On the territory of the Republic of Buryatia due to global climate change, significant transformations of the natural environment have been observed. Statistically significant trends of increase in temperature and decrease in precipitation with identification of wet and dry periods have been established. In the last 20 years due to the abnormally high air temperatures and the increasing aridity of the territory, the frequency and area of fires have increased, the rate of permafrost degradation on the southern boundary of the permafrost zone in the soils of meadow-steppe landscapes has increased twice.
The basis for assessing the stability of geosystems to changes in external heat cycle conditions is the calculation method. It is shown that permafrost soils are characterized by increased values of annual heat cycle QY ≥ 300 MJ/m2, i.e., half-sum of heat arrival and flow rate per year. This is due to the high heat consumption for melting soils (QPh = 0.7–0.8 QY) and warming them in the negative temperature range (QF). The heat cycle in frozen soil (QF) always has more heat cycle than in the thawed soil (QH). The condition QF > QH means the dominance of processes occurring at negative temperature, and the difference QF − QH is a quantitative assessment of the energy stability of soils to changes in heat exchange conditions on the surface.
The soil cover patterns in the subtaiga landscapes on the northern spurs of the Tsagan Daban Ridge in the Selenga Mountains have been studied. Gray humus lithozems and bedrock outcrops are typical of the steep south facing slopes under herbaceous pine forests. Soddy iron illuvial podburs are formed under forest vegetation on gentle slopes of northern and western aspects with a thick mantle of loose colluvial depos its. Dark humus metamorphic soils occur on the slopes of western and northwestern aspects below 700 m a.s.l. under secondary forb-grassy communities that replaced the initial herbaceous pine forests. Windblown hollows (yardangs) are occupied by humus psammozems under steppe pine forests. The morphological and physicochemical characteristics of these soils are discussed in the paper.
Impacts of wildfire low-severity on soil properties on 2 sampling plots of the dry pine forest in Western Transbaikalia are studied. Low-severity surface fires in the studied pine forests have a positive effect, since they activate the processes of litter decomposition and further dissolution of organic substances that provide soil and plants with accessible elements. Pyrogenic morphological features persist for a long period after a fire. These include the presence of black carbonaceous subhorizon at a depth of 14-14.5 cm, ocher mottles along the roots of burnt trees. These features are shown in the increased content of iron in the Tamm extract and exchangeable bases. This creates conditions for the fixation of humus associated ПРИРОДА ВНУТРЕННЕЙ АЗИИ № 4(22) 2022 NATURE OF INNER ASIAwith both calcium and iron hydroxides. Also there is a slight increase in the content of the clay fraction. Two years after the fire the properties of the soil change significantly. Eleven years after the fire, most soil properties are quickly restored to pre-fire levels.
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