|Pinter Jr, Paul
Submitted to: The Earth's Changing Land Global Change and Terrestrial Ecosystems and Land
Publication Type: Abstract Only
Publication Acceptance Date: 5/26/1998
Publication Date: N/A
Technical Abstract: The direct effects of CO2 on reflectance and emittance of plants have not been adequately studied. This information is needed to parameterize canopy reflectance models and to better understand the surface energy balance. Spring wheat (Triticum aestivum L.) was grown for 4 years in an open-field, production environment at Maricopa, AZ, using Free-Air CO2 Enrichment (FACE). Treatments provided exposure to ambient and elevated CO2 (+200 ppm). Main treatment plots were split to test the interactive effects of water or nutrient stress with CO2. Treatments were replicated 4 times. Optical attributes of plants were measured at frequent intervals during the experiments using wideband radiometers, and spectroradiometers. Hyperspectral characteristics of leaves, stems, and heads obtained with integrating sphere were compared with reflectance factors measured at the whole canopy level. Thermal properties were sensed with radiometers and a thermal scanner. Radiation use efficiencies were calculated using a relationship between a multispectral index (NDVI) and the fractional amount of photsynthetically active radiation absorbed by the canopy. Significant differences were found between hyperspectral data from plants exposed to different water and nitrogen treatments. Plants exposed to elevated CO2 displayed temperatures that were consistently warmer than ambient CO2 controls. Effects of elevated CO2 in the optical wavelengths did not vary consistently with CO2 treatment. Observed changes in canopy reflectance factors were attributed to early and mid-season increases in photosynthetically active biomass caused by higher CO2. Non-invasive, remotely-sensed techniques were found to be very valuable tools for monitoring plant response to environmental factors.