Quantifying recalcitrant pools of carbon are critical for understanding long-term source-sink relationships in fire frequented ecosystems, such as longleaf pine forests.  Such pools are commonly overlooked in fire-frequented ecosystems, as fires are assumed to accelerate processing and limit accumulations of coarse woody debris (CWD). Charcoal generated during fire events is extremely recalcitrant.  Moreover, heartwood in pine ecosystems of the southeast represent a significant form of passive carbon(C) that has the potential to dramatically alter turnover rates due to its high resin content and resistance to decomposition.  These different pools of C likely turnover slowly but at different rates, and the application of fire further alters the distribution of C within these pools.  This study uses both xeric and mesic burned and 5-year unburned sites to analyze the amount of C in different pools. 

Results/Conclusions

The total volume of CWD, both oak and pine, was found to be 4.73m³/ha ± 2.80m³/ha and the total mass of charcoal was 100.46 Kg/ha ± 87.79 Kg/ha.  The amount of volume and charcoal in each of the CWD pools were stump volume 0.569m³/ha ± 0.348m³/ha, stump charcoal 2.11 Kg/ha ± 1.19 Kg/ha, downed debris volume 1.58 Kg/ha ± 1.00 Kg/ha, downed debris charcoal 3.86 Kg/ha ± 2.50 Kg/ha, standing debris volume 2.58 Kg/ha ± 2.20 Kg/ha, standing debris charcoal 94.49 Kg/ha ± 85.86 Kg/ha. Despite frequently applied fire, no significant differences were observed in standing crop of woody debris or charcoal.  These results document the ubiquity of recalcitrant carbon pools across the range of longleaf pine habitats despite frequent fire. The high volumes in this study underscore the importance of documenting the standing crop and rates of turnover recalcitrant C pools.