Comparing biophysical properties of the Streletskaya Steppe Reserve and the Konza Prairie

Reflected radiation by a crop canopy can be influenced by changes in the biological processes and physical attributes of the canopy. The study was conducted to characterize the effective leaf area index (LAI) and leaf angle distribution of the Streletskaya Steppe Reserve of the Russian Republic and the Konza Prairie in Kansas and to determine dependence of leaf optical properties on leaf water potentials of some dominant species in discrete wavebands in the visible and near-infrared (NIR) (spanning 400-1000 nm range). Biophysical properties were measured in July 1991 during the Kursk Experiment (KUREX-91) and in the summer of 1989 during the First ISLSCP Field Experiment (FIFE-89). Leaf area index, leaf angle distribution, mean tilt angle, canopy height, leaf optical properties, and leaf water potential were measured. Generally, the KUREX-91 steppe sites were characterized by high leaf area index and an uniform leaf angle distribution, while the FIFE-89 prairie sites were characterized by low leaf area index and an erectophile canopy. There were differences in leaf reflectances between plant groups (grass versus forb) and between plant communities (prairie versus steppe), but not generally for transmittance. Leaf optical properties (visible and NIR) were not related to leaf water potential (over the -0.5 to -3.5 MPa range) for dominant plant species observed at the KUREX-91 and FIFE-89 sites. Characterization of the biophysical properties during the FIFE-89 and KUREX-91 experiments provide information useful in understanding the differences in canopy bidirectional reflectance observed at the two grasslands.