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ARS Home » Plains Area » Las Cruces, New Mexico » Range Management Research » Research » Publications at this Location » Publication #163153
Title: EFFECTS OF INTENSE, SHORT-DURATION GRAZING ON MICROTOPOGRAPHY IN A CHIHUAHUAN DESERT GRASSLAND

Author
item NASH, MALIHA - US-EPA
item JACKSON, ERIK - DESERT RESEARCH INSTITUTE
item WHITFORD, WALTER - NMSU COLLABORATOR

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2003
Publication Date: 2/1/2004
Citation: NASH, M.S., JACKSON, E., WHITFORD, W.G. EFFECTS OF INTENSE, SHORT-DURATION GRAZING ON MICROTOPOGRAPHY IN A CHIHUAHUAN DESERT GRASSLAND. JOURNAL OF ARID ENVIRONMENTS. 2004. V. 56(3). P. 383-393

Interpretive Summary: We compared the effects of 3 consecutive years of intensive grazing at a rate of less than 48 hours per year by 20 to 40 yearling cows per hectare on soil surface microtopography on nine grazed, 0.5-hectare plots and nine ungrazed, 0.5-hectare, control plots. Chihuahuan Desert black grama grasslands are characterized by low mounds on which grass tussocks reside and bare patch depressions between the tussock mounds. Three short-duration, intense grazing sessions resulted in significant reduction in height of micromounds and depth of the intermound depressions. There were no differences in the effect of grazing on microtopography on plots where mesquite shrubs had been removed and on plots where mesquite shrubs were left intact. Also, there were no significant differences in the season of grazing (winter vs. summer). Intense grazing on the sandy soils of Chihuahuan Desert black grama grasslands destroys the microtopographic relief that is important to the structural integrity of the grasslands. Loss of microtopography reduces surface roughness and increases the probability of soil loss by wind erosion. Loss of microtopography by intense, short-duration grazing is therefore an initial step in the degradation of black grama grasslands.

Technical Abstract: We studied the effect of three consecutive years of short duration (<48 h per year), and intense grazing (20'40 yearling cows per hectare) on soil surface microtopography in a Chihuhuan Desert grassland. We also studied the effects of shrub removal plus grazing on microtopography. Microtopography was measured in 18 plots (treatments). Treatments were a combination of two factors: (1) three levels of grazing (winter-grazed, summer-grazed, and not grazed), and (2) two levels of habitat structure (shrubs-removed and shrubs-intact). Mesquite (Prosopis glandulosa) shrubs were removed from half of the plots (nine out of 18 plots). The average height of the micromounds, the average depths of intermound depressions, and the number of micromounds were significantly reduced on the grazed plots. Shrub removal had no significant effect on the height of the micromounds or the depth of the intermound depressions of ungrazed plots. There were significant differences in average micromound heights and intermound microdepression depths attributable to the season of grazing. Microtopography was significantly reduced on grazed plots from which shrubs were removed, compared to ungrazed plots, and grazed plots with shrubs present. Grass canopy reduction, and destruction of the micromound structure in a short duration, plus intense grazing results in erosion of micromounds and in-filling of intermound depressions. The loss of microtopography coupled with reduction in vegetation height and cover resulting from short-duration intense grazing by cattle exposed soils to an increased risk of soil erosion Destruction of the micromound/microdepression topography by cattle changes the spatial patterns of water infiltration, and may homogenize nutrients in desert grasslands.