The Boreal Limits of Conifers

T HE expressions "forest-limit", "timber-line", or "tree-line" are all some- what vague and difficult to define, and for the same reason it is not always easy to plot them accurately on a map. In the sense employed by North American writers, "timber-line'' may mean the limit of commercially profitable forest utilization, the limit of forest in a biological sense, or simply the limit of trees. Sometimes it is not even easy to determine "when a tree is a tree".