Energy content of common fuels in upland pine savannas of the south-eastern US and their application to fire behaviour modelling

Knowing the energy content of wildland fire fuels is important for predicting fire behaviour and for interpreting the pyrogenicity of plant communities. Energy content was determined for fuel categories characteristic of south-eastern US pine savannas, specifically live herbs, 10-h fuels, broadleaf litter, fine dead surface fuels, needle litter from three pine species, and other 1-h fuels combined. Pine needles had higher energy content than the other fuels, fine litter had lower energy content than the other fuels, and all other categories did not differ from each other. Longleaf pine (Pinus palustris) needle litter had lower energy content than loblolly (P. taeda) and shortleaf (P. echinata) pines, which did not differ from each other. Measured energy contents were used to estimate energy content for total fuel loads in native and old-field pine savannas of southern Georgia and northern Florida based on data from a previous study that provided fuel loads in each fuel category. Fire behaviour was predicted using the BehavePlus 5.0.0 default and newly estimated energy contents. This comparison revealed that fire behaviour parameters in the studied native and old-field pine savannas are overpredicted using the default energy content. In savannas, energy content estimates should take into consideration the proportion of fuel types, especially tree leaf litter relative to other fine fuels, for accurately predicting fire behaviour.