Document: JUL-3-30-35

The isotopic composition of ecosystem respiratory fluxes.

FESSENDEN, J.E.* and J.R.EHLERINGER

University of Utah, 257 S 1400 E, Salt Lake City, UT 84112-0840 1

Abstract:
The isotopic composition of ecosystem respiration was measured over the course of a year in old growth and regenerating Pseudotsuga menziesiiecosystems in the Pacific Northwest. Seasonal variation in the carbon isotope ratio of ecosystem respiration appears to be correlated with changes in plant water status. Large differences in the carbon isotope ratios of respiration occurred in El Nino versus La Nina years, with the indication of higher intercellular carbon dioxide concentrations occurring within the forest during the La Nina year. The carbon isotope ratios of ecosystem respiration in regenerating forests exhibited higher intercellular carbon dioxide concentrations than were observed in the old-growth forest under similar environmental conditions.

Keywords: ecosystem respiration, carbon isotopes

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This abstract is being presented at: 11:15 AM in session:
Oral Session #9: Respiration and Isotopes.