Widespread exclusion of fire across eastern North America has resulted in shifts in composition that have cascading effects on contemporary fire regimes. Cessation of frequent fires enabled fire-intolerant trees (hereafter “mesophytes”) to establish in many formerly fire-prone savannas, woodlands, and forests dominated by fire-tolerant tree species (hereafter “pyrophytes”). This shift toward mesophytic trees has far-reaching consequences for fuels and fire regimes. We used a series of laboratory burning and drying experiments to compare the flammability of mesophytes and pyrophytes. Our objectives here were to compare the flammability and drying rates of litter from pyrophytes and mesophytes.
Results/Conclusions
Pyrophytic oaks (Quercus spp.), hickories (Carya spp.), and pines (Pinus spp.) burned with greater intensity than co-occurring mesophytes. In addition, mesophytic litter adsorbed more water and dried more slowly, further diminishing the flammability of these species. Combining drying and burning experiments further separated the mesophytic litter from the pyrophytes. Red maple (Acer rubrum) and sweetgum (Liquidambar styraciflua), two dominant mesophytes in the region, played overwhelming roles in the diminished fire behavior reported in field studies. We also present data from field prescribed fires illustrating the effects of the loss of herbaceous fuels (primarily grasses and native asters) on community flammability. These results highlight the dampened effects of current fire reintroduction experiments and suggest that land management treatments designed to restore the functional role of fire in eastern deciduous forests and woodlands face impediments due to the legacy of fire exclusion.