This is CO2 flux data, NEE and Re, from four locations on the eastern side of the Toolik River where by snow fences were established as part of IPY. We measured CO2 excange during the summer of 2007 multiple times and at 3 locations (3 replicates) with four treatments, control, drift, drift and shoveled and drift, shoveled and watered ( C, D, DS, DSW). The three replicates were called: upper, south, north (U, S, N).

During the snow-free growing season (June-August), ecosystem CO2 fluxes were measured using a clear plexiglass chamber (0.5 x 0.5 x 0.40 cm). Net ecosystem exchange (NEE) and ecosystem respiration (ER) measurements were made at mid-day in tussock and intertussock location. CO2 concentration, temperature and humidity within the chamber were monitored using a LI-6200 portable photosynthesis system (LI-COR Biosciences, Lincoln, NE). The chamber was fitted with two small fans and a sensor to measure photosynthetic photon flux density (PPFD). The chamber was vented to the atmosphere between measurements until [CO2] returned to ambient levels. CO2 exchange rates during the clear and dark chamber measurements were calculated following Hooper et al. (2002). Photosynthesis is presented as a positive flux and respiration as a negative flux in this study. Therefore, gross ecosystem photosynthesis (GEP) was determined by subtracting ER (dark chamber) from NEE (clear chamber).