Effects of below ground CO₂ emissions on plant and microbial communities

Below-ground carbon dioxide (CO₂) emissions occur naturally at CO₂ springs, but the risk of occurrence at other sites will increase as geologic CO₂ storage is implemented to help mitigate climate change. This investigation examines the effects of elevated soil CO₂ concentrations from such emissions on vegetation biomass and microbial community biomass, respiration and carbon utilisation in temperate grassland. Soil CO₂ concentrations was increased by release of concentrated CO₂ gas from a point source 0.6 m below the surface of the soil as a low-level leak (1 l min?1) for 10 weeks. The gassing resulted in reduced vegetation above- and below-ground biomass over time. No significant changes in microbial biomass or carbon utilisation were observed, but a trend towards reduced microbial respiration was apparent. This research provides a first step towards understanding the potential ecological risks of geologic carbon storage, the development of biological leak detection methods, and improved understanding of the effects of elevated soil CO₂ concentrations on biological communities.