Willow Creek Flux Tower

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30 m tower
CO2 profiling system
Equipment enclosure

Forest canopy viewed from top of tower
Understory viewed from base of tower

Click here to see additional photos!

Location:  45° 48.47' N, 90° 04.72' W  (click here for topo map)
Elevation:  approx. 520 m above sea level
Annual Average Precipitation/Snowfall (Park Falls, 1961-1990):  81.8 / 126.2 cm
Annual Average Temperature (Park Falls, 1961-1990):  4.8°C
Stand age:  approx. 66 years
Species Composition:  Maple-Basswood-Ash (click here for basal area data)
Canopy height:  approx. 24.3 m
Leaf Area Index (LAI):  4.18
Average Stem Diameter at Breast Height (dbh):  25.4 cm
Soils: coarse glacial till (click here for profile description)
Established:  4 May 1998


    Rohn 45G tower (100 ft)
    CSI CR23X datalogger, 4 MB extended memory
    CSI CR10X datalogger, 2 MB extended memory
    CSI AM25T and AM416 multiplexers
    LI-COR 6262 (CO2/H2O fluxes) and 6251 (CO2 profile)
    Brailsford TD4x2NA double acting diaphram pumps, ¼" (od) PFA or Dekabon 1300 tubing, and Gelman Acro 50 teflon inlet filters
    High precision CO2 profiler (see Peter Bakwin et al., 1998, Tellus 50B:401-415)
    CSI CSAT3 sonic anemometer
    RM Young 43347 RTD temperature probe (29.6 m)
    Vaisala PTB101B analog barometer
    Vaisala/CSI HMP45C temperature and relative humidity probe (29.6 m)
    Kipp & Zonan CNR1 net radiometer and CSI 100 ohm current shunt module (above canopy)
    CSI model 237 leaf wetness sensor
    Type T thermocouples (soil/tree temperatures; air temperatures from 0.25 to 2 m)
    CSI 10TCRXTCR thermocouple reference thermistor
    REBS HFT-3 soil heat flux plate
    CSI CS615 soil water content reflectometer probes
    LI-COR quantum sensors (PAR)
    RM Young model 03002 wind sentries
    CSI CS500 temperature and relative humidity probes
    REBS Q7.1 net radiometer (above forest floor)
    Texas Electronics 6" tipping bucket rain gauge with CSI CS705 snowfall adapter and Onset Hobo Event Logger
    CSI MD9 multidrop and SC532 interfaces
    NEC Ready 120LT notebook computer and Iomega 250 MB Zip drive
    Kohler 4 kW propane generator (located 0.5 km north of tower)
    Trojan T105 battery bank (12 VDC @ 1100 AHr) recharged with Todd 45 amp battery chargers

Sampling Frequencies:
    0.1 second - eddy covariance measurements (wind speed/direction, CO2, H2O)
    1 second - radiation, air temperature, H2O mixing ratio, barometric pressure
    5 seconds - canopy PAR, net rad, wind speed/dir, air temperature/humidity
    1 minute - incoming direct/diffuse PAR, leaf wetness
    10 minutes - air/soil/tree temperatures, soil moisture, soil heat flux
    21 minutes - interval between profile CO2 measurments for any level

Standards and Calibration:
    CO2 standards - 340, 440, 550 ppm CO2 in air (calibrated using NOAA primary standards).
    CO2 mixing ratio - LI-6251 zeroed every 42 minutes, calibrated with 3 standards every 4 hours.
    CO2 and H2O flux - LI-6262 calibrated with LI-6251 and HMP45C measurements.

VIEW PLOTS (You will need Adobe Acrobat and/or Ghost View to view these plots)


Original page by Bruce Cook. Please send comments or questions to Kelly Cherrey

modified by Kelly Cherrey, May 18, 2007