Restoring structure in late-successional sagebrush communities by thinning with tebuthiuron

Late successional, dense Artemisia tridentata (big sagebrush) stands restrict associated plant species production, resulting in a monotypic, shrub-dominated community that threatens biodiversity preservation and ecosystem function. Traditional practices to control A. tridentata can severely reduce or temporarily eliminate A. tridentata and other plant species. Thinning A. tridentata with low rates of the herbicide tebuthiuron enhances herbaceous plant production, community structure, ecosystem functioning, and biodiversity. Tebuthiuron was applied at rates of 0.11-1.0 kg ai/ha to A. tridentata-dominated plots at Ten Sleep (1979), Lander (1993), and Waltman (1993), Wyoming. Changes in A. tridentata canopy cover, associated plant species biomass, and community composition were evaluated 13 and 14 years post-treatment at Ten Sleep, and 2 and 4 years post-treatment at Lander and Waltman. At all sites A. tridentata canopy cover decreased proportionally with increased tebuthiuron rate. Biomass of grasses increased as shrub biomass and cover decreased with increasing tebuthiuron rate. Forb biomass varied between treatments across sample year and site. Shifts from shrub-dominated control to grass-dominated treatment plots were attributable to biomass differences of A. tridentata and 2-3 grass species among treatments. The number of plant species was not significantly different between treatments at any site. Similarity indexes revealed progressively greater dissimilar plant composition between the control and sequential treatment plots of increased tebuthiuron rate. Incremental rates of tebuthiuron produce gradual changes in plant species composition without reducing species richness, which may have utility in certain restoration projects.