In the early 1800s, upland plant communities of north-central Mississippi contained open, self-replacing stands of fire-tolerant oaks. Most oak woodlands protected from fire and other disturbances converted to closed-canopy oak-hickory-gum forests in the 20th century. Recent evidence suggests that flammable warm-season grasses, largely absent from fire-suppressed forests today, were a significant component of the groundcover historically. Restoring these grasses to the understory would be faithful to the original composition of these communities and could provide land managers with greater flexibility in the timing of effective prescribed burns. To examine survival responses of transplants of Schizachyrium scoparium (little bluestem) and Andropogon virginicus (broomsedge) to restoration treatments and to experimental litter removal, we utilized an existing restoration experiment initiated at Strawberry Plains Audubon Preserve in 2004. The experiment included prescribed burning and tree thinning paired with controls at two sites. Each site contained two or more 10 x 30 m plots, subdivided into 7 to 13, 1.5 x 1.5 m sampling subplots each containing two pairs of transplants. One transplant of each pair was raked after transplantation and after peak leaf fall. Survival responses to experimental litter removal and environmental variables related to restoration treatments were analyzed statistically using ordinal regression.
Results/Conclusions
As expected, survival of little bluestem transplants increased with decreasing canopy density and decreasing leaf litter, both of which were associated with recent fires and thinning treatments. Leaf-litter removal did not increase survival, however, nor did it interact with either pre-treatment leaf litter depth or canopy density. These results suggest that little bluestem benefits from at least one of the conditions expected historically: increased light. It may also benefit from fire-mediated reductions in leaf litter, but if so, fire effects are not mimicked by mechanical removal of leaf litter. Furthermore, repeated burning might not have a positive effect on this species within more-or-less closed-canopy conditions. In contrast to little bluestem, broomsedge survival was affected by litter removal, but in complex and unexpected ways, none of which was consistent with a positive response to canopy thinning or fire. Broomsedge is an early colonizer of disturbed sites, whereas little bluestem is more likely than broomsedge to be associated with fire-maintained savannas and woodlands. For restoration on large tracts of relatively undisturbed forest, little bluestem may prove to be a better transplant candidate.
