Restoring Perennial Warm-Season Grasses as a Means of Reversing Mesophication of Oak Woodlands in Northern Mississippi

摘要

Fire suppression has removed an important ecological force previously responsible for shaping many plant communities throughout the world. Upland areas of north-central Mississippi that have been protected from fire are now closed-canopy forests including species known to be uncommon as bearing/witness trees in upland portions of the landscape (historically off-site species) and sparse ground cover vegetation. Anecdotal evidence suggests that warm-season grasses were prevalent in the understory of these communities, which could have provided more consistent fuel. We corroborate the historic presence of these grasses by looking at their natural co-occurrence with oak regeneration (a requisite of self-replacing stands of oaks found historically). Restoration of these communities has typically focused on burning and off-site tree thinning. Utilizing a restoration experiment implementing these treatments, we found significantly reduced understory leaf litter in treatment areas. To test which variables associated with restoration treatments were most important for the survival of these grasses, we measured the effect of leaf litter removal and its interaction with environmental conditions on the survival of transplanted shoots. Survival of little bluestem increased with decreasing canopy density and decreasing leaf litter. Leaf-litter removal did not increase survival, nor did it interact with either pre-treatment leaf litter depth or canopy density. These results show that little bluestem benefits from conditions expected historically: increased light and possibly fire.