Monday, 17 November 2003: 1:30 PM
Changes in nutrients and biomass immediately after a low-intensity prescribed fire in an uneven-aged loblolly pine stand
Jennifer J. Hooper, University of Arkansas, Monticello, AR; and H. O. Liechty and M. G. Shelton
Nutrient levels and mass of the understory vegetation and the forest floor were measured in loblolly pine (Pinus taeda L.) stands within the Gulf Coastal Plain of Arkansas prior to and following a prescribed fire. These stands were strip burned during the dormant season under conditions of moderate humidity and low ambient air temperature. Since these stands were burned on a 1- to 4- year interval over a 20-year period, fuel loading was low, with an average of 9 Mg ha-1 within these stands. The mass of the combined forest floor and understory vegetation following the fire was approximately 50% of that prior to burning. The low-intensity fire conditions and the high moisture content in the forest floor (33%) and understory vegetation (30%) may have contributed to the minimal loss of mass during the fire.
Comparisons were also made between pre- and post-fire macronutrient concentrations and contents of the forest floor and understory vegetation. Although nutrient contents of both forest components were reduced by the fire, concentrations of all macronutrients, except K, were increased in the forest floor. Reductions in K concentration within the forest floor may be attributed to leaching during a precipitation event that occurred immediately following the fire. Increases in concentrations of N, P, Mg, and Ca were probably related to the low fire intensity observed during the prescribed fire. In addition, burning of the understory may have increased nutrient concentration from added ash and charred vegetation to the forest floor. Although changes in macronutrient levels were significant immediately following the prescribed fire, long-term results within these study sites demonstrated no or only a minimal change in nutrient regimes between stands which had no prescribed fires and those burned repeatedly on a 1-4 year interval for a 20-year period.