Data Set Name: Barrow CO2 fluxes 2001 Contact Person: Steven F. Oberbauer Department of Biological Sciences Florida International University Miami, FL 33199 ph: 305-348-2580 email: oberbaue@fiu.edu Source of support: OPP-9907185. The data is part of the U.S. effort of the international tundra experiment (ITEX) and are based on a collaboration between the Michigan State Arctic Ecology Laboratory headed by Patrick Webber. Data set overview: These data represent eight diurnal courses of carbon dioxide fluxes from the Barrow ITEX wet and dry sites in 2001 for control and experimental plots. Data cover June – August 2001. Study site: Barrow wet and dry ITEX sites Purpose: Document treatment effects of ITEX chambers on carbon fluxes and productivity Treatments: ITEX chamber and controls for both wet and dry tundra sites (see http://www.cevl.msu.edu/ael/index.html) Design: 5 plots of each of control, experimental (ITEX chamber) on wet and dry tundra sites Sampling frequency 6 times over the 2001 growing season. Data collection and processing: Diurnal courses of net ecosystem carbon dioxide fluxes were assessed at approximately bi\weekly intervals on the study plots. We used a modification of techniques described by Bartlett et al. [1989], Whiting et al. [1991]. In this procedure, a rapid, transient measurement of ecosystem exchange is made using a portable, cylindrical, acrylic cuvette (0.7 m high, 0.45 m diameter) attached to a polyvinyl chloride chamber base permanently installed in the soil. CO2 concentration changes were measured with a Li-6200 portable photosynthesis system (LI-COR, Inc, Lincoln, Nebraska). For each measurement, three 30 s incubation periods were followed. If the values of the sequential readings differed substantially, the process was repeated until a steady value was obtained. The mean of the last two of the three observations is used for the final value. Six sets of measurements were made over the course of 24 hours (4 hour intervals). An additional set of measurements was made under artificially darkened conditions in early morning (0400 hours) to estimate ecosystem dark respiration and one plot from each treatment (henceforth referred to as a reference plot) was measured for dark respiration at all sampling intervals. To calculate gross ecosystem uptake of non reference plots for sample periods other than 0400 hr, the ratio of the dark respiration of the plot of interest to that of the reference plot for that treatment was used to scale the dark respiration of the reference plot at the desired sample interval. In practice, the dark respiration of the reference plot at the desired sample interval was multiplied by the ratio of the respiration rates of the plot of interest to the reference plot at 0400 hr. The data are saved to a laptop computer as ASCII text and recomputed using RECOMP.EXE to correct for difference in individual chamber volumes (due to depth of base). Level of precision: 0.2 µmol/m2/s Data Format: Microsoft Excel 2000. Computer: Data prepared on Dell Optiplex running Window 98 Data fields Date (integer), Long (integer), Lat (integer), diurnal (integer) , site (alphanumeric), rep (integer), treatment plot (alphanumeric), Net_CO2_exchange (integer), Dark_respiration (integer), Gross_CO2_exchange (integer), PPFD (integer), TAIR (integer), CO2_concentration (integer) Plot numbers refer to Webber Plot numbers. D= dry site, W= wet site. CTL = control plot, OTC = open top chamber = warmed plot. Conditions for use: Permission of contract person is required. Note: Missing data for temperature, PPFD, and CO2 are from a corrupted file. Flux values are recorded in a notebook as back up so flux values were not lost. These data have been carefully checked against notebook for coding errors. If a value was recorded in the notebook but not stored on the LICOR the flux values were taken from the book and corrected for volume. The data for temperature, PPFD, and CO2 are taken from the nearest data point in time. References: Whiting, G. J., J. P. Chanton, D. S. Bartlett, and J. D. Happell, Relationships between CH4 emission, biomass, and CO2 exchange in a subtropical grass-land, J. Geophys. Res., 96, 3067-3071, 1991. Bartlett, D. S., G. J. Whiting, and J. M. Hartman, Use of vegetation indexes to estimate solar radiation and net carbon exchange of a grass canopy, Remote Sens. Environ., 30, 115-128, 1989.