PARENT SESSION
Oral Session - Human Influences on Landscape and Watershed Processes Chair(s): Lopez, Ricardo ¹, ¹ Landscape Ecology Branch, Las Vegas, NV
Wednesday, March 31, 2004 1:00 PM - 4:20 PM Zeus Room B

Using Flow Distance to Proximally Weight Land Use. ^*HOLLENHORST, THOMAS P. ¹, JOHNSON, LUCINDA B. ¹, HOST, GEORGE E. ¹ and RICHARDS, CARL ², ¹ Natural Resources Research Institute, Duluth, MN, USA² Minnesota Sea Grant Program, Duluth, MN, USA

ABSTRACT- Understanding the linkages between particular stressors and ecosystem responses is crucial for establishing useful environmental indicators. Yet, these linkages are rarely straightforward. Although we know that certain types of ecological stress (i.e., urban or agricultural development), affect certain ecosystem functions and biological communities, these effects are rarely linear or easily predicted. A stressor's frequency, intensity, duration and return interval can all alter an ecosystem's response to anthropogenic stress. Tobler's First Law of Geography states: "Everything is related to everything else, but near things are more related than distant things". Therefore, the distance between the stressor and exposed population will likely impact the intensity, duration and possibly the type of exposure to anthropogenic stresses such as land use. Digital elevation models, combined with watershed analysis tools, provide the means to measure distance while incorporating flow direction. These measures of flow distance then provide a means to add "proximal weighting" to more basic summaries of watershed land cover proportions. We mapped land cover in 36 watersheds in Southeastern Minnesota and used a digital elevation model to determine flow direction and flow distance within each watershed. We used flow distance as a weighting factor to compare land cover composition to in-stream properties including; nutrients, chlorophyll A, percent fines, maximum temperature, number of fish species and invertebrate community structure. Results show that distance can be incorporated with basic watershed metrics to better predict in-stream properties.

KEY WORDS: watershed analysis, Flow Distance , anthropogenic stress, environmental indicators, Digital elevation models