Invasive grasses are driving intense fires in many areas across the globe, but the impacts of native versus invader fueled fires on community assemblages is poorly understood. We compared fuel loads in native sandhill communities to areas dominated by invasive cogongrass (Imperata cylindrica) in Florida. Then, we conducted a field experiment to examine how native or invasive fuel loads affected soil heating and subsequent emergence of seven native and five invasive sandhill plant species.
Results/Conclusions
Average fuel loads were 84% greater in cogongrass-invaded communities than native communities. Soil heating (duration temperatures >60° C) increased and seedling emergence decreased with fuel loads, and these relationships were similar across the overlapping range of fuel loads for native and invasive fuel types. However, longer durations of soil heating produced at the higher fuel loads commonly generated by cogongrass further reduced seedling emergence for most species. Cogongrass emergence was not significantly affected by fuel loads in either native or invasive fuel types, indicating that cogongrass is tolerant to the more intense fires it generates. Our results demonstrate that intrinsic properties of these native and invasive fuels are similar, but that higher fuel loads in invaded areas can increase soil heating and reduce post-fire seedling emergence. By increasing fuel loading and soil heating, invasions may alter post-fire community assemblages and facilitate invader dominance at the expense of native species.