A sealed vegetation chamber was designed and constructed for physical simulation of climate conditions in the Subarctic zone during the spring–summer time. The small laboratory tundra-simulating ecosystem (TSE) was created for comparative evaluation of the rates of soil respiration and of the total balance of carbon fluxes in tundra ecosystems. The test experiment was performed to study the TSE response to a temperature rise in air and soil by 2°C in terms of the intensity of the СО2 flux. It was shown that this increase in temperature would cause a pronounced shift in the balance of СО2 production and utilization in the ecosystem from near-zero values to a stable generation of 24 μmol/h of CO2 per 1 kg of dry biomass.