Evaluation of techniques to protect aspen suckers from ungulate browsing in the Black Hills

Excessive browsing by cattle (Bos taurus L.) and wild ungulates, particularly elk (Cervus elaphus L.), sometimes inhibits growth and maturity of quaking aspen (Populus tremuloides Michx.) suckers in Western North America. In areas where aspen stands are in poor condition or declining, protecting suckers from ungulates may be necessary. This study compared the utility of livestock fences, complete wildlife exclosures, barriers created from slash debris, and tree hinging during 2004 and 2005 in the Black Hills of South Dakota. All of the barriers significantly reduced percentage browsing of aspen suckers compared with the pretreatment average (78%) and posttreatment control (79%). Slash treatments and livestock fences decreased ungulate browsing by 19%, hinge treatments decreased it by 39%, and wildlife fences eliminated nearly all incidences of sucker browsing. The average length removed per terminal stem for aspen suckers decreased from 20.8 to 14.4 cm across all treatments. After 1 year, the mean number of suckers above 100 cm height in both the hinge and slash treatments were significantly greater than both the fence treatments and control. Data showed that autumn and winter browsing was primarily by wild ungulates. Slash barriers can replace livestock fences where cattle affect aspen suckers. Hinge barriers are more useful than both slash barriers and livestock fences in areas where wild ungulates are the primary browsers.