Canadian Forest Service Publications
Herbicide-induced changes to ungulate forage habitat in western Alberta, Canada. 2006. Strong, W.L.; Gates, C.C. Forest Ecology and Management 222(1): 469-475.
Available from: Northern Forestry Centre
Catalog ID: 25987
The effects of herbicide (hexazinone) treatments on ungulate forage were evaluated in a hardwood forest clearcut. Species composition data were collected in three replicate 0-, 2-, and 4-kg/ha (active ingredient) plots, prior to treatment (Year 3 after clearcutting), then in Years 5, 9, and 20. Forage index values were calculated based on shrub densities (winter) and canopy plant cover (summer) weighted according to forage preference ratings for elk (Cervus elaphus), moose (Alces alces), and mule deer (Odocioleus hemionus). Five years after clearcutting, the 0-kg plots had maximum winter values 3.6–5.5 times greater than unharvested vegetation, and then declined; but the 2- and 4-kg herbicide-treated plots had values that were up to 18 and 48% below 0-kg herbicide levels, respectively. Herbicide treatment reduced winter ungulate and summer elk forage values throughout the duration of the study. Aspen (Populus tremuloides) and saskatoon (Amelanchier alnifolia) were the most abundant species and the most affected by hexazinone. In contrast, herbicide application enhanced summer forage for moose about 14%. Cumulative effects models based on a 20-year scenario suggested hexazinone treatment of clearcut vegetation reduced winter ungulate (<_ 20%) and summer elk (~6.5%) forage availability relative to the untreated condition. Moose summer values increased slightly, whereas mule deer forage was unaffected.