Soils of the AOSERP study area are being mapped using the ecological or biophysical approach to land classification. The basic land unit being mapped is the land system which is an area of land through which there is a recurring pattern of landforms, soils, vegetation chronosequences, and water bodies. Using 1:50,000 air photos, the land systems are separated at a reconnaissance level of detail. The emphasis in this inventory is on soils and the landforms on which they occur; both are indicated on maps. Vegetation is not indicated on maps and is handled in terms of general soil-drainage-vegetation relationships. Air photo interpretation and field checking have been completed in all of the AOSERP high priority area to Township 100. Land system maps have been prepared for 1:50,000 NTS sheets 740/11, 12, 13, and 14 and 74E/3 and 4; these accompany this report. Maps of the remaining NTS sheets within the high priority area are in preparation. Soils information from the high priority area above Township 100 has been collected, but maps cannot be made until air photos for this region become available. The dominant upland soils of the AOSERP study area are Gray Luvisols, formed on medium to very fine textured glacial till and glaciolacustrine deposits, and Eutric Brunisols, formed on coarse textured glaciofluvial deposits. White spruce, trembling aspen, and jack pine are dominant cover species on these soils. Soils developed on materials of recent deposition, mainly alluvium, are Regosols and Gleysols. Soils of low-lying, poorly drained areas are mainly Organic. These soils, a combination of bog and fen peats, occupy a considerable portion of the AOSERP study area, but are mainly relatively thin (