Herbivory by domestic and wild ungulates exerts a strong influence on the composition and structure of plant communities. However, little is known regarding vegetation responses to different levels of ungulate browsing pressure. These effects are of particular interest in forest rangelands of western North America, where intensive herbivory by native and domestic ungulates has the potential to substantially reduce or eliminate deciduous, highly palatable species such as cottonwood (Populus trichocarpa), and willow (Salix spp.). Potential interactions of ungulate herbivory with episodic disturbances of silviculture, fire, and other land uses are not well documented, but are thought to operate synergistically to affect forest dynamics. We assessed the effect of variable browsing pressure by cattle and elk on shrubs in fuels treated (mechanical removal of fuels followed by prescribed burning) and non- fuels treated coniferous forest rangelands in the interior Pacific Norwest. Seven treatment paddocks (three with cattle exclusion and low, moderate and high elk browsing pressure, three with elk exclusion and low, moderate and high cattle browsing pressure, and one with both cattle and elk exclusion) were established at six sites, and individual shrub recruitment, growth, height and survival were monitored for six years. Results indicated that densities of deciduous species were >4 times higher in response to fuels reduction treatments (84 individuals/ha) compared to areas of no treatment (19 individuals/ha). Effects of browsing by cattle and elk on shrub height volume, growth, and survival were similar. However, elk, regardless of stocking density, browsed a significantly greater proportion of Populus and Salix individuals than cattle. Even at low stocking rates, elk browsed the vast majority of highly palatable shrub species particularly in fuels-treated stands. Effects on size, height, and survival will be presented. Results provide insight into factors influencing the abundance of these shrub species in forest rangelands and have implications for forest and ungulate management.
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