Non-native invasive grasses are driving intense fires across the globe but the impacts of native versus invader-fueled fires on community assemblages are poorly understood. By increasing fire intensity, grass invasions might increase belowground mortality of heat-sensitive seeds and buds, thereby shifting community composition.

We compared fuel loads in native and non-native invasive (cogongrass, Imperata cylindrica) plant dominated areas of pine savannas in Florida. Then, we conducted a field experiment to examine how fuel loads and native and invasive fuel types affected soil heating and seedling emergence or resprouting of native and invasive plant species.

We found that average fuel loads in invaded communities were greater than in native communities and that soil heating, including heating duration >60 °C, maximum temperature, and heat flux >60 ºC, increased, and seedling emergence and resprouting decreased with greater fuel loads. These relationship between soil heating and fuel loads did not differ between the overlapping range of native and invasive fuel loads, but longer durations of soil heating at the higher average fuel loads of invaded communities resulted in 23% lower predicted probability of seedling emergence compared to average fuel loads of native communities. Resporuting of cogognrass, the invader responsible for fuel loading, was unaffected by soil heating. 

By increasing fuel loading and soil heating, grass invasions may alter post-fire community assemblages and facilitate invasive grass dominance at the expense of native species via an invasion-fire cycle. Fuel loads can be used to predict soil heating duration and depth and these data, combined with information on species tolerances to heating, can be used to forecast impacts of invasions on post-fire community composition. To maintain fire regimes that promote native communities and resist invader dominance, it is critical to manage invasive species that increase fuel loads.

This dataset includes soil heating measurements (Summarized_Soil_Heating_Data), fuel loads (Savanna_Fuel_Loads), experimental fuel moisture (Experimental_Fuel_Moisture_ and seedling emergence and resprouting data (Emergence_Resprouting) used in our study.