Effects of Deer and Elk Herbivory on Riparian Restoration in the Interior Pacific Northwest

Intensive herbivory by domestic and wild ungulates may affect riparian vegetation establishment and is of particular concern in rangeland riparian systems, where long-term herbivory can substantially reduce or eliminate deciduous, highly palatable species including aspen, willow, and cottonwood. These species are often key components of riparian ecosystems, and restoration activities focused on salmonid habitat enhancement often include planting thousands of deciduous woody seedlings in protected exclosures.  Despite recognition that ungulates can affect the success of riparian restoration, little is known about effects of wild ungulates on restoration plantings.  Here we report initial results of part of a long-term riparian restoration study within the Starkey Experimental Forest and Range in northeastern Oregon, in which we examined effects of mule deer and elk herbivory on a subset of >40,000 enhancement seedlings in the absence of cattle.  Results indicate that wild ungulate herbivory had measurable effects on seedlings. Plants protected from ungulate browsing were significantly taller than unprotected plantings, and this pattern held for six of the seven species evaluated. Moreover, seedlings exposed to browsing were less likely to survive. We discuss implications of our results for integrated ungulate management and current riparian restoration practices for salmonids in riparian ecosystems.