On the basis of a comprehensive study (botanic, diatom, and pollen analysis) of the two peat bog sections of the Sergeev Plateau, the development of the natural environment of midlands of the Southern Sikhote-Alin was reconstructed for the last 4.9 ka. Radiocarbon dates and position of marker volcanic ash layer B-Tm of the Baitowshan Volcano erupted in the X century were used to define the event chronology. An age-depth model was made and peat accumulation rates and ash content of the peat were analyzed. It was established that the belt of dark coniferous forests on the elevation about 900 m was relatively stable, while multidirectional climatic changes led to sharp changes in the dominant peat-forming plants. Unstable climatic conditions in many respects caused the peculiarities of the hydrological regime of the bogs. The fall in the groundwater level and the strengthening role of atmospheric supply, as a rule, was associated with cold events. One of the factors determining the development of landscapes was