Soil carbon and nitrogen availability are key determinants of soil microbial biomass and respiration in forests along urbanized rivers of southern China

Although soil microbial communities have been known to play integral roles in most terrestrial biogeochemical processes, surprisingly the patterns and controls of soil microbial communities across urban forest ecosystems are poorly understood. To contribute towards addressing this critical gap, we examined the patterns of soil microbial properties and the effects of soil chemical properties on these patterns in forest ecosystems along the two rivers with different urbanization levels in the coastal city of Fuzhou in southern China. Soil microbial biomass C (MBC), microbial biomass N (MBN) and soil microbial respiration rate (SR) significantly decreased from the highly urbanized Bailongjiang River (BJR) to the less urbanized Wulongjiang River (WJR) and from the 0 - 10 cm soil depth to the 10 - 20 cm soil depth. Soil MBC/MBN and metabolic quotient (qCO(2)) values in BJR forest stands were not considerably different from those of WJR forest stands. Soil C and N availability determined soil MBC and MBN patterns and these four aforementioned soil variables determined SR patterns across the rivers and soil depths. Our study contributes to a better understanding of the patterns and controls of soil microbes and their activities in forest ecosystems with different urbanization levels.