Literature Cited


I used ArcView 3.2a (ESRI 1999), a geographic information system (GIS), to manage the necessary data and files. All data was downloaded from the Minnesota DNR GIS Data Deli (MN-DNR 1999), with the exception of the environmentally sensitive areas and City of Northfield land use maps, which were taken from the Northfield Comprehensive Plan (Hoisington Koegler Group 2001). From the Data Deli, I used the following files: USGS Digital Orthophoto Quad (DOQ) 3m (Northfield), Presettlement Vegetation, LandSat-Based Land Use-Land Cover (Vector) (Rice County), Karst Feature Inventory Points, DOT Roads (Rice and Dakota Counties), DNR Land Ownership (Rice County), DNR 24K Lakes, DNR 24K Streams, and DLG Lakes and Wetlands Polygons. The LandSat-Based Land Use-Land Cover (Vector) file for Dakota County was missing, so I used the USGS DOQ to map out natural areas in the Northfield region of Dakota County (ArcView shape file).

I set out to determine which sites would be my habitat “nodes,” or those sites which I would seek to connect via corridors. In an attempt to link the most valuable and diverse habitats, I sought to maximize the amount of land isolated from what is known as “edge effect.” A previous study defined the limits of edge effect as the interior extent of the microclimate gradient created by the edge of one habitat abutting another. The maximum width of this edge zone is 50 m (Machtans et al. 1996). As a result, I chose plots of remaining habitat that were a minimum of 150 m by 150 m, an area which allows for a significant portion of habitat isolated from the edge effect. Twenty such areas were identified and marked. I then connected these marked “nodes” to their nearest neighbors with simple lines (ArcView shape files). These two files, the nodes and the links, were then laid over existing land-use and land-cover files to analyze potential corridors already in existence. I noted corridors in place and then created recommendations for new corridors.

I referred to the Northfield Comprehensive Plan (Hoisington Koegler Group 2001) to provide avenues by which the proposed corridors could be implemented. These recommendations are also accompanied by a set of compromises, or aspects of the plan I see as mutable. The goal of these compromises is to allow the community some flexibility in implementing the plan in the way it sees fit.