Author
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Gillen, Robert |
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Sims, Phillip |
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Submitted to: Journal of Range Management
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/18/2003 Publication Date: 3/1/2004 Citation: GILLEN, R.L., SIMS, P.L. STOCKING RATE, PRECIPITATION, AND HERBAGE PRODUCTION ON SAND SAGEBRUSH-GRASSLAND. JOURNAL OF RANGE MANAGEMENT. 2004. v. 57(2). p. 148-152. Interpretive Summary: Knowledge about the relationship between grazing intensity and plant production is fundamental to the sustainable management of rangelands. Two general management principles currently in use state that forage production declines as grazing intensity increases and production from weeds increases as grazing intensity increases. Our objective was to determine the impact of grazing intensity on plant production from Southern Plains rangelands. Light, moderate, and heavy grazing intensities were applied from 1941 to 1961. Plant production was measured from 1958 to 1961, the last 4 years of the grazing study. Total forage production averaged over all treatments and years averaged about 0.7 tons per acre. Grasses contributed 89% of the total while broad-leaved plants (or weeds) contributed 11%. Total forage production did not differ between light, moderate, and heavy grazing intensities. There were no differences among grazing intensities for production of any individual grass species. Production of broad-leaved plants was also not affected by grazing intensity. Differences in production due to weather fluctuations among years were much greater than differences among grazing intensities for all vegetation components. Overall, forage production of this native sagebrush-grassland was little affected by 20 years of differential stocking rates. The general management principles of decreased forage production and increased weed production as grazing intensity increases did not hold under the conditions of this study. Results from companion studies indicate that ranchers should be able to graze at a level that maximizes net profit and still maintain the ecological integrity of these native grasslands Technical Abstract: Knowledge of the relationship between stocking rate or grazing intensity and plant production is fundamental to the sustainable management of rangelands. The general management paradigm is that plant production declines as stocking rate increases. Our objective was to determine the impact of stocking rate on herbaceous production of a sand sagebrush (Artemisia filifolia Torr.)-grassland. Light, moderate, and heavy stocking rates averaging 43, 57, and 85 animal-unit-days/ha (AUD/ha) for year-round grazing were applied from 1941 to 1961. Herbaceous plant production was determined by sampling standing crop in temporary exclosures at the end of the growing season from 1958 to 1961, the last 4 years of the grazing study. Total herbaceous production averaged over stocking rates and years was 1490 kg/ha. Grasses contributed 89% of the total while forbs contributed 11%. Total production averaged 1540, 1470, and 1450 kg/ha for light, moderate and heavy stocking rates, respectively. There were no significant differences among stocking rates for total production or for the production of any individual grass species (P>0.05). Forb production was also not affected by stocking rate, averaging 200, 140, and 120 kg/ha for light, moderate, and heavy stocking (P>0.05). Differences in production among years were much greater than differences among stocking rates for all vegetation components. Little bluestem [Schizachyrium scoparium (Michx.)Nash] and sand lovegrass [Eragrostis trichodes (Nutt.) Wood] showed the greatest responses to favorable precipitation. Herbaceous production of this sand sagebrush-grassland was little affected by 20 years of differential stocking rates. The management paradigm of general increases in forbs across the landscape as stocking rates increase should be reconsidered |
