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Abstract
In the southeastern United States, the function and stability of pine ecosystems depends on frequent low intensity fires. Critically, fire suppresses hardwood competition by killing aboveground stems. Previous long-term studies correlated early growing season burns with higher understory mortality when compared to dormant season burns. Seasonal differences in mortality from insufficient carbon reserves in roots after leaf flush were posited as the mechanism; however, this has not been explicitly tested. In this experiment, two-year-old pot-grown sweetgums (Liquidambar styraciflua) were burned in the dormant season (February), and growing season (May), or left unburned. By the end of the first post-burn growing season, mortality was significantly higher after the dormant season burn than the growing season burn and unburned trees had nearly twice the mass of either the burned treatments. Starch concentrations were similar across treatments. Our results indicate the top-kill of dormant plants can be more damaging than growing season top-kill.