This guide has been developed to provide insight in applying ecological information to classify and map forest land in mid-boreal Saskatchewan. It begins with an overview of the province's ecological classification system and a review of the five types of information sources of ecological information. It then describes the four steps used to determine the ecosite phase level of a site from aerial photographs and associated sources. Section 5 contains keys to identifying the ecosite phase through the interpretation of resource information. Section 6 provides five examples of typical toposequences found in mid-boreal regions of Saskatchewan. Each example includes an aerial photo stereogram of the selected area, an example transect, a forest inventory and soil survey maps of the area, and interpreted landscape profile and summary tables. The final sections include references and a glossary. Appendices include lists of ecological units and soil types, information on the ecology & identification of tree species, and soil classification information.