Spread of introduced Lehmann lovegrass along a grazing intensity gradient.
Changes in density of sown E. lehmanniana and native grasses (dominated by Digitaria californica, Bouteloua curtipendula, B. eriopoda, Muhlenbergia porteri and Aristida spp.) and proportion of E. lehmanniana present along a livestock grazing intensity gradient were measured on 6 occasions in permanent plots during 1972-90 on the Santa Rita Experimental Range, Arizona. The gradient included grazing exclosures and plots radiating away from a cattle watering point. E. lehmanniana spread from sowings made in 1945-59 4 km from the water point and an average 1.8 km from the exclosures. E. lehmanniana density along the gradient increased with time but was not affected by different grazing intensities. Native grass density decreased and E. lehmanniana relative abundance increased with time and as grazing intensity increased. E. lehmanniana density and relative abundance did not differ between adjacent ungrazed and grazed areas. It was concluded that livestock grazing was not necessary for E. lehmanniana to spread, but that its relative abundance was greater at higher grazing intensities.