The impact of juniper removal on shrubs and understory vegetation and its implications for sagebrush dependent vertebrate herbivores

The expansion of trees into previously grass- and shrub- dominated ecosystems is a global phenomenon threatening ecosystem integrity and function in encroached systems, including the North American sagebrush biome. This ecosystem is currently in peril, threatened in part by juniper (Juniperus sp.) encroachment. Sagebrush (Artemisia sp.) ecosystems contain a diversity of forage, including grasses, forbs, and shrubs, that serve as a key food source for vertebrate herbivores. Removal of encroached juniper has been used by land managers as a widespread restoration technique in sagebrush ecosystems, however, the long-term impact of this restoration action on shrubs and understory vegetation has not been thoroughly examined in the context of sagebrush dependent vertebrate herbivores. In 2020 and 2021, we studied shrub and understory vegetation response to juniper treatment in the sagebrush of northern Nevada and northeastern California. Juniper treatments completed between 2008 and 2020 were surveyed and sampled to assess the impact of this restoration action on grasses, forbs, and shrubs over time. Forage biomass was higher in old treatments than untreated reference sites, which was a trend that persisted across all vegetation functional groups. Differences in plant cover were slight or had inconsistent nonlinear trends between reference sites and treatments. Forage from treated sites had higher crude protein levels than forage from untreated sites, although the nutritional difference was slight. Our results suggest that juniper treatments that increase forage quantity and improve forage quality may benefit sagebrush dependent wildlife or domestic livestock in conifer-encroached ecosystems.