Submitted to: Society for Range Management, New Mexico Section Meeting
Publication Type: Abstract only
Publication Acceptance Date: 1/8/2002
Publication Date: 1/8/2002
Citation: DREWA, P.B., PETERS, D.C., HAVSTAD, K.M. EFFECTS OF FIRE AND GRAZING ON VEGETATION IN NORTHERN CHIHUAHUAN DESERT GRASSLANDS. SOCIETY FOR RANGE MANAGEMENT, NEW MEXICO SECTION WINTER MEETING. 2002. ABSTRACT P. 5. Interpretive Summary:
Technical Abstract: We examined experimentally the effects of growing-season fires and livestock grazing on plant community structure in Chihuahuan Desert grasslands of southern New Mexico. Four 200m x 200m plots were established in each of four different blocks. Treatments were either applied or not applied, resulting in four treatment combinations that were each assigned randomly to one of the four plots within each block. Fires were prescribed in June 1999. Beginning in September 1999, unfenced plots were exposed to 12 months of continuous livestock grazing where utilization was <40%. Plant cover and frequency were measured immediately before and after treatments using a vertical line point intercept method every 10cm along five 150m-transects within each plot. Cover of Bouteloua eriopoda, the dominant perennial grass, decreased only by 1.22% following burning but increased 2.20% in fire-excluded areas. Its frequency decreased 6.49% and 0.48% in burned and unburned plots, respectively. After fires, collective perennial forb cover and frequency increased 1.46% and 3.81%, respectively, but decreased as much as 4.04% in unburned plots. Cover and frequency of annuals also increased up to 7.25% and 20.63%, respectively, in burned plots but increased as little as 0.3% in fire-excluded areas. Livestock grazing had a similar effect as fire on only cover of B. eriopoda. Contrary to past research, fire did not result in delayed recovery of B. eriopoda. Additionally, greater increases in cover and frequency of perennial forbs and annuals after burning enhanced overall grassland diversity. Rapid vegetation responses following fire may have been influenced by patterns of precipitation that were equivalent to the average, especially in the immediate post-fire environment.