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Abstract
Ground reflectance measurements, aerial video, and SPOT satellite data were compared for assessing herbaceous phytomass production and cover measurements on a south Texas rangeland area. Aerial video and ground reflectance data were acquired in April 1990 and in May and October 1991. For the October date, SPOT data was also obtained. Vegetation vigor was generally low in April 1990 due to insufficient precipitation and past drought, whereas more vigorous growing conditions prevailed in May and October 1991. The near‐infrared(NIR)/red ratio and normalized difference vegetation index (NDVI) were computed from the respective reflectance, video, and SPOT data. Regression analysis was used to relate the remote sensing data to phytomass and cover. Neither video or reflectance data were related to phytomass in April 1990, but they were significantly (p = 0.01) related to cover. In May and October 1991, video and reflectance data were significantly (p = 0.01) related to both phytomass and cover. SPOT data was also related to phytomass and cover in October. The better relationships of the remote sensing data to the biophysical variables in May and October 1991 was primarily attributed to the more vigorous growing conditions on these dates. These results showed that reflectance, aerial video, and SPOT satellite indices data may have potential for assessing phytomass production and foliar cover on rangelands.
