Changes in the Soil Carbon Dioxide Efflux in Forest Ecosystems Caused by Technogenic Pollution in the Kola Subarctic

摘要

The total soil CO2 efflux and its constituents were analyzed along the gradients of pollution of forest ecosystems by the emissions from nonferrous metallurgy plants in the Kola Subarctic. The CO2 efflux from the soil surface was measured by the closed chamber method. The summer efflux was calculated using the regression dependences of CO2 emission on air temperature. The root and microbial respirations were separated using the field method of substrate-induced respiration. The soil CO2 efflux reached relatively high values in the background pine (200 g C/m(2)/summer), birch (460 g C/m(2)/summer), and spruce (420 g C/m(2)/summer) forests. The bulk of CO2 produced in the soils under these forests was due to root respiration (45-70%). Closer to pollution sources, a decrease in microbial and plant biomass, depletion of mineral nutrients, and accumulation of heavy metals were observed in soils. As a result, the CO2 efflux decreased by up to 1.5 times in the zone of defoliation of the trees, 10 times in the zone of technogenic sparse forests, and 20 times in the zone of technogenic barrens. Defoliation of forests was accompanied by some activation of microbial respiration because of the additional input of nutritional substrate for microorganisms. The degradation and death of vegetation resulted in an expectable decrease in root respiration and its complete suppression in technogenic barrens. The results of this study indicate that monitoring of the soil CO2 efflux helps to identify the specific features in the functioning of forest ecosystems during technogenic degradation and to develop efficient methods for their remediation under industrial pollution in the Arctic.