Decomposition of labile and recalcitrant litter types under different plant communities in urban soils

Although little is known about the relationship between aboveground and belowground biota and ecosystem services in urban soils, the scarce data suggests that plant coverage has a key role in influencing the urban C and N cycles. Plant litter quality and quantity have been addressed as one the major factors determining the rate of nutrient and organic carbon cycling in urban soils. However, the land-use history of urban soils, frequency of disturbances and abiotic-biotic conditions may largely contribute to the effects of aboveground biota on decomposition process. Here we studied the decomposition process of different litter types (labile and recalcitrant litter) in two structurally and chemically divergent urban soils (landfill sandy soil and richer park soil). At both of these urban sites, a reciprocal litter placement experiment was performed to distinguish the effects between plant coverage (plant treatment) and litter type on litter decomposition processes. As hypothesized, labile litter decomposed faster than recalcitrant litter at both urban soil types. Urban soil type however, had a clear impact on degradation rate of the litter: all litter types decomposed at higher rates in park soil with higher organic matter and soil moisture content. Unexpectedly, the plant treatment did not affect the degradation rate of the litter although it did have a significant influence on the abundance of litter-inhabiting Collembola in landfill soil. Our study suggests potentially higher carbon retention in urban soils under recalcitrant litter producing plants in comparison to plant-soil systems with labile-litter producing plants.