Brush Control on Sandy Rangelands in Central Alberta

Abstract

Balsam poplar, aspen, and willows that had invaded subirrigated sandy rangeland were treated with (1) prescribed spring burning, (2) the herbicide 2,4-D ester, and (3) prescribed burning followed by 2,4-D ester. After 5 years, burning and spraying had reduced brush the most. Brush reinvasion was occurring rapidly on all treated areas. Stand openings of about one quarter hectare in an 8 meter high poplar forest resulting from these treatments did persist for at least 5 years. Treatments were effective enough to lower the forest cover and in some cases increase forage production. Repeated burning and spraying substantially reduced the density of reinvading woody suckers. The presence of woody plants on rangeland has long been of concern to the land managers interested in increasing forage production. Woody species encroachment has been attributed to fire control, overgrazing, and farm abandonment (Friesen et al. 1965) although climatic cycles have also been influential (Bailey and Wroe 1974). Forage production could be increased if woody vegetation was reduced. The depressing effect of woody plants on grasses has been demonstrated (Bailey and Wroe 1974; Whysong and Bailey 1975). Methods of brush control have focused upon mechanical means, prescribed burning and herbicides, or some combination of these. Mechanical removal of aspen forest and replacement by forages has not been always successful in arresting aspen suckering (Pringle et al. 1973). Burning of aspen --cover is not always successful because of the discontinuous coverage of fuels and the difficulty in obtaining suitable burning conditions (Perala 1974). A single fire also fails to control aspen suckering (Horton and Hopkins 1966). However under appropriate conditions, and in conjunction with spraying, prescribed burning may be an effective range improvement tool. Foliar applications of herbicides have been used Authors are professor and research associate, Department of Plant Science, University of Alberta, Edmonton, Alberta. This research was supported by an Alberta Agricultural Research Trust grant and a National Research Council of Canada grant to the senior author. Manuscript received July 19, 1977. with some success on aspen in western Canada (Bailey 1972; Bowes 1976) indicating the usefulness of continued research in this area. The experiments reported here were designed to determine the magnitude and duration of the effects of prescribed burning, herbicide treatment, and a combination of the two on species composition, density of woody stems, and herbage production of a mix poplarwillo,w (Populus-Salix) forest which had encroached on subirrigated sandy ranges dominated by a baltic rushKentucky bluegrass (Juncus balticus1Poa pratensis) grassland.