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TG-04 Abstract

Radon-222 and Stable Carbon Isotope Tracing of Carbon Exchange and Trace Gas Fluxes in Old Growth and Selectively Logged Amazonian Forests

Christopher S. Martens — University of North Carolina at Chapel Hill (US-PI)
Osvaldo Luiz Leal de Moraes — UFSM - Universidade Federal de Santa Maria (SA-PI)
Marcelo Zacharias Moreira — CENA - Centro de Energia Nuclear na Agricultura (USP) (SA-PI)
Reynaldo Luiz Victoria — CENA - Centro de Energia Nuclear na Agricultura (USP) (SA-PI)

We propose

to continue studies of the rates and mechanisms of processes controlling carbon

dioxide and trace gas fluxes at old growth forest and selectively-logged forest

sites in the Tapajos National Forest and at pasture sites south of Santarém,

Pará, Brazil using a unique suite of state-of-the-art radon and stable isotope

measurements. The continuing work is fully integrated with LBA-ECO tower eddy

covariance flux, forest canopy gas inventory and soil gas flux studies led by

Keller et al. (TG-07), Goulden and Rocha (CD-04), and Wofsy et al. (CD-10). In

addition, we propose to make tower and portable field radon measurements that

will contribute to larger scale studies of gas transport processes associated

with the development of nocturnal and convective boundary layers led by

Fitzjarrald and Moraes (CD-03) and other LBA-ECO Science Team members. Brazilian

collaborators and students lead or are involved in many aspects of the proposed

project. All of the proposed radon-222 and stable isotope measurements will be

made in Brazil except for limited laboratory intercalibration studies that are

essential for achieving maximum analytical accuracy. The proposed research will

quantitatively address two theme areas in LBA-ECO: Carbon Dynamics and Trace Gas

and Aerosol Fluxes. The proposed work is focused on four primary objectives:

  1. Quantification of net CO2 and trace gas exchange rates

    between the atmosphere and old growth and selectively logged forests and

    pastures utilizing tower and soil flux radon-222 measurements. Direct

    comparison of exchange rates from radon versus eddy covariance rates using

    the same canopy gas inventory measurements.

  2. Radon tracing of periodic and spatially inhomogeneous

    vertical and horizontal gas transport on a regional scale up to the top of

    the convective boundary layer (CBL) including quantification of nocturnal

    and CBL vertical scales and inhomogeneity and initial investigations of

    horizontal air drainage from the FLONA Tapajos.    

  3. Quantification of CO2 and trace gas soil fluxes and

    production/consumption rates versus height within the forest canopy using

    measured radon-222 flux divergence. Direct comparison of these rates with

    results from auto-chamber soil flux and canopy respiration rate


  4. Utilization of methane canopy inventory, soil flux and

    d13C-CH4 measurements to distinguish the sources, canopy height source

    distribution, and net flux of methane from soils and dispersed forest

    sources to the atmosphere.

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