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EFFECTS OF INTENSE, SHORT-DURATION GRAZING ON MICROTOPOGRAPHY IN A CHIHUAHUAN DESERT GRASSLAND
Citation:
Nash, M S., E. Jackson, AND W. G. Whitford. EFFECTS OF INTENSE, SHORT-DURATION GRAZING ON MICROTOPOGRAPHY IN A CHIHUAHUAN DESERT GRASSLAND. Presented at Ecological Society Meeting, Tucson, AZ, August 4-9, 2002.
Impact/Purpose:
The primary objectives of this research are to:
Develop methodologies so that landscape indicator values generated from different sensors on different dates (but in the same areas) are comparable; differences in metric values result from landscape changes and not differences in the sensors;
Quantify relationships between landscape metrics generated from wall-to-wall spatial data and (1) specific parameters related to water resource conditions in different environmental settings across the US, including but not limited to nutrients, sediment, and benthic communities, and (2) multi-species habitat suitability;
Develop and validate multivariate models based on quantification studies;
Develop GIS/model assessment protocols and tools to characterize risk of nutrient and sediment TMDL exceedence;
Complete an initial draft (potentially web based) of a national landscape condition assessment.
This research directly supports long-term goals established in ORDs multiyear plans related to GPRA Goal 2 (Water) and GPRA Goal 4 (Healthy Communities and Ecosystems), although funding for this task comes from Goal 4. Relative to the GRPA Goal 2 multiyear plan, this research is intended to "provide tools to assess and diagnose impairment in aquatic systems and the sources of associated stressors." Relative to the Goal 4 Multiyear Plan this research is intended to (1) provide states and tribes with an ability to assess the condition of waterbodies in a scientifically defensible and representative way, while allowing for aggregation and assessment of trends at multiple scales, (2) assist Federal, State and Local managers in diagnosing the probable cause and forecasting future conditions in a scientifically defensible manner to protect and restore ecosystems, and (3) provide Federal, State and Local managers with a scientifically defensible way to assess current and future ecological conditions, and probable causes of impairments, and a way to evaluate alternative future management scenarios.
Description:
We measured the effects of short-term intense grazing by domestic cattle on the microtopography of a black-grama grass (Bouteloua eriopoda) dominated desert grassland. Plots were grazed during winter or summer for 24-36 hours by 20-40 yearlings in 1995 and 1996. Soil microtopography was measured with an erosion bridge by measuring pin lengths above the leveled bridge. Short-duration intense grazing resulted in significant loss of microtopographic relief There were significant reductions in the numbers of mounds and depressions in grazed plots compared with ungrazed plots. Average mound height was significantly lower in grazed plots than in ungrazed plots, and average depth of depressions was significantly reduced in grazed plots. The reduced microtopography resulting from short-duration, intense grazing affects water storage patterns and soil nutrient patterns.