Nitrogen is a major limiting factor in most temperate and boreal ecosystems which substantially impacts on net primary productivity. An exotic tree species may affect ecosystem properties by altering nitrogen dynamics. To test this possibility, a series of sites were established in the greater Baltimore area. The urban landscape provided a higher proportion of exotics, but also a number of potential confounders. Soil moisture content, not urbanization, was the greatest confounder in this study. Soil moisture was significantly (p < 0.05) correlated with the soil properties of initial NO3-, initial NH4+, denitrification enzyme activity (DEA), nitrification, and microbial biomass carbon and nitrogen. Sites with Ailanthus altissima (Mill.) Swingle, had significantly higher values (p < 0.05) for soil moisture, initial NO3-, nitrification, and DEA than sites with native species or Acer platanoides L. Ailanthus sites were also significantly lower in initial NH4+. Since all of these variables respond strongly to moisture, they are most likely an effect of soil moisture content and not vegetation. However, the distribution of soil moisture does appear to be closely tied to the presence of Ailanthus. If Ailanthus is affecting the moisture content of a site, it could have secondary impacts on ecosystem processes and site quality.