[M-IS01] ENVIRONMENTAL, SOCIO-ECONOMIC, AND CLIMATIC CHANGES IN NORTHERN EURASIA

[MIS01-P17] Temperature regime of Soils of the Tunka Depression

Nadezhda Voropay^1,2、*Anna Ryazanova¹ (1.Institute of Monitoring of Climatic and Ecological Systems of the Siberian Branch of the Russian Academy of Sciences、2.V.B.Sochava Institute of Geography of the Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia)

キーワード：permafrost, anthropogenic influence , adaptation

In the context of modern climate change, studies of the temperature regime of seasonally thawing and seasonally freezing soils are becoming more relevant than in previous decades. Of particular interest are areas located on the border of permafrost. Such territories include some areas of the Irkutsk region and the Republic of Buryatia. Unfortunately, continuous monitoring of soil temperature in these areas has been carried out for no more than 10 years only by scientific groups of some institutes of the Russian Academy of Sciences (IG SB RAS, IZK SB RAS, BIP SB RAS). The network of Roshydromet weather stations has longer series of observations, but here the soils are seasonally frozen, which does not allow us to judge the rates of permafrost degradation. In 2011-2013 As part of comprehensive geographical research at the Institute of Geography named after V.B. Sochava SB RAS, 25 Atmospheric-Soil Measuring Complexes (ASMC) were installed, recording the soil temperature profile in the main landscapes of the Tunka Depression (Republic of Buryatia), including areas of island distribution of permafrost. The sites are located in areas with seasonally thawing soils (wetlands) and seasonally freezing soils (sandy massifs, taiga and forest-steppe areas). Particular attention is paid to soil temperature monitoring, organized in natural and anthropogenically disturbed areas that have been subject to anthropogenic influence at different times: disturbance of natural soil cover, clearing of forests, partial or complete destruction of forests by fires, creation of drainage canals. In order to assess the impact of these disturbances on the intra-annual temperature dynamics, the regime of freezing and thawing of soils in the central part of the Tunka Depression (Southwestern Cisbaicalia), two pairs of sites were established. Each of them has a control site with soil and vegetation in a conditionally undisturbed (or restored to natural) state, as well as a site where the soil and vegetation have undergone significant transformations (fire, cutting and plowing, laying drainage canals). Throughout the year, fluctuations in average daily air temperatures at the sites are synchronous. But due to differences in vegetation cover, microclimatic differences in daily air temperatures reach 4-5C. On the soil surface, the differences between average daily temperatures are slightly higher (7-9C). The distribution of heat in the soil at the sites is also different. The absorption of thermal radiation by soil depends on a number of factors. The factors that determine the temperature regime of soils include: the color of surface horizons, humidity and aeration, which depends on the granulometric composition and structure of the soil, exposure, type of vegetation cover or its absence. The soil in anthropogenically disturbed mineral areas warms up better and cools faster than in natural areas. The penetration depth of the plus 10C isotherm is on average 50 cm greater in anthropogenically disturbed areas. However, tall, dense grass sometimes has a strong insulating effect and can have similar effects to wooded areas. During the cold period, there is no clear relationship between freezing depth and forest cover. The highest negative temperatures are observed mainly in anthropogenically disturbed areas. The monitoring results can be useful in planning environmental protection measures, analyzing, modeling and forecasting extreme natural processes and natural and climatic changes in the region; assessing regional manifestations of global climate change in permafrost landscapes and developing ways of adapting to the consequences of these changes.