Secondary forests are those that have replaced primary ones as a result of various human impacts. In the west of the Russian boreal zone (Murmansk and Leningrad Regions,Republic of Karelia and adjacent parts of the Arkhangelsk and Vologda Regions), they predominate in most of the territory. Secondary forests (SF) have formed in the past and continue forming upon: 1) extensive clear cutting (practiced widely from the 1930’s until the 1960’s); 2) wide- and narrow-strip clear cutting (currently practiced method); 3) partial cutting, mainly selective cutting of various removal rates, including ongoing cutting
(practiced over the past 3–4 centuries); 4) slash burning in forest land (practiced widely for several centuries late into the 19th c.); 5) anthropogenic forest fires; 6) transfer of forest land for permanent agricultural crops and their abandonment afterwards; 7) forest drainage (implemented on a large scope in the 1960’s-80’s and terminated entirely by the mid-1990’s), etc. This paper is based on nearly 40 years of experience in the study of forests through the full range of stages of spontaneous (in primary forests) and anthropogenic successions. Surveys covered almost all types of geographical landscapes distinguished for Karelia and adjacent areas. The focus is on the summary of the research methodology. The concepts and definitions applied to SF are critically analyzed. The diversity of possible SF origins and generations is demonstrated. The set of methods for SF identification is analyzed. Three major categories of methods are distinguished: 1) remote sensing; 2) analysis of archival and contemporary statistical data; 3) in situ surveys. They are arranged in the order of application to an ‘unstudied’ area. Practically all these categories of methods are used in various sequences, extents and ratios, depending on the task, size of the study area, required level of detail, and previously available experimental background. Their efficiency and sufficiency for identification of the genesis, structure and dynamics of SF were evaluated. It is argued that a most complete and reliable identification of such forests is possible only with the application of the entire set of the methods and approaches described.