Changes in the composition, structure, and altitudinal distribution of low forests at the upper limit of their growth in the Northern Ural Mountains

Changes in the composition, structure, and altitudinal distribution of low forests at the upper limit of their growth over the past 50 years have been studied in the Tylaisko-Konzhakovsko-Serebryanskii Massif (the Northern Urals). The qualitative and quantitative assessment of these changes has been made on the basis of descriptions, photographs, and maps made in 1956 and 2005. The results show that the upper boundary of low forests on the majority of slopes has ascended. Considerable changes have occurred in the composition, density, and height of the tree layer in the communities that formed the upper low-forest boundary in 1956. Among a fairly large number of tree species growing in the subgoltzy belt (Picea obovata, Larix sibirica, Pinus sibirica, and Abies sibirica), the birch Betula tortuosa has expanded most actively, whereas the proportions of P. obovata and especially L. sibirica in low forests have decreased. These changes are explained by climate warming and increasing humidity.