Relating Plant Carbon Exchange with Reflectance Spectroscopy

One important aspect of climate change research is to monitor and model ecosystem carbon dynamics. Spectral reflectance data from satellites, aircraft, and in situ measurements have shown capabilities to track exchanges of carbon, water and energy between terrestrial ecosystems and the atmosphere. A key element of this study is to relate spectral characteristics of leaves, measured at high-spectral resolution, to their biological activity such as photosynthetic rate (calculated from CO2 exchange). In this research, the biological activity and spectral reflectance of leaves were monitored over the course of a full diurnal cycle using simultaneous gas-exchange and high spectral resolution measurements. An experimental model based on step-wise linear regression was created (adjusted R-square value 0.984) by applying statistical tools to study the relationship between plant photosynthesis and spectral reflectance indices. Indices which were shown to be statistically significant to photosynthesis, such as PSRI, PRI, EVI, WBI, etc., demonstrate the various biochemical parameters that may contribute to changes in the photosynthetic activity over the diurnal cycle. This carbon exchange/reflectance model, created using in situ techniques, can then be applied to crop-level canopy reflectance acquired via high-spectral resolution instruments from aircraft and satellite.