Soil CO2 concentration (DP1.00095.001)

When possible the plots were arranged in a transect with the first plot approximately 15-40 m from the tower in the expected dominant airshed. The middle of airshed was used as the transect vector and plot spacing was based on the distance required for surface soil temperature and moisture measurements to be spatially independent at the 1 hectare scale during site characterization (capped at approximately 40 m due to logistical constraints). Soil plots were microsited as necessary to avoid obstacles (e.g., boulders, streams, and paths) and more compact plot layouts were used at small sites. The CO2 concentration of soil air is measured at three depths within each plot, starting at approximately 2 cm. The depths of the two deeper sensors vary among sites and were chosen based on megapit soil horizon data (NEON.DP1.00097), expected soil CO2 concentration, and ecosystem type (see NEON.DOC.003146). Instrumentation: Vaisala - GMP343