The Development of the Natural Environment in the Valley of the Knevichanka River in the Middle and Late Holocene (Southern Sikhote-Alin)

Autor: T. A. Grebennikova, P. S. Belyanin, N. I. Belyanina
Rok vydání: 2021
Předmět:
Zdroj: Geography and Natural Resources. 42:71-79
ISSN: 1875-371X
1875-3728
DOI: 10.1134/s1875372821010054
Popis: This paper presents a reconstruction of the history of development of the ecosystems in the lower reaches of the Knevichanka River over the past 5350 cal BP based on the biostratigraphic analysis of the sediments of the first terrace above the floodplain. Differences were identified and characteristics were determined in the vegetation structure during the final phase of the Holocene climate optimum and multidirectional climatic fluctuations in the Late Holocene. It has been found that in the final phase of the Holocene broad-leaved plants were more widespread on the mountain slopes than at present. The alluvial plains predominantly contained grassy meadows with small-leaved plant communities. Mixed forests prevailed in the vegetation on the slopes of the Knevichanka River valley with a dominance of Korean pine, Japanese red pine, oak, elm, Amur cork tree, linden, 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 Lakes Krolevetskoe and Orlovskoe, an extensive shallow sea bay existed, which was connected to the Ussuri Bay via a narrow strait. A cooling period that began at the end of the Middle Holocene and continued into the beginning of the Late Holocene led to a reduction of broad-leaved plants in vegetation and 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 seawater, and the upper part of the shallow bay was detached from the sea. A lagoon occurred at the location of the marine gulf. The lagoon became gradually freshened, shallow, and connected to the sea by the channels of the Knevichanka and Artemovka rivers. However, during the syzygial tides and wind-induced surges, seawater still intruded regularly. At the end of the Late Holocene, the valley of the Knevichanka River developed natural conditions, thus giving rise to the recent structure of vegetation. Desalination occurred in lakes Krolevetskoe and Orlovskoe, while they acquired their recent outlines.
Databáze: OpenAIRE
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