in the winter and the increased horizontal visibility should assist in predator detection. Similarly, open forage areas were increased in proximity to security cover, which should increase forage access for mule deer and elk. Forage abundance showed an immediate short-term increase in grass and herbaceous forb biomass but had decreased by six years post-fire, while grass and forb cover reached peak values at six years post-fire. These results were noted primarily in montane study areas and were less consistent in subalpine study areas. Shrub biomass showed a slight decrease but by six years post-fire, shrub cover had increased. Finally, forage quality for elk as measured through a Forage Preference Index showed the most unanticipated result; spring indices increased at most study areas while there was no change in winter forage preference indices. Recent studies have indicated the importance of quality late spring and especially summer
nutritional resources for many aspects of elk reproduction. We recommend that future range restoration work for elk should thus focus not on winter range but on other seasons instead.