Dynamics of Tree and Shrub Vegetation in the Eastern Sayan Mountain Tundra

Climate change entails shifts in the ranges of woody plants along both latitudinal and altitudinal gradients in the boreal forest biome. In this study, dendrochronological and GIS technologies have been used to evaluate shifts in the upper distribution limits of trees and shrubs in the Eastern Sayan Mountains. The results show that upward expansion along the altitudinal gradient and increase in projective cover against the background of climate warming reach a maximum in shrubs (Betula spp., Salix spp.); then follow Siberian larch (Larix sibirica Ledeb.), Siberian stone pine (Pinus sibirica Du Tour), and Siberian fir (Abies sibirica Ledeb). The abundance of P. sibirica undergrowth in the mountain forest–tundra ecotone has increased, which is due to a rise in May–August air temperatures (r = 0.97). In zones with sufficient moisture supply (high mountains), warming stimulates radial growth of trees and shrubs and promotes their expansion to the mountain forest–tundra.