Volume 25, 12

Tropical Grasslands (1991) Volume 25, 12–19

Effect of grazing on native gramineae in Concepción, Santa Cruz, Bolivia

T.J. KILLEEN

Department of Botany, Iowa State University, Ames, Iowa, USA

Abstract

The effect of intensive grazing on 57 species of Gramineae was studied in 4 vegetation types (cerrado, seasonally inundated savanna, valleyside campo, and semideciduous forest) near Concepción, Santa Cruz, Bolivia. The relative abundance of each species was estimated from paired stands (relevés) along fence rows dividing grazed and ungrazed ranches. Thirteen species were significantly less abundant and 4 species were more abundant in grazed stands when compared to ungrazed stands. In cerrado, the total number of species in grazed stands was significantly reduced and the unpalatable grass, Elionurus muticus, was the dominant species in both grazed and ungrazed stands. The relatively palatable grasses, Thrasya petrosa, Schizachyrium microstachyum, and Schizachyrium sanguineum were important constituent species of cerrado and were the most negatively affected by selective grazing. Savanna wetland and semideciduous forest communities lack a single dominant grass species and differences in species richness were not significant between grazed and ungrazed stands.