Document: LOR-3-59-111

Species' constraints limit ecosystem response to nutrients on an ombrotrophic peat bog.

JOHNSON, L.C.*, J.COLES and W.H.DAMMAN

Kansas State University, Manhattan, KS 6506-4901 USA ¹

Abstract:
Peat bogs contain nearly 1/3 of the global soil carbon stocks. Yet, controls over productivity and decomposition in peat bogs remain poorly understood. A 4-year fertilization experiment was aimed at: 1) assessing single or multiple nutrient limitation (N, P, N+P) to productivity and decomposition in an ombrotrophic peat bog, and 2) determining patterns of nutrient limitation among dwarf shrub species. Application rates were 10 gN/m² N and 5g P/m² annually. Results indicate strong nutrient use complementarity among species; Ledum was co-limited by N and P, Kalmia by P alone, and Gaylussacia by N alone. Chamaedaphne did not respond to either N or P, and may be limited primarily by light. Thus, species' constraints limit ecosystem response to added nutrients. Laboratory incubations of leaf litter from the dominant dwarf shrubs and of peat soil from the nutrient amended plots assessed nutrient limitation on decomposition. C mineralization of soil showed a slight increase with added N, but decreased by 30% with addition of P. Leaf litter from the 4 dominant species showed no change in C mineralization expressed on a mass basis, but strong species' specific effects on C mineralization became obvious when results were expressed on an areal basis. Thus, our study elucidates the unique and individualistic role that each species plays in determining and constraining ecosystem productivity and decomposition.

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This abstract is being presented at: 1:45 PM in session:
Oral Session #67: Decomposition Processes.