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

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. Stocking rates averaging 43, 57, and 85 animal-unit-days ha-1 (AUD ha-1) 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 1,490 kg ha-1. Grasses contributed 89% of the total while forbs contributed 11%. Total production averaged 1,540, 1,470, and 1,450 kg ha-1 for stocking rates of 43, 57, and 85 AUD ha-1 y-1, respectively. There were no 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-1 for stocking rates of 43, 57, and 85 AUD ha-1 y-1 (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.