Document: GRE-3-59-106

Nitrogen mineralization in soils of northern hardwoods and oak pine stands.

BONITO, G.* and B.HAINES

University of Georgia, Athens, GA 30602 USA ¹

Abstract:
Nitrogen mineralization rates at the Coweeta Hydrologic Lab, N.C. are higher at the highest elevation. Reaction rates usually decrease with decreasing temperature. Temperature and growing season decrease with increasing elevation. Thus, we expect nitrogen mineralization to decrease with increasing elevation. Causes of high mineralization rates at higher elevation are yet to be explained. Alternative hypotheses to explain high mineralization rates at higher elevation, Northern Hardwoods site (NH) compared to the Oak-Pine site (OP) include: 1) differences in biological communities; 2) shorter growing season; 3) increased moisture; 4) higher soil pH; and 5) mineralization promoter in decomposing herbs, leaf litter or soil of high elevation site. The promoter hypothesis was tested by measuring ammonification in 30 day incubations of OP and NH soils to which were added aqueous extracts from herbs, leaf litter, soil or deionized water. All incubations of OP soil showed net loss of NH₄⁺ which can be attributed to nitrification or denitrification. Incubations of NH soils found the highest ammonification rates. Ammonification rates in the NH soils were highest in those receiving extracts from the NH litter (2.2 mg N/kg) and the OP (1.2mg N /kg soil).

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This abstract is being presented at: 3:30 PM in session:
Poster Session #15: Nutrient Cycling.