CO₂ Flux over Arid Ecosystem in Western Australia

Abstract

The methodologies and results of CO₂ fluxes measured on an arid land of Sturt Meadows in Western Australia are described here. There, we selected two measurement places .One was a small forest of Eucalyptus trees (14 meters height as average) and the other was an afforestation trial site where trees were sparsely planted. The CO₂ fluxes were measured by a stationary measurement method with a tower and also an airborne measurement method with a small aircraft. Both methods employed an eddy covariance technique. The CO₂ uptake rates by the small forest on a clear mid-day were 12-17 µmol/(m²·s) from the stationary tower measurement when the soil water content was high. These values agreed well with those obtained from the airborne measurement. The CO₂ uptake rate, however, decreased with decrease in the soil water content even though the solar radiation increased. The soil water content has a great influence on the CO₂ uptake rate in the arid region, and the dependence of the CO₂ flux on the solar radiation depends on the soil water content. The measurement results on the sparse forest also indicated that both measurement methods estimated similar values of CO₂ flux. These results suggest that the airborne method developed can be an efficient method to quantify CO₂ fluxes over various vegetation areas in the heterogeneous arid region, where a measurement tower is hardly built. However, a sophisticated foot-printing analysis is needed to specify the source region of the CO₂ flux.