Burning (wildfires and man-induced) have shaped North American prairie plant communities. On the Donaldson Pastures in the Flint Hills of eastern Kansas (central USA), the effect of timing of spring burns on vegetation yields and plant community composition on bluestem range under moderate cattle grazing was assessed over 17 years.
Vegetation was dominated by warm-season perennial grasses: big bluestem Andropogon gerardi and little bluestem A.scoparius (contributing 50-60% by basal area), Indiangrass Sorghastrum nutans, switchgrass Panicum virgatum and sideoats grama Bouteloua curtipendula 10-20%, with numerous other grasses and forbs.
Three 17.8 ha pastures were burned annually for 17 years (1950-1966) at three spring dates: early (20 March), mid (10 April) or late (1 May). A similar, unburned 24.3 ha pasture served as a control. All were cattle-grazed season long at moderate intensity (approximately 5 acres/animal unit).
Species composition (percentage of total plant basal cover) within each pasture was estimated by measuring the basal intercept of each plant along 20 to 30 randomly placed 5-m long line transects.
Range condition (poor, fair, good or excellent) was estimated annually.
Each year within randomly placed (0.86 m²) wire cages (to exclude cattle), vegetation was clipped to ground level and likewise adjacent plots open to grazing. Material was separated into forage, weeds, and mulch, dried and weighed.
Cool season species were reduced by spring burning and desirable warm season perennial grasses benefitted, as is the aim of spring burning. Likewise some weedy species, whose growth similarly initiates in late spring/summer subsequent to burns, also increased. Herbage yields were reduced by early and mid-spring burning, but late spring burn yields were similar to the control.