Freeze-thaw effect on the processes of transformation of carbon and nitrogen compounds in alpine meadow soils

Freezing-thawing of alpine meadow soils results in a 1.5- to 2-fold increase in the contents of extractable organic and inorganic nitrogen and organic carbon compounds, whereas the contents of microbial biomass nitrogen and carbon slightly decrease. The latter are quickly restored in the course of subsequent incubation, but the processes of transformation of nitrogen compounds proceed differently in soils that are subject to freezing under natural conditions and in nonfreezing soils. In nonfreezing soil, an abrupt activation of organic nitrogen mineralization and nitrification takes place against the background of a relatively low level of microbial assimilation of inorganic nitrogen compounds by microorganisms.