Soil ecology along an urban to rural gradient in the southern Appalachians
Pavao-Zuckerman, Mitchell Adam
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The urban gradient paradigm was used to investigate the influence of the urban environment on soils in Asheville, NC. A transect of forested plots was established from Asheville, NC to the Pisgah National Forest. The objectives of this study were to: (1) characterize the nature of the urban to rural land use gradient,(2) determine the response of soil physical and chemical properties to an urban environment, (3) characterize the response of the soil nematode community to an urban environment (as an indicator of the soil food web), and (4) determine if urban influences on the soil physical, chemical, and biological environment translate into measurable ecosystem effects. Soil chemical and physical properties were monitored along the gradient. Urban influences on the soil environment were observed. Urban soils were drier, had less organic matter content and were warmer than rural soils along the transect. The soil nematode community assemblage was observed along the gradient. Nematode diversity was not affected by the urban environment. However, the functional composition of the nematode community was influenced by the urban environment. Predatory and omnivorous nematodes were less abundant in the urban soils. Total nematode abundance was also lower in the urban soils. Maturity indices of the nematode community did not strongly reflect this change in the trophic composition of the community. Two ecosystem processes were monitored in this study, leaf litter decomposition and net nitrogen mineralization. The decomposition rate of a standard leaf litter (Quercus prinus) was slower in the urban plots, as evidenced by the ash-free dry mass remaining in the litter through time and the calculated rate constant. Net N-mineralization rates were greater in the urban soils. While litter decomposition rates were not correlated with soil environmental variables, rates of net N-mineralization were influenced by both the soil physical environment and the composition of the nematode community along the urban gradient.