Control of Aspen Regrowth by Grazing with Cattle

Abstract

Aspen (Populus tremuloides) forest occupies potentially useful grazing land in the aspen parkland of western Canada, and is expanding. The replacement of forest with grassland involves the removal of trees and the control of suckers which invariably emerge following overstory removal. The control of aspen suckers by heavy browsing with cattle may be a useful technique especially in the presence of logs and stumps. In order to evaluate the effectiveness of browsing by cattle, aspen forest was burned and seeded to forages, after which the regrowth was heavily grazed by cattle either after emergence of suckers (early) or just prior to leaf fall (late). Grazing treatments were conducted over two growing seasons. A single heavy late grazing practically eliminated aspen regeneration, and two quite different plant communities resulted from the two grazing regimes. After the first year, the plant biomass in early-grazed plots consisted of 29% aspen and 28% grass (mainly sown species), while late-grazed plots had only 2.5% aspen and 18% grass, with a higher proportion of shrubs, especially snowberry. Trends established after the first year were still evident after the second year. The results indicated that heavy browsing by cattle in August may be an effective technique for control of aspen suckers following initial top kill.