Radiometric Reflectance Measurements of Northern Great Plains Rangeland and Crested Wheatgrass Pastures

Abstract

Calculated reflectance factors and vegetation indices derived from radiometric reflectance measurements were used in regression analyses to test for a single relationship between canopy reflectance characteristics and measured vegetation parameters from 1 moderately grazed and 1 heavily grazed native rangeland pastures and 1 crested wheatgrass [Agropyron desertorum (Fisch. ex Link) J.A. Schultes] pasture. The study was located on a Williams loam (fine-loamy mixed, Typic Argiboroll) near Mandan, North Dakota. Reflectance measurements were made near solar noon once a week during the 1983 and 1984 growing seasons. There was a statistically significant relationship (r=0.76**) between leaf area index and dry green matter among pastures and years. However, each pasture exhibited a unique relationship (statistically significant) between vegetation indices developed from the reflectance measurements and leaf area index or dry green matter. Based on the techniques and wavebands used in this study, over a given geographic region and with pasture management practices known, it may be possible to remotely estimate green dry matter.