Responses of the Shrub, Baccharis pteronioides, to Livestock Exclosure in Southeastern Arizona

Abstract
This research focused on the behavior of populations of the shrub, Baccharis pteronioides D.C. (Asteraceae: Astereae), that were protected from browsing by domestic cattle. Livestock were removed from the Research Ranch (3160 ha) in 1968. Data on plant density, fire resistance and browsing pressure were collected in 1982 and 1983 from paired plots on the exclosure and neighboring cattle ranches. Protected populations of Baccharis were denser than those on the adjacent cattle ranches, and were comparable to densities of the shrub found on nearby small livestock exclosures established in 1925 and 1949. The protected populations appear stable and are not likely to decrease in the near future. Baccharis pteronioides is also fire-resistant. These findings suggest that semidesert grassland in this area will not return to its earlier shrub-free state in the foreseeable future.