Installation of impervious surface in urban areas affects microbial biomass, activity (potential C mineralisation), and functional diversity of the fine earth

Artificial soil sealing in urban areas has attracted increasing attention due to its potential hazard to urban ecosystems. It has negative impacts on soil function and the urban environment, since the impervious surface can hamper the exchange of material and energy between the soil and other environmental compartments. However, information about the effects of artificial soil sealing in urban area on soil quality and properties, especially the microbiological components, is still limited. Ten plots which differed in land use were selected from Nanjing City, China, to investigate the effects of impervious surfaces on microbiological characteristics in urban soil. Plot types were paved road, residential paved square, residential paved alley, and grassed area. Soil microbial biomass carbon (Cmic) and nitrogen (Nmic), and activities were analysed, and the microbial functional diversity of fine earth (<2mm material) was characterised by the Biolog EcoPlate technique. Mean concentrations of soil organic carbon (SOC), Cmic, and Nmic in fine earth from the impervious areas (0–20cm) were, respectively, 6.5gkg-1, 55.8mgkg-1, and 12.2mgkg-1, which were significantly lower than concentrations from grass areas. Urban sealing also resulted in decreases in soil microbial activity and functional diversity, but the influences on soil microbial diversity varied among land uses, with road pavement having the most negative effect. Substrate use patterns showed that microorganisms in urban sealed soils had higher utilisation of polymers (P<0.05) but lower use of carbohydrates and amines/amides (P<0.05). These findings demonstrate that SOC in the sealed soils was more stable than in open soils, and the installation of impervious surfaces such as asphalt and concrete, which are very common in urban areas, can result in decreases in SOC content, soil microbial activity, and diversity in urban soil.