Shift Toward Mesophytic Species in Oak Forests May Limit Fire Reintroduction
Exclusion of fire from eastern hardwood forests is a leading hypothesis for oak replacement by shade tolerant and more mesic species, especially red maple. In a twist on this story, the change in species composition itself may complicate the use of fire for oak ecosystem restoration. Are fuel beds derived from mesophytic litter less likely to carry fire and more likely to burn at lower intensities than beds derived from oak litter? To examine the effects of litter species composition and topography on fuel beds and fire, Forest Service researchers conducted a common garden experiment in southeast Ohio. Each garden included beds composed of mostly oak and mostly maple litter. Fuel beds that developed from mesophytic litter decayed more rapidly and packed more densely than beds derived from oak litter. In turn, combustion tests and models suggested that mesophytic beds would be less likely to carry fire and burn less intensely than oak beds. Topographic effects were independent of litter source effects with sunnier and drier sites having more fuel and drying more quickly than shadier and wetter sites. The results and ongoing work suggest that the transition to mesophytic species in southeast Ohio may reduce fire’s effectiveness restoring oak ecosystems.