Two major phases of the development of landscapes of the foothills of the Western macroslope of the Sikhote-Alin recovered on the basis of a complex study of the section of the deposits in the outer part of the Sakhalin bog, the most extensive bog massif in the lower reaches of the Bikin River. A significant difference in the development of biotic components of landscapes of low mountains during the warming before the last ice age, as well as in the late Holocene, is determined. In the late Pleistocene in the Nizhnebikin depression there was a large shallow lake that has passed several stages of development. For the first time in the upper Pleistocene sediments of Primorye plant macroremains of Schreber's brasenia were found. The development path of the marsh landscape framing the lake was restored. In the last ice age the stratum of clays with traces of cryogenic processing had been formed. The lake had degraded, and the upper parts of the clayey stratum were formed mainly due to gain of aeolian material. At that time, in spurs of the Sikhote-Alin coniferous taiga with dominance of spruce had been represented. In the last 1300 years, on erosion surfaces developed in clays, peatland had being formed. In forest vegetation of low mountains the leading role for the ending of the bog is played by the Korean cedar. Cedar and spruce-cedar forests with participation of broad-leaved species were the most widespread in the Medieval Climatic Optimum. In the little ice age vegetation of the mountain slopes varied a little, while marsh landscapes responded to climate changes more sensitively. In the last 150 years, the bog has entered to transitive to mesotrophic and then mesotrophic stages of development; the role of atmospheric feed has increased; the sphagnum mosses have begun to play a large role in the composition of the peat-forming plants. The role of the pyrogenic factor in the development of local bog vegetation was analyzed.