The influence of repeated prescribed fire on decomposition and nutrient release in uneven-aged loblolly–shortleaf pine stands

Abstract

Abstract Background Repeated use of prescribed fire in Southern US pine stands has the potential to alter litter quality as well as forest floor mineralization, which may reduce nutrient availability. There are few studies that have investigated the effects of prescribed fire on litter decomposition in stands with frequent, partial harvests. To better understand the effects of the long-term use of prescribed fire coupled with periodic harvesting, we monitored foliar litter mass loss and nutrient dynamics in three loblolly pine (Pinus taeda L.)–shortleaf pine (Pinus echinata Mill.) stands located in southeastern Arkansas, USA. A reciprocal transplant method and the litterbag technique were used to determine the effects of litter source (litter quality) and litter location (environmental conditions) on decomposition. Results Long-term use of prescribed fire in periodically harvested stands had minimal influence on mass loss and nutrient dynamics. The proportion of foliar litter remaining after approximately 16 months did not significantly differ by litter source or location. Decay constants associated with litter incubated during the first 30 days of the study differed significantly by litter source, but thereafter were similar. Initial concentrations of phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) were 13 to 22% greater for litter originating from the burn than for litter originating from the control treatment, but differences in nutrient concentrations were not found to alter decomposition or nutrient dynamics. Thirteen percent more K was lost from litter originating from the burn compared to litter originating from the control treatment, but losses of other nutrients did not differ between litter sources. Soil and forest floor environmental conditions did not differ between treatment locations, which likely contributed to the similar decomposition rates in the two treatment locations. The rapid growth of understory and the maintenance of similar canopy conditions as a result of harvesting were likely responsible for the similarity in environmental conditions. Conclusions Repeated dormant season prescribed fire in these loblolly–shortleaf pine stands did not appear to have a substantial influence on mass loss or nutrient release from litter. Land managers who utilize prescribed fire with periodic harvesting in relatively mesic upper Gulf Coastal Plain pine forests likely will not alter litter decomposition or nutrient dynamics.