Response of Livestock to Riparian Zone Exclusion

Abstract

Fencing has been proposed as the best alternative for rapid restoration of streamside riparian zones. In this study the major portion of the streamside riparian zone was excluded by fencing. Use by cows with calves and by yearlings was evaluated on the remaining portion of the riparian and upland zones during the summer grazing season. Regardless of aspect, both classes of livestock generally selected the riparian zone over the uplands throughout most of the summer grazing season. Both classes of livestock reversed their selection in favor of upland vegetation in the latter part of the season. Slopes less than 35% were preferred throughout the grazing season. Cows were more selective in use of certain plant communities than yearlings and, contrary to usual findings, distributed themselves over the range better than yearlings. Neither salt placement nor alternate water location away from the riparian zone influenced livestock distribution appreciably. Throughout the Pacific Northwest, riparian zones make up a small part of the total land base, yet receive a disproportionately large part of the resource in forest use (Thomas et al. 1979). Due to the favorable moisture, riparian zones surpass other habitats in terms of productivity and use. Recreation, timber harvest, road and railroad construction, and grazing by both wildlife and domestic livestock have a dramatic impact on this highly productive zone. Land managers are under pressure to improve water quality and maintain or enhance anadromous fisheries. The Federal Water Pollution Control Act (1972) requires that by 1983, all waters on public lands will be suitable for recreation and propagation of fish, shellfish, and wildlife; and the elimination of pollutant discharge into navigable water will be required by 1985. The 1972 Act also stipulates that the Environmental Protection Agency will be responsible for monitoring sources of point and non-point pollution. All animals on open ranges are a potential source of nonpoint pollution. The literature of range management is essentially devoid of information specific to the management of riparian zones. The impacts associated with livestock grazing in the riparian zone have become a subject of controversy in recent years (Carothers 1977). Potential solutions to preconceived problems are only now being formulated and tested. Cattle (Bos faurus) prefer the diversity, quality, and succulence of vegetation found in riparian zones (Ames 1977). The relationship between the microclimate of an area and cattle use is not well documented. The common solution has been to fence livestock out of the riparian zone. This approach is expensive, both in terms offencing costs and loss of forage. Other less drastic approaches, if successful, would be preferred. This study is part of a larger effort to accumulate information essential to development of livestock grazing systems that could protect riparian vegetation from overuse by cattle. Author is wildlife biologist, U.S. Dep. Agr. Forest Service, Pacific Northwest Forest and Range Exp. Sta., Range and Wildlife Habitat Laboratory, Route 2, Box 2315, La Grande, Ore. 97850. 760 The objectives of this study were to: 1. Determine differences in use patterns of yearling cattle and of cows with calves in pastures containing both riparian and upland mountain range plant communities, 2. Evaluate behavioral responses of cattle that are excluded from the riparian zone by fencing, 3. Determine differences in use between yearlings and cow-calf pairs between cover types on north and south aspects, and 4. Determine differences in 1,2, and 3 above due to the periods within the grazing season (time periods 1, II, and III).