Prescribed fire every two to five years is applied to reduce understory fuel, favor wildlife habitat, and perpetuate the flora and fauna of pine ecosystems. Frequent prescribed fire is vital to longleaf pine (Pinus palustris Mill.) ecosystem function and is an important part of ongoing efforts to restore longleaf pine forests in the southeastern United States. One means of avoiding stemwood growth loss by fire is timely reestablishment of scorched foliage.
Two studies conducted on the Kisatchie National Forest in central Louisiana, USA showed that the foliage biomass of heavily scorched longleaf pine saplings was re-established by one growing season after spring or fall fire. At one of these studies, we evaluated relationships between season of fire and three carbon endpoints: reestablishment of scorched foliage, and seasonal storage and mobilization of starch and total phenolic concentrations in the taproot, stem, and terminal branch tip. Our objectives were to determine if post-scorch foliage reestablishment or relationships between foliage regrowth, and the dynamics of starch and total phenolics in sapling tissues differed by the season of prescribed fire.
Results/Conclusions
In spring when stored starch was at its highest concentration, foliage recovery from crown scorch was correlated with starch mobilization. It is likely, therefore, that foliage reestablishment after spring crown scorch benefited by both stored starch and photosynthate produced in residual, unscorched foliage. In contrast, starch was nearly depleted in fall making foliage regrowth after fall crown scorch primarily dependent on current photosynthate. With the exception of an accelerated mobilization of starch for two months after spring burning, seasonal starch dynamics did not differ between unburned and spring burned longleaf pine saplings. In contrast, average starch concentrations of the taproot, stem, and terminal branch tip during February through July after fall prescribed fire were reduced 34, 58, and 72 percent, respectively. A preliminary assessment of terminal branch tissue suggested that total phenolic concentration was not affected by spring or fall prescribed fire but was influenced by prolonged water deficit. Consequences of these starch and total phenolic responses during the period of foliage regrowth after crown scorch will be discussed.