Microbial Respiration in Subtropical Urban Soils Depending on Vegetation Type

ABSTRACT

Urban vegetation combines invasive and introduced species with native relics, whose litter is the primary source of organic matter inputs in urban soils. Plant litter quality regulates both organic carbon (C) storage and microbial activity in urban soils. Here we examined the microbial respiration and organic C stocks in the subtropical urban soils depending on plant litter decomposability. Five urban areas differing in vegetation (deciduous forest, shrubland, grassland, ruderal area, and turfgrass) were used for kinetic analysis of plant litter decomposition over a 12‐week incubation, and CO ₂ efflux and microbial biomass C in soil were analyzed. The plant litter decomposability decreased as its C/N ratio increased. The decay constant of potentially mineralized litter components decreased progressively from turfgrass and grassland to shrubland and ruderal area, and finally to forest. Higher litter decomposition was associated with a faster rate of soil microbial respiration per unit of organic C content. Soil organic C stocks were 20%–38% larger in urban forest and areas with ruderal vegetation than in turfgrass. This was caused by the greater biostability of forest litter and lower microbial activity in the soils of semi‐natural areas compared with those of completely transformed and managed urban ecosystems such as turfgrass. Consequently, the decrease in decomposability of plant litter increased organic C stocks and reduced microbial respiration rates, highlighting the importance of vegetation type in managing C storage in urban soils.