RESPONSE OF BIG BLUESTEM (ANDROPOGON-GERARDII-VITMAN) TO TIMING OF SPRING BURNING

Spring burns were conducted at four day intervals from 6 April through 20 May 1988 on a reestablished tallgrass prairie in eastern Nebraska. Growth and flowering responses of big bluestem (Andropogon gerardii V itman) were measured during October. Flowering stem height and floweri ng stem number increased significantly (P < 0.05) on areas burned on e ach of two, successive four-day intervals after 12 May. Plants on area s treated before 12 May showed no such response. The closely timed, bu t significantly different, responses emphasize the importance of caref ul attention to specific time of burning and associated plant growth s tatus. This is particularly relevant when interpreting the effects on such broadly defined treatments as ''Spring burn.'' Further, this stud y suggests that there may be some activity, either environmental or ph ysiological, that changes dramatically over as few as four days and th at significantly affects big bluestem.