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Terrestrial Ecology (TE)

TE-5: Vegetation-Atmosphere CO2 and H2O Exchange Processes: Stable Isotope Analyses

P.I.(s): James R. Ehleringer -- University of Utah; Larry B. Flanagan -- University of Lethbridge
Collaborator: J. Renee Brooks

Objectives: The objectives of this project are:

The first two objectives will be accomplished by combining leaf gas exchange measurements with measurements of the concentration and isotopic composition of CO2 in flask samples of air collected diurnally at different vertical positions within a forest canopy. Water source use will be determined by analysis of the stable isotopic composition of water extracted from stem xylem tissue. The carbon isotopic composition of cellulose from tree rings will be used to reconstruct past temporal patterns of gas exchange.

TE-5 Data Sets

  • Air Stable Isotope
  • CO2 Profile
  • Gas Exchange
  • Leaf Carbon Isotope
  • Meterological
  • Tree Ring

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    TE-5 BOREAS Operations 1994


    1. to determine the influence of vegetation on changes in the carbon and oxygen isotopic composition of atmospheric CO2.
    2. to determine the extent of recycling of CO2 within forest canopies.
    3. to determine the water sources used by different tree species within a growing season.
    4. to reconstruct past temporal patterns of leaf gas exchange (ratio of assimilation to stomatal conductance) using cellulose from tree rings.

    Summary of Places and Times of Measurements:
    Sites visited: SSA-OJP, SSA-OA, SSA-OBS, NSA-OJP, NSA-UBS, NSA-OA.

    Types of Data Collected:

    1. d13C and d18O of Atmospheric CO2 was collected over a diurnal period for each site during each IFC.
    2. Water Source Data: stem, leaf, soil and atmospheric water was collected at each site for each IFC.
    3. Leaf d13C was measured for the 10 most dominant species at each site.
    4. Meteorological and continuous CO2 data. Meteorological: 9m and 1m PPFD, 9m and 1m air Temperature, RH, 10 cm and 20 cm soil temperature. [CO2] at 9m, 3 m, 1 m, 0.5m, 0.25m, and 0.05m, over at least 24 hrs., usually more. Note: No RH data for NSA-OA IFC-3, due to rodent problems.
    5. Soil Data
      • Soil Respiration Rates
      • d13C and d18O of Respired Carbon
      • d13C of Soil Carbon
      • d18O of Soil Water
    6. Photosynthesis Data
      • IFC-1, Daytime Diurnal data were collected at SSA-OBS, SSA-OJP, NSA-OJP and NSA-UBS.
      • IFC-2, Daytime Diurnal data were collected at SSA-OJP, SSA-OBS, SSA-OA, NSA-OJP, NSA-UBS, and NSA-OA.
    7. Disks for Tree Ring analysis and d13C of Cellulose to accomplish objective 4. d13C of Cellulose will only be measured for trees at NSA-OJP and SSA-OJP.

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    Last Updated: October 29, 1997