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

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.

Comparing the Effects of Prescribed Burning on Soil Chemical Properties in East Texas Forests with Longleaf and Other Southern Pines in the Overstory

“…The significant changes in the extractable phosphorus concentration in our study were inconsistent with other findings [5,7], who reported no difference in phosphorus after a burn. Even though we detected a significant decline in the available phosphorus, the concentrations of phosphorus in the soil were relatively low across the different times and not at a more available level of concentration in the soil [18].…”

“…Even though we detected a significant decline in the available phosphorus, the concentrations of phosphorus in the soil were relatively low across the different times and not at a more available level of concentration in the soil [18]. Significant changes in potassium agreed with [5], who found a significant increase in potassium after a fire, but contradicts [7], who found no significant change in potassium after a burn. Even though there were significant differences between time frames and burn intervals, they were not enough to effectively change the level of potassium [18].…”

“…Soils that are severely burned tend to have lower nitrogen levels and higher calcium levels than unburned soils due to volatilization. Also, in a typical prescribed burn, potassium, magnesium, and phosphorous do not usually significantly change after a burn [5][6][7]; however, a severe fire could cause mass amounts of nutrient volatilization, or nutrients going into the soil may not become bioavailable and remain unused until they dissolve in the soil water and can be taken up by plants [8,9]. Fire can cause nutrients to become more mobile, either entering into the soil and remaining within the range of plant roots or leaching down into the soil profile and into the ground water [1,[7][8][9][10][11]; however, a single low-intensity burn does not usually change the nutrient availability in soils.…”

Litter Decomposition and Nutrient Dynamics in Fire-Affected Larch Forests in the Russian Far East

“…Postfire litter decomposition in low-latitude coniferous forests is characterized by contradictory results. A litterbag study of pine litter decomposing in Arkansas, USA, revealed a minimal difference in mass loss and nutrient dynamics between burned and control forests [31]. Other research even found enhanced decomposition in a postfire period in the one-seed juniper woodland of New Mexico, USA [32].…”

Comparative Dynamics of Nutrient Release through Litter Decomposition in Eucalyptus grandis Hill ex Maiden and Pinus taeda L. Stands

“…Its loss mainly occurs through leaching from the decomposing residues [9,39], being easily removed even in early stages of the process [40]. Releases of this nutrient have been evidenced in litter of different species of Eucalyptus and Pinus [3,[41][42][43].…”