COMPLEMENTARITY OF RADAR AND VISIBLE-INFRARED SENSORS IN ASSESSING RANGELAND CONDITION

Ground Investigations of rangeland use and condition are restricted by resource and travel limitations. Management of these vast, multiuser resources could be enhanced by information from remote sensing. Microw ave radar imagery is becoming readily available and its all weather ca pability provides greater reliability than visible-infrared (VIR) sens ors. The objective of this study was to evaluate a combination of rada r and visible-infrared sensors as tools in rangeland monitoring. Data from Landsat Thematic Mapper (TM) and SPOT VIR sensors were compared w ith data from airborne and ERS-1 synthetic aperture radar (SAR) sensor s to determine similarities and contrasts with a view to exploiting an y synergism. The study site was the Agriculture and Agri-Food Canada O ne four Research Substation in southeastern Alberta. The TM and SPOT V IR sensor bands were highly correlated. The radar sensors were correla ted with each other to a lesser degree. Correlations between VIR and r adar were not high. Vegetation type influenced VIR reflectance and rad ar backscatter. Russian wildrye pastures had high radar backscatter as well as high VIR reflectance. Native range had low VIR reflectance an d low radar backscatter. Crested wheatgrass pastures had low VIR refle ctance and high radar backscatter. Other features, such as exposed sed imentary Cretaceous softrock, had high values for both sensor groups, while intermittent water bodies or shallow depressions characterized b y high clay content and strong microtopography had high radar backscat ter but low VIR reflectance. More information can be obtained from the combination of both types of sensor than from either alone.