Microbial Assimilation of Atmospheric C0_2 to Synthesize Organic Matter in Soils

摘要

There are no reports on the activity and quantitative capacity of microbial atmospheric carbon dioxide (CO2) assimilation in terrestrial ecosystems, although such CO2 assimilative microorganisms are numerous and widespread. Both non-phototrophic and phototrophic microbial CO2 assimilations were investigated in two sets of microcosms of eight selected soils in a closed, continuously carbon-14 (14C)-labelled CO2 atmosphere chamber. A significant amount of 14C-labelled CO2 was incorporated into the microbial biomass, accounting for between 0.12 percent and 0.59 percent of the soil organic carbon (average 37.8 ± 19.4 mg/kg after 80 d, CV = 51.3 percent, n = 8) in the set exposed to artificial light (about 500 mmol-photons-m"2-s_1 parabolic aluminized reflector light [PAR]), whereas none was detected in the set in the dark condition. Hence, soil phototrophic CO2 assimilation represents a significant part of microbial activity which cannot be ignored since it is estimated to have an annual organic C assimilative capacity of 4.9-37.5 g-C/m.