Effects of urban habitat types and landscape patterns on ecological variables at the aboveground-belowground interface

Ecologists have not studied urbanized ecosystems extensively even though they are increasing in area globally. For this thesis, three approaches were used to investigate the effects of urban habitat management on ecological variables: (1) an observational study of soil microarthropods in high- and low-maintenance lawns and unmanaged fields; (2) a manipulative study in which soil properties, microclimates, carbon and nitrogen cycles, and invertebrates were measured in plots of lawn, old field, bark mulch and gravel mulch habitat types; (3) a microlandscape study in which the effects of landscape context patterns on arthropods in lawns were tested. In study 1, soil mites were more numerous in high-maintenance lawns while collembolans were more abundant in low-maintenance lawns. In study 2, all measured variables differed significantly among the habitat types. Mulch plots were warmer during daytime hours and had wetter soils as compared to vegetated plots. Gravel plots had the lowest soil organic matter, soil aggregate stability, and earthworm densities. Bark mulch plots had the largest earthworm populations and lowest soil bulk density. Earthworm numbers were intermediate in unmowed and lawn plots, except when they decreased in lawns during drought conditions. Fluxes of carbon dioxide were higher from soils in lawn and bark mulch plots. Decomposition rates of oak leaves in litterbags were greater in mulched plots as compared to vegetated plots. Mowing and mulching promoted higher levels of inorganic soil nitrogen at certain times relative to those in old field plots. In field measurements, nitrous oxide fluxes were highest from gravel-covered soils. Arthropod communities differed significantly among the habitat types although no consistent patterns were seen in relationships between activity-abundance levels and the habitat types. In study 3, arthropod communities differed among patches of lawn surrounded by different levels of landscape heterogeneity, and activity-abundance levels tended to be higher in microlandscapes containing non-lawn habitat patches as compared to those with only lawn. Habitat composition may have influenced the results of this study more than landscape heterogeneity. Data from these studies can be used to guide sustainable landscape management practices that seek to conserve valuable biodiversity and ecosystem services in urbanized ecosystems.