In nature, division lines are delineated where multiple important environmental features change. These division lines may be singled out at the intersection of two geosystems (Balon 2000) where the functional uniformity of the geosystems located on both sides are preserved (Forman & Gordon 1986; Cadenasso et al. 2003). A significant environmental boundary is the upper forest boundary (timberline), which separates different vegetation zones: (1) forest from non-forest (Piękoś-Mirkowa & Mirek 1996); climatic zones (2) cool from very cool (Hess 1965); geoecological zones (3) periglacial from temperate forest system (Kotarba 1996). A timberline is a sensitive ecosystem therefore is a good indicator of changes occurring in the environment. There are, however, multiple elements which affect the timberline. This ecotone has also been widely analysed in local, regional, and even monographic studies of numerous massifs. It is necessary to present and organise the great amount of information in order to aid research on the timberline in the Carpathians.