Applications of Solar Induced Fluorescence to the Assessment of Vegetation Photosynthetic Function and Physiological Condition
P. K. E. Campbell*1, E. M. Middleton2, W. B. Cook3, J. McMurtrey III4, L. A. Corp5 and L. M. Butcher5
One of the most important issues facing scientists today focuses on balancing the global carbon cycle and determining the major carbon (C) sources and sinks within the Earth system. Current remote sensing methods do not provide accurate estimates of vegetation physiological status and C sequestration potential. Actively induced fluorescence measurements are commonly used in plant physiology to assess the condition and carbon allocation efficiency of leaves and whole plants, especially techniques based on actively induced chlorophyll fluorescence (ChlF). In the terrestrial biome, direct measurement of the solar-induced vegetation ChlF have not been possible due to the strong reflectance signal in the red and near-infrared spectral region. The possibility of using an ultra-high spectral resolution instrument, a Fraunhofer Line Discriminator (FLD), to measure the solar induced ChlF signal, as it "fills in" the atmospheric Fraunhofer lines in the solar spectrum, has emerged as an attractive approach. If scientifically proven, the FLD approach would allow the direct monitoring of vegetation photosynthetic function, physiological status and C sequestration potential, possibly on a global scale. The goal of the proposed investigation is to determine if solar induced ChlF can provide results, regarding photosynthetic function, similar to those achieved using actively induced ChlF methods at ground level. Both active and passive ChlF techniques will be tested in side-by-side measurements, conducting experiments using manipulated plants, and outdoors on forest and crop canopies.
