COS 86-5 - Understanding urban forest structure of residential landscapes in the Seattle metropolitan urban(izing) region

Thursday, August 11, 2011: 9:20 AM
Ballroom B, Austin Convention Center
Karis R. Tenneson, Urban Design and Planning, University of Washington, Seattle, WA
Background/Question/Methods

In coupled human-natural systems, vegetation simultaneously provides ecological function (i.e., carbon storage) and human services (microclimate). However plant communities are significantly altered by urbanization as development fragments natural cover and land management alters community composition. We have learned a great deal about vegetation structure and function in urbanizing environments. Yet most studies do not adequately represent the heterogeneity of urban land uses and patterns along an urban gradient. Understanding the role of residential developments in maintaining vegetation is important since residential lands constitute the majority of urban regions. Household landscape management activities have the capacity to substantially affect urban ecosystem services.

In my research I ask how urban forest structure within single-family residential land use varies with different urban patterns across a gradient of urbanization. I characterize vegetation structure and quantify aboveground carbon storage. The residential parcel, my unit of analysis, provides a direct link between land managers, households, and vegetation patterns. I surveyed plant communities on parcels, stratified by an urban gradient and five land cover types derived from LandSat imagery (mixed deciduous, conifer, heavy, medium and light urban). I measured diameter at breast height and identified trees on 100 parcels. I quantified carbon storage using established allometric equations.

Results/Conclusions

My preliminary results show that areas with conifer land cover have the highest amount of carbon storage, followed by mixed deciduous forests. Not surprisingly, carbon storage decreases with increasing levels of impervious surfaces (represented by heavy, medium and light urban land covers). After controlling for lot size and land cover type, low density suburban areas store slightly more carbon than more urbanized, high density regions. In addition, non-vegetated, impervious surfaces dominate heavily urbanized regions. My results highlight the importance of creating and maintaining public parks and open spaces in order to provide heavily urbanized, high density neighborhoods with local ecosystem services provided by vegetation in order to maintain quality of life for residents. In addition, the results from this research can inform strategies for increasing tree cover and the associated ecosystem services on private lands, especially in suburban regions. Because residential lands cover more area than other urban land types, household landscape management activities have the capacity to substantially affect levels of local ecosystem services, such as carbon storage.

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