Detection and Measurement of Water Stress in Vegetation Using Visible Spectrum Reflectance - Art Zygielbaum

• Dissertation Defense
• 12/2/2009

At any scale, from a single microbe to the planet that nurtures us, water defines our place in the universe. It provides the hydraulic forces needed to give plants structure, and the medium enabling photosynthesis, the basis for most life on earth, to occur. Knowledge about the water status of plants is vital to understanding the state or condition of vegetation, which is important to scientists in disciplines as diverse as agriculture, geography, and climatology. Non-destructive and remote sensing of plant water status allows the gathering of such information across wide geographic extents and over long periods of time. During this seminar, the results of extensive greenhouse research on corn and soy plants undergoing water deficit will be presented. The effort resulted in the identification of a previously unknown systematic increase in visible light reflectance as plants become increasingly water stressed. The effect is more pronounced in corn than in soy. Because water molecules do not absorb light in the visible spectral range, this finding offers new insights into the physical and chemical processes which protect plants from damage due to water stress. The finding also suggests a potential for using only visible light to detect and measure plant water status non-destructively, and perhaps even by means of sensors on remote platforms.

Satellite-based Esitmation of Chlorophyll-a Concentration in Turbid Productive Waters - Wesley Moses

• Dissertation Defense
• 10/8/2009

Inland, coastal, and estuarine waters, which are often turbid and productive, play a crucial role in maintaining global bio-diversity and are of immense value to aquatic life as well as human-beings. Concentration of chlorophyll-a is a key indicator of the trophic status of these waters, which should be regularly monitored to ensure that their ecological balance is not disturbed. Remote Sensing is a powerful tool for this.

Reflectance models that are based on the red and near-infrared spectral channels of MODIS and MERIS satellites have been developed for estimating chlorophyll-a concentration. The results obtained from data collected by field spectrometers, airborne sensors, and space-borne sensors over inland, estuarine, and coastal waters from various geographic regions, with widely varying biophysical characteristics, show that the developed models have a very close and stable relationship with chlorophyll-a concentration, thereby precluding the need for re-parameterization of the models for each water body. Chlorophyll-a algorithms have been developed and calibrated, which have the potential for universal application to estimate chlorophyll-a concentration from satellite data routinely acquired over turbid and productive waters from around the globe.