Abstract <p>The characteristics of the content of stable and labile carbon, nitrogen, and phosphorus compounds in the humus horizons of Leptosols under five grassy meadows in the mountainous tundra zone of the Khibiny Mountains have been studied. The biological activity of soils has been assessed using the basal respiration rate, the intensity of the transformation of soluble carbon and nitrogen compounds, and the activity of some hydrolytic enzymes. The changes in soil properties under ericaceous dwarf shrubs located among the herbaceous vegetation of tundra grassy meadows have been studied. It is shown that the cumulative effect of ericaceous dwarf shrubs (<i>Empetrum hermaphroditum</i>, <i>Vaccinium myrtillus</i>, <i>Vaccinium uliginosum</i>, and <i>Vaccinium vitis-idaea</i>) on the rate of transformation of carbon, nitrogen, and phosphorus compounds is largely determined by their position in the relief and heat supply. The observed patterns of behavior changes in the studied biophilic elements suggest that the functioning of ecosystems under warming climatic conditions in the mountainous tundra, where the introduction and spread of ericaceous dwarf shrubs takes place, may be accompanied by increased biological activity of soils, in contrast to ecosystems, where these dwarf shrubs were previously a part of the phytocenosis.</p>