Productivity of Long-Term Grazing Treatments in Response to Seasonal Precipitation

Abstract

Estimates of forage production for long-term ungrazed, lightly, moderately, and heavily grazed treatments (0,20,40,60% removal of annual forage production) established in 1939 in shortgrass steppe communities were subjected to multiple regression analyses to assess long-term temporal trends resulting from grazing and short-term sensitivities to abiotic factors. Average production based upon alI data from 1939-1990 was 75,71,68, and 57 g mm2yrm1 for ungrazed, lightly, moderately, and heavily grazed treatments, respectively. Variability in forage production was explained mostly by cool-season precipitation, and magnitude of forage production was more sensitive to annual fluctuations in precipitation than to long-term grazing treatments. Production per unit increase of precipitation was greater for cool-season than warm-season precipitation, but only when cool-season precipitation was above average. This was attributed to differences in evaporative demand of the atmosphere resulting in different utilization-efficiencies of small and large rainfall events in the 2 seasons. Based upon a regression model constructed using data from 1939 through 1962, forage production was not effected by grazing to 20 to 35% removal. For pastures of average relative productivity, grazing at 60% level of consumption for 25 years resulted in a 3% decrease in forage production in wet years and a 12% decrease in dry years. Estimates of productivity after 50 years of heavy compared to light grazing treatment were -5 and -18% for wet and average years of precipitation, respectively.

Stocking rate, precipitation, and herbage production on sand sagebrush-grassland

“…On the other hand, sand dropseed and blue grama were not responsive to precipitation and, as a result, their relative contribution to total production declined during a period of increased precipitation. Milchunas et al (1994) hypothesized that long -term heavy grazing might reduce the ability of a grassland to increase production in years of favorable precipitation. However, when testing this hypothesis in shortgrass steppe Milchunas et al (1994) found that heavy grazing did not reduce production potential in years with high precipitation.…”

“…Milchunas et al (1994) hypothesized that long -term heavy grazing might reduce the ability of a grassland to increase production in years of favorable precipitation. However, when testing this hypothesis in shortgrass steppe Milchunas et al (1994) found that heavy grazing did not reduce production potential in years with high precipitation. Our results also reject this hypothesis since herbaceous production responded to favorable precipitation equally well at all stocking rates throughout the measurement period.…”

Long Term Effect of Major Disturbances on the Northern Mixed Grassland Ecosystem—A Review

“…[35]). Meanwhile Milchunas [36] found that production was highest in ungrazed treatments, and decreased as grazing intensity increased in short-grass prairie.…”

Investigating vegetation biophysical and spectral parameters for detecting light to moderate grazing effects: a case study in mixed grass prairie

“…Patton et al [13] indicated that moderate grazing in a Kentucky bluegrass-dominated rangeland can maintain a higher level of herbage production as compared to complete rest or overgrazing, while Belsky [14] and Painter and Belsky [15] reported no evidence that herbivory benefits grazed plants. Milchunas et al [16] found that production was highest in ungrazed treatments, and decreased with increased grazing intensity in short-grass prairie.…”