Decomposition of chestnut oak (Quercus prinus) leaves and nitrogen mineralization in an urban environment

We studied soil processes along an urban to rural gradient. To determine the ecosystem response to the urban soil environment, we measured (1) leaf litter decomposition rates using a reference leaf litter, and (2) net N-mineralization and net nitrification rates using paired in situ soil cores. A significant trend toward slower litter decomposition rates toward the urban end of the gradient was observed. In addition, percent ash-free dry mass remaining of the litter was significantly higher during the course of the study but was not statistically significant at the final sampling date. Litter C:N ratio had a complex response with respect to degree of urban land use, and litter % N did not differ between land-use types. Litter decomposition rates were not significantly correlated with observed soil physicochemical and biological characteristics but were influenced by soil moisture and soil organic matter. Net N-mineralization rates were higher in urban soils. Net nitrification rates did not differ with land-use type. Net N-mineralization rates were positively correlated with soil temperature, indicating a response to the urban heat island effect. Net N-mineralization rates were negatively correlated with the numbers of higher trophic level nematodes.