Measurements
The Sites
Control Site
Restoration Site
Wildfire Site
Site Characteristics
Measurements
Results
| MEASUREMENTS | SPATIAL SCALE | TEMPORAL SCALE | |
| 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 |
| Productivity | 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 | yearly |
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, http://www.bitoek.uni-bayreuth.de/qaqc/en/forschung/21826/QC_Spoleto.php)
EQUIPMENT
| INSTRUMENTS | |
| AIR | |
| Wind | CSAT3 Campbell |
| CO2 and H2O | li-7000 licor |
| PAR - total - diffuse - sunshine |
BF3 deltaT |
| Par reflected | Li190 Licor |
| Fine wire thermocouple | FW05 Campbell |
| Precipitation | 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 |
| Precipitation | TR525 USW Texas inst. |
| SOIL | |
| 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 |
CS616 Campbell |
| Soil heat flux | HFP01SC Hukseflux, Rebs |
| EDDY SYSTEM | |
| 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 | <0.5m 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) |
NPP
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
Last Updated ( Thursday, 10 July 2008 )