Background/Question/Methods   While extensive ecological research has taken place on forest, grassland, and urban ecosystems, little is known about C and N dynamics in exurban landscapes (human dominated with low housing densities), which are undergoing rapid expansion. In our study system of SE Michigan, USA, residential development is occurring primarily on former agricultural land. Prior research conducted on forest aggradation following agriculture may provide an upper bound on C and N accumulation in residential landscapes. Numerous trees and shrubs are present, but they are interspersed with large areas of turf grass and are actively managed by residents. Litter is also managed actively, which should impact soil pools of C and N. In this study we examined how residential development type (in four categories that varied in tree cover) and time since conversion to residential land (10 to 50 years) controlled the rates of accumulation of landscape scale C and N. We used combined relevé and quadrat sampling methods to quantify plant community composition, woody plant sizes, and C and N pools in soil and vegetation in 26 exurban neighborhoods in 10 townships. We combined this with GIS analysis and aerial photointerpretation to scale to the landscape and trace landscape histories.

Results/Conclusions   In our sample of 26 neighborhoods, 65% were undeveloped in 1960. Development rates peaked in the 1960s but continued through the 2000s. As expected, significant spatial heterogeneity was observed in vegetation communities in residential land. These differences can be directly attributed to human activity through actions of developers and residents. While turf grass alone and turf grass combined with woody vegetation were the most common vegetation community types, several other vegetation types were identified including dense tree cover (forest), wetland, grassland, and mixed herb and shrub (garden). Among vegetation types that contained woody vegetation, 55 different species were identified. Preliminary results for biogeochemical pools indicate that differences in carbon and nitrogen pools were observed across vegetation community types, the distribution of which differed by type of residential development. Within some vegetation community types, such as those with woody vegetation, C storage increased with time since development over the 5 decade period.