Leaf-to-aircraft measurements of net CO2 exchange in a sagebrush steppe ecosystem

Abstract

Measurements of net CO2 flux density (μmol m-2 s-1) from a high elevation, sagebrush steppe community in southeastern Wyoming (USA) were compared quantitatively among four different instrument systems (leaf cuvette and 1 m2 community chamber for gas exchange measurements; tower and aircraft eddy covariance systems) by minimizing spatial and temporal variability. Ground-based flux measurements were recorded at an intensive site located near the midpoint and directly beneath an approximate 20-km flight transect. A high degree of homogeneity in plant species composition, density, cover, and the amount of leaf area per unit ground area, as well as little topographic variability, was measured at the intensive site and along the flight transect. Flux measurements were compared on days with relatively high and low soil moisture availability (predawn plant water potentials >-0.8 MPa and