J6.4 Environmental control of forest ecosystem δ13CO2 discrimination

Wednesday, 30 May 2012: 11:15 AM
Press Room (Omni Parker House)
David Y. Hollinger, USDA Forest Service, Durham, NH; and C. T. Lai, W. J. Massman, K. L. Clark, K. Novick, F. Meinzer, and K. Bible

We used Picarro isotopic CO2 analyzers to make profile measurements of 12CO2, 13CO2, and water vapor at 5 forested AmeriFlux sites (Wind River, GLEES, Howland, Silas Little, and Coweeta) across the continental U.S., starting in late 2010. We describe our experimental system and validation efforts. Concentration data and convective boundary layer budgeting methods are used to infer regional surface-atmosphere CO2 exchange. Whole ecosystem discrimination varied markedly at diurnal and seasonal timescales, reflecting the influence of vapor pressure deficit, temperature, and light. Comparison of Howland results to nearby tall tower data suggests that these data reflect regional scale patterns of CO2 discrimination.
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