Plant community responses to prescribed burning in Wisconsin sedge meadows
In northern temperate regions, sedge meadows dominated by the tussock-sedge Carex stricta Lam. (Cyperaceae) were historically a fire-maintained community type. In two Wisconsin natural areas (Lulu Lake and Summerton), the authors assessed the effects of time since prescribed spring burning on plant composition and aboveground biomass in eight sedge meadows representing a partial chronosequence of zero to seven years since burning, plus no burning. They recorded plant species cover in line-intercept transects and measured live biomass and litter in sample plots along transects. Responses were prominent during the first two years after burning. In the Lulu Lake meadows, live biomass and annual forb cover reached their highest values during the first growing season after burning, whereas cover and frequency of perennial forbs were elevated for two seasons. Plant litter was removed by burning but returned to preburn levels in one to two years. In the Summerton meadows, where seven years had elapsed since the last fire, burned and unburned meadows did not differ in live biomass, litter, or relative cover of plant life-forms. It appears that periodic bums do not cause major shifts in the relative dominance of sedges and grasses, which are long-lived clonal perennials. However, because litter removal promotes recruitment of shorter-lived forbs, prescribed fire can enhance sedge meadow diversity by allowing plant species with different life histories to temporarily share dominance with the more abundant graminoids. Periodic seed inputs by forbs to the wetland seed bank may be a desirable fire management objective for maintaining sedge meadow diversity.