Abstract
The upper beech forest line has a very complicated shape in a mountain valley running in the W-E direction. On the shady northern slope it reaches an average of 1659 m above sea level, while on the insolated southern slope, about 1760 m. It was found and proven statistically that the altitude of the boundary is dependent on the relative isolation (r = 0.309, α = 0.01), exposition and relief of the territory.
Keywords
altitudinal vegetation belts; climatic upper beechwood line; inversion of forest belts; exposures; relative insolation; biosphere reserves; Stara Planina Mts.