Spread of Introduced Lehmann Lovegrass Along a Grazing Intensity Gradient

Abstract

1. Changes in density of Lehmann lovegrass and native grasses, and the proportion of lovegrass present along a livestock grazing intensity gradient were measured on six occasions in permanent plots during 1972-90, on the Santa Rita Experimental Range, Arizona, USA. The gradient included grazing exclosures and plots radiating away from a cattle watering point. Lehmann lovegrass spread from sowings done during 1945-59 4km from the water point and an average 1 8 km from the exclosures. 2. Lovegrass density increased with time but was not affected by different grazing intensities. Native grass density decreased, and lovegrass relative abundance increased with time and as grazing intensity increased. Lovegrass density and relative abundance did not differ between adjacent ungrazed and grazed areas. 3. Livestock grazing was not necessary for Lehmann lovegrass to spread, but the lovegrass relative abundance was greater at higher grazing intensities.