Drought and grazing influence on northern Chihuahuan desert rangelands, New Mexico

Abstract

A short term cattle grazing trial was started in June 1992 in the Chihuahuan Desert in Southern New Mexico to study the influence of drought and grazing on plant responses. Paddocks were grazed in June and September each year except in 1996, 1999 and 2000 because of drought. Summer growing season precipitation was below average 6 of the 9 years of the study. Only 29 mm fell from July through September in 2000, the driest summer. Most herbaceous perennial plants died during the study. Perennial grass basal cover declined from a high near 1.6% in 1992 to 0.4% in 2000. Densities of perennial grasses and forbs decreased from near 50 plants m*2 In 1992 to fewer than 15 plants m2 by 2000. Annual forbs and grasses germinated and grew in response to specific rainfall events regardless of drought conditions. No significant (P> 0.10) year grazing treatment interaction was found for basal cover and density of plants. However, both attributes were significant (P< 0.10) across years. Correlations between grazing treatments and precipitation for plant total cover were significant (P < 0.10) and ranged between 0.75 and 0.87. Loss of plant density and basal cover occurred on both grazed and non-grazed areas during the study, indicating that drought was primarily responsible for any plant changes while grazing effects at the intensities studied were minimal.