The effects of drought on plant response in Northern Chehuahuan Desert rangelands

Abstract

Short term grazing trials were started in June 1992 and continued until 2000; The pastures were grazed in June and September each year except 1996, 1999 and 2000 because of drought. The trials were conducted at New Mexico State University’s Chihuahuan Desert Rangeland Research Center 38 km north of Las Cruces, New Mexico. Short-term grazing trials with 3 to 6 cows lasting 3 to 6 days were conducted in June and September. The treatments were no-grazing (control), moderate and heavy grazing. The before and after grazing perennial grass biomass production was used to determine the grazing use levels in each pasture. Plant attributes measured were cover, density and herbage production. The objectives of the study were to (1) determine the impact of drought on herbage production and vegetation compositional changes and (2) determine the effect of soil texture and depth on response of plants under drought conditions. Drought affected vegetation the same under the different grazing treatments and within seasons (P > 0.05). It was also observed that herbage production and basal cover were highly correlated with previous 12 months precipitation for both grazing treatments and within seasons. Total grass biomass was correlated with precipitation at (r = 0.75, 0.74, 0.65) for June season and (r - 0.67, 0.71, 0.60) for September season under the control, moderate and heavy grazing, respectively. Total plant cover was also highly correlated with precipitation (r = 0.81, 0.80, 0.83) for June season and (r = 0.75, 0.85, 0.87) for September season under the above 3 grazing levels, respectively. Basal cover for perennial grasses, perennial forbs and shrubs were generally highly correlated with precipitation as opposed to annual forbs and grasses. No distinct patterns were found between soil depth and perennial grass cover for the years tested (1992, 1994, 1997 and 2000). Vegetation diversity did not differ between the different treatments and within seasons (P > 0.05).