The BOREAS Information System
Trace Gas Biogeochemistry (TGB)

TGB-1: Magnitude and Control of Trace Gas Exchange in Boreal Ecosystems

P.I.(s): Patrick M. Crill -- University of New Hampshire

Objectives: To examine the role of boreal soils in trace gas exchange with the atmosphere. There are three objectives to this study:

  1. To quantify the exchange rates of CO, N2O, CO2 and especially CH4 with representative, drained upland soil sites in the boreal forest over an entire biological "active" season.
  2. To quantify the relative contributions of upland soils and lowland beaver ponds and their associated wetlands in the regional CH4 cycle.
  3. To develop techniques that will allow confident scaling of flux measurements from local to landscape to regional scales.

Location: NSA
Sites: NSA-OJP, NSA-YJP, NSA-Beaver Pond, NSA-OBS
Duration: May-September 1994

TGB-1 Pictures

The 3 meter flux tower at the NSA beaver pond

TGB-1 Data Sets

  • Gas Flux CH4 and CO2
  • Gas Flux SF6
  • Tracers Rn
  • Soil Profile CH4 and CO2
  • DIC
  • NEE

  • Get some TGB-1 data using FTP (BOREAS Investigators only, password required). [FTP Help]

    TGB-1 BOREAS Operations 1994

    To quantify and determine the controls on the exchange of trace gases, especially methane (CH4) and carbon dioxide (CO2), between boreal upland environments and beaver ponds with the atmosphere.

    CH4 and Respiratory CO2 Fluxes

    Types of Data and Equipment:
    Fluxes were measured with a dark chamber technique in which a chamber was fit to the collars (or floated on the water surface) to begin the flux and aliquots of headspace air were removed at four to five minute intervals for 20 minutes with 60 ml polypropylene syringes. CH4 and CO2 concentrations in the syringes were measured at the Hayes Rd lab within 12 hours of collection using gas chromatography (flame ionization detection for CH4 and thermal conductivity detection for CO2). Fluxes were quantified by regressing the concentration changes against time; n=5 for CH4 and n=3 (ambient then first two syringe samples) for CO2. Temperature was measured in each chamber. Temperature was also measured at 0-2 cm, 10 cm and 20 cm at thermocouple arrays installed with each group of collars.

    Summary of Places and Times of Measurements:

    CH4 and CO2 Soil Concentrations

    Summary of Places and Times of Measurements:

    Types of Data and Equipment:
    CH4 and CO2 depth profiles to ca. 90 cm were also taken weekly from tubes installed during August 1993 at OJP Moss and Lichen sites. Temperature (thermocouple) and TDR moisture profiles (w/ TGB-4) were continuously monitored at these sites during the same period. At the other sites, samples were taken by inserting a 1/8" stainless steel tube to depth and pulling gas. CH4 and CO2 concentrations in the syringes were measured at the Hayes Rd lab using gas chromatography.

    Continuous CH4 Concentration and Flux by Gradient Methods

    Summary of Places and Times of Measurements:

    Types of Data and Equipment:
    Ambient air samples were analyzed from two heights on the NSA-OJP (30m and 16.5m) and the beaver pond tower (1.75m and 0.25 m). A continuous stream of air pumped from each height was automatically sampled and injected at approximately 6 minute intervals onto gc-fid s that were kept in continuous operations at the sites; one in the instrument shack, the other in a tent). A standard was run between each ambient injection. Precision (as coefficient of variation of a half hour running average of the standard) was about 0.18%. Five discrete determinations of the gradient were then combined into half hourly averages and the gradients were multiplied by transfer coefficients determined by heat, moisture and turbulent fluxes in order to calculate mass flux of CH4.

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    Last Updated: November 5, 1997