Studies on the Relationships among the Leaf Transfer Coefficient for Water Vapor, Soil Water Content, and Spectral Reflectance

Abstract

The relationship between the soil moisture content and the leaf transfer coefficient for water vapor c_e was examined. The correlation between these variables are represented by the soil moisture content at the wilting point, and a numerical parameter that changes with vegetation type and soil type. The present c_e model that considers these soil parameters was examined, with a simulation of the heat balance over a sorghum field conducted using the canopy model and routine meteorological data. The calculated results agree well with observed values. The relationship between the spectral reflectance and c_e was also examined. The value of c_e decreases with decreasing the reflectance ratio (r1220 nm/rl550 nm) and vegetation vigor index (VVI). The VVI is a useful index to obtain information concerning the vegetation vigor when the soil moisture content is not known.