The Vegetation of the Subalpine–Taiga Complex and Gold Accumulation by Larch Forests of Eastern Sayan

Abstract

This article summarizes the material from geobotanical and biogeochemical studies into the vegetation of the Irkut River valley in the spurs of the Kitoi Goletzes of the Eastern Sayan Mountains. An analysis is made of the features in spatial structure and the floristic and phytocenotic diversity of vegetation of cryo-steppe open woodland, taiga larch forests and meadow-bog complexes in the high-mountain valley of the Irkut River. It was found that the landscapes of the subalpine cold forest–steppe represented by a combination of sparse herbaceous (ptylagrostis-cobresia, fescue) larch forests, shrub groups with the involvement of Spiraea alpina, Betula rotundifolia, and Dasiphora fruticosa, and communities of cryophytic steppes typically occur at altitudes of 2000 m above sea level. The latter constitute the original element of the forest–steppe, which is often dominated by the endemic fescue Festuca komaroviis. The dominant taiga vegetation is dominated by larch forests. Larch forests are dominant in the composition of prevailing taiga vegetation. These are mainly lingonberry–rhododendron–lichen larch forests and larch forests with lingonberry moss–lichen communities. The communities of subalpine larch forests of the Il’chir tract showed anomalies in the gold contents in samples of fruticose lichens, that is, reindeer lichen. The gold content in lichen samples varies from 0.1 to 0.8, and in some places it reaches 1–3 g/t. In general, in the Sayan alpine landscapes, gold–sulfide vein zones are known to occur in rocks of the Paleozoic volcanogenic–terrigenous formation and at its contact with the carbonate formation. Along the slope, gentle watershed ridges overgrown with taiga larch forests are interspersed with narrow hollows of cryogenic subsidence with the occurrence of boggy willow forests, sedge–cobresia, and ptyagrostis meadows with Dasiphora fruticosa. Only at the foothills, on bedrock terraces with outcrops of rocks of the Paleozoic carbonate formation, communities of the cobresia–fescue alpine steppe are formed.