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Holland, Amanda K.

Rubenstein School of Environment and Natural Resources

2008

M.S.

Urbanization has been found to alter soil properties and processes that can have important influences on critical ecological functions such as carbon, nitrogen, and phosphorus cycling. As urban areas continue to grow and expand, a better understanding of the impacts resulting from residential development and homeowner lawn management is important to quantify how nutrients behave in the urban environment. The main objectives of this study were to determine if soil quality differed in residential developments as a function of increasing time since development (lawn age), increasing development intensity (population density and average surrounding parcel size (APS)), and lawn management practices (current fertilizer use). Soil quality was defined on the basis of soil properties and processes that included: total carbon (TC)and nitrogen (TN) content, microbial biomass carbon (MBC) and nitrogen (MBN), soil respiration, potential nitrogen mineralization (PNM), and potential net nitrification (PNN). Sixty-five lawns were sampled from August and September of 2006 in Chittenden County, Vermont, USA. Student t-test, Pearson Correlation analysis, and multivariate linear regressions were used to identify relationships with soil quality indicators and lawn age, urban intensity, fertilization, and natural soil properties. We found that characteristics of residential land use play a role in the ecological functioning of urban soil. Similar to previous research, our study identified a positive correlation with the age of the lawn to organic components of soil such as OM, TC, TN and biological microbial biomass across a broad sampling of sites. Lawn fertilization practices had significant effects on soil indicators in which, currently fertilized lawns (53%) had significantly lower soil respiration, TC, and OM (p-value 5 0.05) and significantly higher PNM compared to lawns currently non-fertilized (47%). The results identified that homeowner management influenced the soil nutrient pools and may indicate that current fertilization can accelerate OM breakdown or currently fertilized soil may allocated less soil organic carbon belowground. Although we found urban intensity significantly influenced microbial biomass and PNN, it did not play a large role in explaining variance in the soil quality indicators. As development density captures multiple characteristics of the residential urban area, the density impact on lawn systems may be obscured with correlated factors. Additionally, urban density many not be the right predictor to capture the influence of development patterns in less urbanized areas like Chittenden County. Through this study we can conclude that residential areas in Chittenden County, VT differ in soil quality with homeowner lawn management practices and temporal trends from development patterns. The identification of these individual factors of residential lawns can be used to characterize residential neighborhoods and identify how development (single age versus multi-age neighborhoods) and lawn management patterns interact in a watershed and implications they may have for retaining and exporting nutrients from the soil environment.