RESPONSE OF EARLY-FLOWERING AND LATE-FLOWERING PLANTS TO FIRE SEASON IN EXPERIMENTAL PRAIRIES

Fire maintains tallgrass prairies, but fire season is virtually unexplored as a formative influence of prairie floristics. Replicated mid-July burns, simulating the peak of lightning-caused fire in natural grasslands, strongly influenced species composition and cover in experimental restorations in southern Wisconsin. Perennials that flowered before mid-July showed only 17% cover in unburned plots and 6% in plots burned in March, but 46% cover in plots burned in mid-July. Late-flowering species dominating the remnants managed with dormant-season burns accounted for 80% cover in unburned plots and 92% cover in plots burned in March, but only 47% cover in plots burned in July. Management practices that employ dormant-season burns may produce quite different communities than those maintained by midsummer burns that simulate the timing of lightning fires.