Spatial representativeness of eddy covariance measurements using footprint analysis in arid areas

Based on data measured by eddy covariance (EC) and the Kormann and Meixner model, footprints of the flux of desert shrub ecosystems were analyzed. The contributions of different land types during the growing season in Fukang station in 2007 were estimated. Spatial distributions of footprint source areas were evaluated to reveal the relative flux contribution to the total flux over the entire observation period. The results indicate that: (1) The applied footprint model provides accurate footprint estimates and the flux data can be used for the shrub flux estimations. The flux contribution from shrub land showed that the observed flux data were able to represent seasonal change in the flux of desert shrub ecosystems. The flux contribution rate of shrub was highest during May to July between 10:00 and 18:00 h. (2) The location of the EC system in Fukang is appropriate for monitoring shrub flux. (3) Footprint analysis is necessary because it assesses the contribution of the target land-use type to the total flux for any user-defined period. The flux contribution rate was affected significantly by wind direction and the source region.