|
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.
|
|
