Soil variables and constants

Variables related to soil gas flux have their own groups in the data dictionary and data files.

The SoilConst group

Constants are computational constants used in the flux calculation. These can be found in the Data Dictionary under the group called SoilConst.

Table 11‑1. Soil gas flux computational constants.
Constant Description
Vcham The volume of the chamber.
Virga Volume of the IRGA.
Area Exposed soil area within a collar.
Offset Height of the chamber base above the soil surface.
Vtotal Total volume.
Ctarget Target concentration for computing fluxes.

The SoilConfig group

These settings can be found in the Data Dictionary under the group called SoilConfig.

Table 11‑2. Soil measurement settings.
Meas Description
Rep duration Time (s) chamber is closed for each repetition.
Dead band Delay (s) after closing to begin computations.
# Reps Number of repetitions per measurement.
Extra Delay (s) after opening before starting next repetition.
ID Tag Identifier, used in the file name.
Soil Type Needed for the Stevens Probe.
Tsoil The source of a soil temperature (Stevens probe, Tleaf, Tleaf2, or none).

The SoilData group

Real-time data during a measurement is available in the group called SoilData. Some of these are shown in the Measure Flux window.

Table 11‑3. Soil data from the group called SoilData.
Label Description
TIME The time_t value of the data record.
CStatus Status of chamber ("Open", "Closing", "Closed", "Opening").
MStatus Status of the measurement ("Idle", "Closing", "Dead band", "Sampling", "Opening", "Waiting").
MStatusN Numeric status of the measurement (0 = "Idle", 1 = "Closing", 2 = "Dead band", 3 = "Sampling", 4 = "Opening",
Rep Current repetition and total. e.g., 3/4.
Elapsed During measurement, elapsed time since chamber closed.
Progress Percent of the measurement completed.
RepProg Percent of the current rep that is completed.
CO2 Value comes from CO2_s in group Meas.
H2O Value comes from H2O_s in group Meas.
Cdry Dry CO2. Value comes from CO2_s_d in group Meas2.
Tsoil Soil temp. Source depends on setting of Tsoil in SoilConfig.
Msoil Soil moisture, (measured by Stevens Probe).
Tair_sc Air temperature within the soil chamber.
Pressure Value comes from Pa in group Meas.
RH Computed RH in the soil chamber.
dCdry/dt Rate of change of Cdry over previous 2 seconds
F-to An estimate of what the final flux will be at time to

The SoilComp2 group

When a rep is finished, a SoilComp2 record is published.

Table 11‑4. SoilComp2 record published at the end of a repetition.
Label Description
MeasNum Measurement number.
RepNum Repetition number.
F_target Flux computed Cdry = C_target.
F_to Flux computed at Cdry = C_o.
Cdry_to Cdry concentration at chamber close.
P_to Pressure at chamber close.
T_to Chamber air temp at chamber close.
W_to Chamber water mole fraction at chamber close.
slope Slope of dCdry/dt as function of Cdry.
intercept Intercept of dCdry/dt as function of Cdry.
Ts_avg Average soil temperature over the rep
Ms_avg Average soil moisture over the rep