Northern Prairie Wildlife Research Center
Institute for Wetland and Waterfowl Research, Ducks Unlimited, Stonewall P.O. Box 1160, Oak Hammock Marsh, MB, R0C 2Z0 Canada; Institute for Wetland and Waterfowl Research, Ducks Unlimited, Stonewall P.O. Box 1160, Oak Hammock Marsh, MB, R0C 2Z0 Canada; Ducks Unlimited Canada, Number 8, 5580 43rd Street, Red Deer, AB, T4N 1L1 Canada
Grasslands of southern Alberta are extensively used for cattle production. Both upland prairie and wetland vegetation provide cattle forage. Spikerush (Eleocharis palustris) is a common species of natural prairie wetlands. It thrives in shallow wetlands that get flooded by spring runoff and then slowly dry up during the summer. Because its protein content is very high, this species provides important cattle forage. Prairie wetlands also provide wetland and upland habitats for breeding waterfowl. However, in recent years, drought and intensive agriculture caused significant declines in waterfowl productivity. Increasingly, waterfowl managers work with agricultural interests, implementing multi-use habitat management strategies that benefit wildlife as well as agriculture. In southern Alberta, irrigation water can be used to fall-flood (and to maintain flooding throughout the summer) shallow wetlands favored by breeding dabbling ducks. However, the impact of such flooding on wetland vegetation, including important cattle forage species such as spikerush, is unclear. This study was designed to examine spikerush responses to fall flooding and prolonged flood periods. Such water regimes are practical in southern Alberta and would enhance waterfowl pair and brood habitats.
The experiment was conducted at the Ducks Unlimited Kitsim complex during 1988-90. In addition to the natural regime (four months flooding, eight months drawdown), we applied three fall flood treatments, all with different summer drawdown periods (10.5 months, 9 months, and the combination of 10.5 months in year 1 and 9 months in year 2). We measured changes in stem density and peak standing crop in eight basins (two replications per treatment). The impact of grazing was eliminated by fencing all study plots. Treatments had no significant effect on peak standing crop, but we detected a year effect. Mean stem density was not affected by either treatment or year. We concluded that there was no difference in spikerush response to the four water regimes. Fall flooding and prolonged summer flooding should result in healthy spikerush stands and at the same time provide attractive waterfowl habitat. However, we recommend that each basin be drawn down for at least 1.5 months each year. While treatments had no significant effect on peak standing crop or stem density, we detected a significant year effect, as standing crop decreased in all treatments between 1988 and 1990. We speculate that this decline can be attributed to the elimination of grazing in our experiment.