Carbon Flux Measurements and Results






Eddy covariance

Following Ameriflux standard

Few km2, 1 replicate per site

Continuous (20 hz), 30 min averages

Soil CO2 flux

It is measured in two ways:

1) by monitoring surface CO2 fluxes regularly with a static chamber and Li-Cor 6400-09 gas exchange system and

2) by using buried CO2 sensors (model GT222, Vaisala, Helsinki, Finland) to monitor continuously the soil depth concentration gradient of CO2 (Tang et al. 2003).

30 cm diameter, 9 replicates per site 10 cm diameter, 3 depth (2, 10, 20 cm), x 3 plots, 27 sensor per site.

1 month interval, more frequent during growing season Continuous (1 s), 30 min averages

Soil CH4 flux

We use the static chamber approach for measuring rates of CH4 consumption by soils in the three treated sites (Holland et al. 1999).

30 cm diameter, 20 chamber bases located systematically per site

1 month interval, more frequent during growing season


NPP is estimated by summing annual estimates of litterfall, aboveground tree production, fine root production, and coarse root production.

3 plots 25 m diameter per site


Eddy covariance

The eddy covariance system uses two, fiber composite, light weight, 28 m towers in the forests sites, and a 4 m pole in the fire site. The equipment used (see Table below) is the same for the 3 sites. We use a closed path analyzer, a 4 mm 4 m long tubing (9 in the fire site) and a flow rate of 10 l min-1.

The software (Giovanni Manca, CEALP, Italy), apply linear detrending, coordinates rotation and corrections for flux losses. we flag carbon flux, H and LE for quality, considering: rain, variances of CO2, H2O, spikes and follows the proposed Ameriflux and already implemented CarboEurope criteria of Foken (Steady state test and Integral turbulence characteristic test,







CSAT3 Campbell

CO2 and H2O

li-7000 licor

- total
- diffuse
- sunshine

BF3 deltaT

Par reflected

Li190 Licor

Fine wire thermocouple

FW05 Campbell


5.4103.20.041 Thies clima

- Precipitation
- Air temperature Air humidity
- Wind speed & directions
- Hail and rain intensity and duration.

WXT510 Vaisala

Short/long-wave incoming/ outgoing and Net Radiation

CNR1 Kipp & Zonen


TR525 USW Texas inst.




Soil temp profile
(2, 10, 20, 45 cm)

107 Campbell

Soil water content profile
(2, 10, 20, 45 cm)

ECH2O-EC20 Decagon

Soil water content profile
(2, 10, 20, 30, 70-100 cm) second profile since March 2006

CS616 Campbell

Soil heat flux

HFP01SC Hukseflux, Rebs




Tubing diameter and length

4 mm 9 m (F)
4 mm 4 m (C and R)

Air flow

9.5 l min-1

Canopy and instrument height

4 m until Feb 2007, then 2.5 m (F)
18 m, 23 m (C and R)

Profile system

CO2, H2O (LI-840, Licor) and temperature sampled at 1, 8, and 16 m (C and R only)


Litterfall is been collected quarterly from 15 circular litterfall traps (60 cm in diameter) per subplot. Prior to the first NEE measurement year, we tagged and measured the DBH of all trees within the subplots. At the end of second growing season of NEE measurements (late fall), we will measure the DBH of all trees again, and will extract two short increment cores. Annual radial growth increments will be averaged per tree, doubled, and added to the measured initial (year 0) DBH to calculate DBH values for subsequent years. Annual changes in DBH will be combined with local allometric equations to estimate annual growth in stem wood and bark, branch wood and bark, and foliage.

Soil CO2 and CH4

CO2 diffusion probe technique:

Small solid-state infra-red gas analyzers (GMM 220, Vaisala Inc., Finland) were buried at three depths in the soil profile and measured CO2 concentration at ½ hour intervals every day

Soil volumetric water content and temperature were measured with Decagon ECH2O probes and thermocouples, respectively

Using a model of soil diffusivity including soil water content and temperature (Moldrup et al.,1999) the rate of CO2 diffusion between the different depths was used to calculate CO2 flux at the soil surface

CO2 and CH4 Static-chamber technique:

  • 30-cm diameter PVC rings were permanently placed in the soil, distributed at 15 locations around each study site
  • Samples of gas headspace were taken at regular intervals
  • Gas samples were analyzed for CO2 and CH4 using gas chromatography. Changes in concentration over time were used to calculate fluxes



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