Home – Home – Jornals – Geography and Natural Resources 2021 number 1

Based on the biostratigraphic analysis of the sediments of the first terrace above the floodplain, the history of development of the ecosystems of the lower reaches of the Knevichanka River over the past 5350 cal BP was reconstructed. Differences were identified and characteristics were determined in the structure of vegetation cover during the final phase of the Holocene optimum and during multidirectional climatic fluctuations in the Late Holocene. It is found that broad-leaved plants in the final phase of the Holocene were more widespread on the mountain slopes than at present. The accumulative plains were dominated by grassy meadows with small-leaved plant communities. Vegetation on the slopes of the valley of the Knevichanka river was dominated by mixed forests, with a predominance of Korean pine, Japanese red pine, oak, elm, Amur cork tree, lime, lilac, Manchurian walnut and other species. In the lower reaches of the Knevichanka river, in the place of the marshy plains and water areas of Lake Krolevetskii and Lake Orlovskii there existed a extensive shallow sea bay that was connected in a narrow strait with Ussuri Bay. A cooling period that began at the end of Middle Holocene and continuing at the beginning of Late Holocene led to a reduction of broad-leaved plants in vegetation and to a more widespread occurrence of small-leaved plants. At that time the formation of the soil layer of the first terrace above floodplain began in the lower reaches of the river. In the course of the marine regression, the coastal lowlands became free from sea water, and the upper part of the shallow bay was detached from the sea. A lagoon was formed on the place of the marine gulf. The lagoon became gradually desalinated, shallowed and began to connect with the sea by the Knevichanka and Artemovka channels. However, during the syzygial tides and wind-induced surges, seawater was still penetrating it at regular intervals. At the end of the Late Holocene, the valley of the Knevichanka river developed natural conditions giving rise to the modern structure of vegetation. Desalination of Lake Krolevetskii and Lake Orlovskii occurred, the outlines of which acquired the modern position.