| K.M. Olson-Rutz, C.B. Marlow, K. Hansen, L.C. Gagnon and R.J. Rossi |
| Authors are former research associate, Animal and Range Sciences Department, Montana State University, Bozeman, MT, 59717; associate professor, Animal and Range Sciences Department, Montana State University, Bozeman, MT, 59717; associate professor, Earth Sciences Department, Montana State University, Bozeman, MT, 59717; associate professor, Animal and Range Sciences Department, Montana State University, Bozeman, MT, 59717; and assistant professor, Math and Computer Sciences Department, Montana Tech, Butte, MT, 59701. |
Abstract |
| We evaluated the impact of packstock grazing on a dry, upper timberline meadow. Horses were picketed on 15 m ropes for different durations, months, and frequencies over 3 summers. Before horse grazing, we estimated vegetal, bare soil, litter, rock, and moss cover, measured grass and forb plant heights, counted grass and forb stems per area, and determined the percent of plants grazed. These measurements were repeated 1 growing season later. More bare ground and less litter and vegetal cover were recorded 1 year following single 8- or 18-hour grazing events. Single grazing events of 4-hour duration had no effect on cover. Decreases in vegetal cover were associated with reduced stem numbers. Eighteen hour picket durations reduced subsequent year production of grass and forb stems. We discuss the difficulties encountered in this study, including estimates of necessary sample sizes, to help in the design of future studies. |
| Key Words: horse, grazing response, ground cover, plant growth. |