Rangeland Ecology & Management

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Gunnell, Kevin L.
Monaco, Thomas A.
Summers, Danny
Society for Range Management
Publication Year

The encroachment of pinyon (Pinus spp.) and juniper (Juniperus spp.), i.e. P-J, into sagebrush (Artemisia spp.) rangelands in the Intermountain West is well documented. Encroachment has negative impacts on sagebrush communities, threatens wildlife habitat, and diminishes watershed functioning. The Utah Watershed Restoration Initiative (UWRI) was enacted in 2004 to mitigate the impacts of P-J encroachment throughout the state of Utah through interagency cooperation to implement large-scale mechanical vegetation manipulations. Using data collected by the Utah Division of Wildlife Resources (UDWR) Range Trend Project from 68 UWRI projects located on 32 different ecological sites throughout the state, we used meta-analysis to assess the efficacy of three common P-J removal methods (tree mastication, chaining, and ‘lop-and-scatter') over nine years. With the exception of chaining, all treatments increased total shrub and sagebrush cover. Perennial grass and forb cover also increased, but this response varied by treatment and post-treatment timeframe. While perennial grass cover was significantly more abundant in the chaining and lop-and-scatter treatment, only perennial forb cover was more abundant in the mastication treatment. Without exception, all treatments led to significantly lower bare ground and greater soil surface litter cover. We relate these differences among treatments to the severity of pre-treatment P-J encroachment, differing ground cover disturbance, and supplemental seeding. We also assessed plant community composition changes over time with indicator species analysis. In general, exotic forbs were significant indicator species in the first three years after mastication and lop-and scatter treatments, yet native forbs and shrubs were indicators after six and nine years, respectively. In contrast, seeded grasses, forbs, and shrubs were significant indicators in post-chaining communities. We conclude that although P-J reduction has greatly augmented herbaceous and shrub vegetation, additional analyses based on ecological sites are needed to evaluate how vegetation structure stabilizes into alternative stable states in response to treatments. 

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Conference Proceedings
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SRM Sacramento, CA