Influence of Water Content on Spectral Reflectance of Leaves in the 3–15- $\mu\hbox{m}$ Domain

This letter describes a laboratory experiment where reflectance signatures of three plant species are measured at a leaf level in the 3-15-μm spectral domain. The leaf samples are progressively dried in order to analyze the behavior of their spectral signature according to the variations in their water content. Our first objective aims to underline leaf water content (LWC) impact on the spectral signatures. This work is a necessary step toward further studies dealing with interpretation of multispectral remote sensing data or estimation of water stress and energy budget. The drying process and measurement method are detailed. This letter deals with dry and fresh leaves (as found in literature) and considers intermediate water content levels as well. For intermediate LWC levels, our analysis outlines some important results: The spectral domain may be divided into two parts, namely, 3-5.5 and 5.5-15 μm, each corresponding to different impacts of LWC variation; both sides of a cherry tree leaf have not the same behavior according to the water content amount; and, in the 8-15-μm, the drying process impacts when the LWC becomes lower than a threshold value (around 30%).