Invasion of a non-native forb reduces flammability in a fire-dependent ecosystem

Fire and grazing are two of the most common global disturbances that maintain and promote many grassland ecosystems worldwide. The presence of non-native, invasive plant species can alter fire regimes through changes in fuel properties that affect native vegetation in many ecosystems and are a leading threat to biodiversity and ecosystem function. Sericea lespedeza (Lespedeza cuneata), a non-native, invasive forb frequently present in many North American tallgrass prairies, may reduce flammability by altering the fuel bed moisture and structural characteristics to reduce fire in this fire-dependent ecosystem. The goal of this research was to examine the influence of sericea lespedeza on fuel bed structure, moisture, and flammability compared to native grassland fuels. Fuel bed burning trials, conducted in a controlled laboratory setting, tested for the effect of fuel load mass of native grass and sericea lespedeza litter, proportion of sericea fuel load, and fuel moisture content on flammability metrics. Regardless of moisture content, sericea lespedeza reduced flammability and reduced maximum fire temperatures by as much as 500 degrees C. Sericea lespedeza poses a major threat to North American tallgrass prairies by decreasing flammability of fuel beds through increased fuel bed density and moisture retention.