ИСТИНА

Nevertheless the annual rate of increase of Greenhouse Gases (GG, primarily carbon dioxide) amount in the atmosphere is well known, it still remains unclear the relative input of their specific terrestrial natural and anthropogenic sources and sinks. Amongst those, the importance of different types of human land use is especially poorly studied. To do this, one way is to evaluate the most easy determined decomposition component of C-balance, i.e. soil emission, since it comprises in terrestrial ecosystems 60-99% of Gross Respiration. Permafrost soils occupying 15% of land surface (mostly in Eurasia and North America), contribute about 25% of total terrestrial carbon in frozen state. Nevertheless the biogenic GG soil emissions from permafrost is only 5% of the global, this makes those soils of high importance in the warming world. Field measurements of CO2, methane and nitrous oxide were conducted in Aug-Sept 2014-2017 in natural and human-modified (HM) biotopes in 37 tundra, steppe and forest permafrost sites of Russia and Svalbard. It is shown that depending on nature and duration of anthropogenic influence (AI), or the types of ecosystems, it is observed either increase or decrease in soil emission of biogenic GG compared to natural rates. Nevertheless, acting together land use factors provide an additional net source of CO2 to the atmosphere with high probability. This is due to the imminent elimination of Primary Production and the delayed CO2 emission from soils resulted from heterotrophs respiration. HM methane sources depending on the type of AI could show positive (emission increase) or negative (emission reduction) effect on radiation forcing of the atmosphere, whereas anthropogenic sources of N2O have only positive effect. Despite weather changes, HM sites in all years of observations show consistently greater rates of CO2 emissions compared to the natural analogues. Calculations show that local anthropogenic soil GG emissions are comparable with the impact of Climate Change over the same period. Ultra-continental cryogenic soils (UCC) of Siberia demonstrate greater emission rates of CO2 than either natural or AI soils in the Arctic, with higher rates in forest stands as compared to steppe biotopes. The Birch effect is less expressed in UCC than in European soils. We hypothesize that first is mostly due to more expressed cryogenic microcracks, whereas the second is resulted from adaptation of UCC soil biota to extreme dryness and freezing.