Response of thematic mapper bands to plant water stress

Abstract

Changes in leaf reflectance as water content decreases have been hypothesized to occur in the 1 55-1.75 and 2.08-2.35 μm wavelength regions. To evaluate this hypothesis, studies were conducted on ryegrass (Lolium muitiflorum Lam.) and oats (Avena saliva L.), which were grown in a controlled, outdoor situation. Both fully-watered control beds and water-stressed beds were periodically examined with a spectroradiometer calibrated against a reflectance reference of polytetrafluoroethylene. The observed changes correspond to those predicted by stochastic leaf models employed by other investigators (leaf reflection increases in the l.55-l.75μm region as leaf water content decreases). Although the percentage changes in TM bands 1-3 are nearly as great as those found in TM bands 5 and 7, the absolute values of reflectance change are much lower. We believe that these patterns are probably characteristic of a broad range of vegetation types. In terms of phenomena detection, these patterns should be considered in any practical remote sensing sensor scenario.