Известия Томского политехнического университета: Инжиниринг георесурсов (May 2019)
Detailed reconstruction of bog functional state as response to continental climate changes in Holocene (the middle taiga of West Siberia)
Abstract
The relevance of the discussed issue is caused by the need to develop short-term forecasts of the landscape functional state and climate of Western Siberia considering regional mire response to the changes in the Holocene climate. The main aim of the study is the detailed reconstruction of the dynamics of plant communities, water regimes and peat accumulation of middle taiga bog considering the influence of paleocryogenic processes. The methods used in the study: detailed (1-5 cm) study of the macrofossils composition and physic-chemical properties of peat, radiocarbon dating (13 dates) peat deposits; reconstruction of phytocenoses and water regimes by traditional paleoecological methods, reconstruction of paleocryogenic processes based on the system-evolutionary methodical approach of searching violations in autogenous mire development and complex of bio-indicators from permafrost zone; author's method of adjusting the chronology with account of peat accumulation stopping; comparative analysis of the obtained data and regional climate reconstructions. The results. The author has carried out the reconstruction of the dynamics of plant communities, water regime and peat and carbon accumulation and identified numerous violations of autogenous bog development caused by frequent changes in climate hydrothermal regime and paleocryogenic processes. Initiation and pulsating character of paludification of well-drained sandy terraces are cused by the influence of degradation of waterproof permafrost ca. 7145 cal. BP, and its formation ca. 6520 cal. BP. Peat accumulation stopping ca. 4600-3950, 2150-1770 and 1550-1340 cal. BP is conditioned by formation of Palsa in dry cooling and thermokarst pools in the subsequent warming. Along with pools and their floating, the wettest stages of development were ca. 5350, 3760, 3264, 3025, 2852, 1120-920, 870-600 cal. BP. Long-term carbon accumulation rate is equal to 20,4 g m-2 yr-1 with maximum rates 40,6-45,0 g m-2 yr-1 in cooling, mostly wet ca. 3170-2815 cal. BP, wet warming and cooling ca. 1000-560 cal. BP. It was shown that account of paleocryogenic processes, use of date-analogs and peat layer-analogs can significantly improve the quality of the reconstruction of the mire functional state and obtain objective dates on dynamics of peat and C accumulation.
