We deployed three eddy covariance towers along a burn severity gradient (i.e. severely-, moderately-, and un-burned tundra) to monitor post fire Net Ecosystem Exchange of CO2 (NEE) within the large 2007 Anaktuvuk River fire scar during the summer of 2008. This data represents the post fire energy and mass exchange at the unburned site for 2013-2019.
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We deployed three eddy covariance towers with identical instrumentation across a burn severity gradient (Rocha and Shaver 2009). The three sites (i.e. Severe burn, Moderate burn, and Unburned) were 40 km to the west of the nearest road and were selected during a helicopter survey of the southern area of the Anaktuvuk River Fire scar in late May 2008 (Figure 1; Table 1). Because the fire had burned through September of the previous year, initial deployment of flux towers occurred prior to any significant vegetative regrowth, and our sampling campaign captured the full 2008 growing season (June 1-August 28). Each site was equipped with a Campbell Scientific® CR5000 datalogger that recorded data from micrometeorological instrumentation located on a stainless steel tripod (CM110; Campbell Scientific; Logan Utah, USA) at a height of 2.6 m. Data were stored on a 2 Gb PCMCIA card and downloaded every two to three weeks. Power for the datalogger and instrumentation was located 15 m to the east or west of the tower and consisted of a south-facing solar panel and two 12 V 80 amp-hour batteries enclosed in a polyethylene box. Towers ran continuously through the summer of 2008 with the exception of the severe burn site, which was damaged by a bear during the last week of August. The towers have been in operation since June 2008.
Environmental data were recorded as half hour averages. Net radiation was monitored with a NRLITE net radiometer (Campbell Scientific; Logan Utah, USA). Incoming and reflected solar and longwave radiation were measured with a CNR-1 Radiometer (Campbell Scientific; Logan Utah, USA), while incoming and reflected Photosynthetically Active Radiation (PAR) were measured with a silicon quantum sensor (LI-COR; Lincoln, NE, USA). Air temperature and relative humidity was measured with an HMP45C-L sensor (Campbell Scientific; Logan Utah, USA) enclosed in a naturally aspirated radiation shield, while precipitation was measured with a tipping bucket rain gauge (TE525; Campbell Scientific; Logan Utah, USA). Volumetric water content at a depth of 2.5 cm was measured with two reflectometers (CS616; Campbell Scientfic; Logan Utah, USA), soil temperature at a depth of 2 and 6 cm was measured with two averaging soil thermocouples (TCAV-L; Campbell Scientific; Logan, Utah, USA), and soil heat flux at a depth of 8 cm was measured with four soil heat flux plates (HFP01; Campbell Scientific; Logan, Utah, USA). Measurements of the soil environment were recorded on separate CR1000 dataloggers at the severely and moderately burned sites.
Turbulent fluxes of momentum, sensible heat, latent heat and CO2 were determined by the eddy covariance technique (Baldocchi et al. 1988). Half hourly CO2 and H2O fluxes were calculated as the covariance between the turbulent departures from the mean of the 10 Hz vertical wind speed measured with a 3D sonic anemometer (CSAT3; Campbell Scientific; Logan, Utah, USA) and the CO2 and H2O mixing ratio measured with an open path InfraRed Gas Analyzer (IRGA; LI7500; LI-COR; Lincoln, NE, USA). Fluxes were processed using EdiRe software (University of Edinburgh; Moncrieff et al. 1997) and reported using the meteorological sign convention where negative NEE indicates carbon uptake and positive NEE indicates carbon loss from the ecosystem. Ten Hz data were despiked, rotated to the mean wind streamlines, and corrected for the density effect due to sensible heat transfer (i.e. WPL correction; Webb et al. 1980). Turbulent fluxes of sensible and latent heat captured 78 to 80% of the available energy at each of the sites, which is consistent with energy budget closure observed for other eddy covariance studies (Wilson et al. 2002).
The unburned site consists of a tussock tundra vegetation community with 40% of the ground covered with Sphagnum and feather mosses, and the remaining ground cover was composed of Tussocks, Cloudberry, Labrador Tea, Cranberry and dwarf birch [Betula nana L.].
Rocha, A.V. and G.R. Shaver (2009) Advantages of a two band EVI derived from solar and photosynthetically active radiation fluxes. Agricultural and Forest Meteorology. 149:1560-1563, doi:10.1016/j.agrformet.2009.03.016.
Rocha, A.V. and G.R. Shaver (2011) Burn severity influences post-fire CO2 exchange in arctic tundra. Ecological Applications. 21:477-489.
Rocha, A.V. and G.R. Shaver (2011) Postfire energy exchange in arctic tundra: the importance and climatic implications of burn severity. Global Change Biology. doi:10.1111/j.1365-2486.2011.02441.x.
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