CO2, CH4, and H2O flux data and associated environmental variables for the BBC collapse scar for 2004

This data set contains flux measurements for the transect from the center of the BBC collapse scar (0m) into the surrounding fire scar (30m) of the Survey Line Fire (burned in June-July 2001).
We measured CO2, H2O and CH4 fluxes every one to two weeks throughout the growing season of 2004. We measured fluxes at permanent plots established from the center of the bog into the surrounding burn at 0, 6, 12, 18, 24, and 30 m on the east and west side of the transect. Flux measurements on either side of the transect were treated as replicates. CO2 and H2O fluxes were measured using a Li-840 infrared gas analyzer (Licor Inc., Lincoln, NB, USA). The IRGA was calibrated before each trip to the field using a span of 400 ppm and a zero of N2 gas. We logged data every 0.5 seconds for 2 min. To account for measurement variability, we conducted two measurements in succession at each location, after flushing the chamber for accumulated CO2 and H2O. For the flux measurements, we built plexiglass chambers with pipe insulation bases with dimensions of 61 × 61 × 30.5 cm, 61 × 61 × 61 cm, or 61 × 61 × 122 cm. The shorter chambers were used in the collapse portion of the transect. Chambers included fans for air circulation, inlet and outlet ports for CO2 measurements, or just outlet ports for CH4 measurements (Carroll and Crill 1997). We placed chambers directly on the soil surface and used pipe insulation and plastic sheeting to make a solid seal during the measurement. To estimate the volume for each chamber measurement, we measured the distance to the soil surface from a 6 cm grid suspended 30 cm above each plot, the surface area was then used to calculate the chamber volume for each measurement. Dark measurements were used to determine CO2 derived from soil and root respiration (ecosystem respiration) using a two-layer cloth shroud with a reflective surface to exclude solar radiation. To estimate net ecosystem exchange (NEE) of CO2, we conducted chamber measurements of plant and soil respiration and plant uptake. NEE data are not reported as NEEmax (NEE at PAR > 1000 µmol m-2 s-1) as PAR only once surpassed 1000 µmol m-2 s-1 during field measurement trips in 2004. Smoke from wildfires through July and August reduced PAR and likely influenced relationships between PAR and NEE. After experimenting with different incubation lengths, we conducted 40 min methane flux measurements to compensate for low flux rates and large chambers. Syringe samples were taken after deploying the chamber and at 8 min intervals, yielding 6 gas samples. We analyzed gas samples using a Varian CP-3800 gas chromatograph with a flame ionization detector (Varian Inc., Palo Alto, CA, USA). We calibrated the GC before each use using standard gases (CH4: 99.9 and 1020 ppb; CO2: 284 and 10195 ppm). We calculated CO2, H2O and CH4 flux rates using linear regressions of gas concentrations over time. We excluded all data sets that did not exhibit initial linear fluxes (r2 < 0.9).