AIRBORNE SYNTHETIC-APERTURE RADAR ANALYSIS OF RANGE-LAND REVEGETATIONOF A MIXED PRAIRIE

Microwave radar is a potentially useful tool for monitoring the condit ion of the rangeland. A study was conducted in a mixed prairie communi ty at the Agriculture Canada Research Substation at Onefour, Alberta i n 1991 to examine the effects of historical management on synthetic ap erture radar (SAR) data obtained from 2 aircraft flights, 24 May 1991 and 1 August 1991. Ground-truthing expeditions were conducted on the s ame days to obtain estimates of vegetation amounts, species distributi on and soil moisture. A former grazing experiment established in 1955 and abandoned 20 years ago enabled comparison of 3 grazing treatments, continuous, rotation and free choice superimposed on native range, cr ested wheatgrass (Agropyron cristatum (L.) Gaertn.) and Russian wildry e (Elymus junceus Fish.). The ground data and imagery were integrated in a Geographic Resource Analysis Support System (GRASS). Fields that had been cultivated and seeded to Russian wildrye had higher radar bac kscatter than native range. The radar backscatter from crested wheatgr ass fields was similar to native range in May but higher than native r ange in August. Radar backscatter was positively correlated with numbe r of years since seeding with Russian wildrye. Generally there was lit tle difference in radar backscatter with grazing treatment. Correlatio n analyses between radar digital number extracted from the ground trut h sites and vegetation and soil parameters revealed, depending upon sw ath mode, significant relationships between radar backscatter and the amount of certain grass species, radar backscatter and canopy moisture , and radar backscatter and soil moisture in May. A significant negati ve correlation was observed between radar backscatter from the August images, in both swath motles, and percent ground cover. The results of this study indicated a role for SAR imagery in evaluating range chara cteristics.