Thursday, 13 July 2006

Fifty Years of Prescribed Fires Slow Podzolization and Increase Phosphorus Availability in a Spodosol (Podzol) in Florida, USA.

Ralph J. DiCosty, Mac A. Callaham Jr., and John A. Stanturf. USDA Forest Service, Forestry Sciences Laboratory, 320 Green Street, Athens, GA 30602-2044

In the southeastern United States, prescribed fire is used to maintain fire-dependent ecosystems and reduce the risk of severe wildfires. We evaluated the role of fire in soil genesis by sampling Spodosols (podzols) under pine forest in Florida, where different prescribed fire regimes (unburned, annually burned, and burned every four years) have been in place for 50 years. Acid ammonium oxalate was used to extract noncrystalline aluminum (Al) and iron (Fe) as well as available phosphorus (P). Fire increased noncrystalline Al and Fe in the A horizon and decreased noncrystalline Fe in the B horizon, suggesting that fire is slowing podzolization. The mechanism of these changes is discussed, but remains uncertain. Available P increased with fire in both the A and B horizons, evidently due to mineralization (during fire) and subsequent leaching of P in the forest floor.

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