Minnesota Stewardship Spatial Analysis Project
Methodology and Analysis documentation
January 28, 2008
Summary
In the fall of 2004, Minnesota DNR and the U.S. Forest Service began working
together to create a digital database of existing forest stewardship plans and also
a GIS layer representing the level of “benefit” gained from potential forest
stewardship work. This document summarizes the GIS methods used to create
the stewardship priority spatial assessment.
Methodology
Following the lead of other states (including Connecticut and Missouri),
Minnesota identified 12 factors that contribute to the overall benefits gained by
active forest stewardship across the State of Minnesota. These factors were also
weighted in terms of their importance relative to each other. The table below
shows the factor, its weight, and corresponding percent of the total weight:
FACTOR
1. Private Forest Ownership
2. Riparian Areas
3. Forest Patch Size
4. Wetlands
5. Slope
6. Impaired Watersheds
7. Public Water Supplies
8. Rare and Natural Features
9. Risk of Forest Pests
10. Proximity to Public Lands
11. Risk of Development
12. Risk of Fire
TOTAL
WEIGHT
3.0
2.1
2.0
1.6
1.5
1.4
1.3
1.3
0.9
0.8
0.6
0.5
17.0
% OF TOTAL
17.6
12.4
11.8
9.4
8.8
8.2
7.6
7.6
5.3
4.7
3.5
2.9
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In order to create a spatial model or map showing the benefits of forest
stewardship programs based on these criteria, a GIS layer (displayed in the
Forest Stewardship Potential map on the following page) was created to
represent the spatial distribution of each of the factors above. The remainder of
this section describes how those layers were created.
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1. Private Forest Ownership
This layer was created from the land
cover layer and land stewardship layer
created during Minnesota’s Gap
project. Lands that were identified as
“Forested” from Gap land cover and
lands that were classified as “Small
Private & Miscellaneous or Large
Private Non-Industrial” from Gap
stewardship were used to create this
layer. These lands are drawn in
purple on the map to the right.
2. Riparian Areas
A new riparian layer was created by
buffering lakes, streams and open
water wetlands by 300 feet. Lakes
and streams were identified from an
existing DNR layer digitized from
1:24,000 topographic maps, and open
water wetlands were identified by
using the existing NWI layer for
Minnesota. These riparian zones are
identified in green on map to the right.
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3. Forest Patch Size
The forest patch layer was created
with the Gap land cover map. The
forest and non-forest land cover layers
was clumped and sieved to only
include forested clumps greater than
20 acres in size. Those patches are
shown in magenta at the right.
4. Wetlands
The wetlands layer was created by
identifying everything in the Minnesota
NWI layer that was not upland.
Colored in blue at the right.
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5. Slope
The slope layer was created by using
the 30 meter Digitial Elevation Model
for Minnesota. All lands that had
slopes of greater than 12% or less
than 60% were identified as high
value for stewardship, and are colored
purple in the map to the right.
6. Impaired Watersheds
The impaired watersheds layer was
created by selecting Minnesota
Pollution Control Agency impaired
streams and lakes and selecting all
associated watersheds from the DNR
minor watersheds layer. Impaired
watershed locations are shown in
orange at the right.
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7. Public Water Supplies
This layer was based on data provided
by the Minnesota Department of
Health. Any area with a “vulnerability”
rating of “Low”, “Moderate”, “High” or
“Very High” in the drinking water
supply shapefile was selected and
added. In addition, any polygon
defined in the Source Water
Assessment area shapefile was added.
The resulting layer, shown in maroon
to the right, shows areas with
vulnerability problems as well as high
priority “source water” regions. Future
layers will presumably address this
criterion better, but in the interim the
layers above provide a reasonable
surrogate.
8. Rare and Natural Features
In order to protect any features with
ecological significance that have been
identified and mapped, the County
Biological Survey natural features
database was accessed. The map at
the left displays buffers of ½ mile in
diameter, and the selected feature is
within that buffer. This “shift” was
performed to protect the true location
of the rare and natural features.
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9. Risk of Forest Pests
A national “risk mapping” effort
performed by the U.S. Forest Service,
Forest Health Technology Enterprise
Team formed the layer used to
identify forest areas at risk of mortality
from insect and disease infestation.
This layer was a national effort, and as
such the resolution of the data is 2
kilometers by 2 kilometers. Areas at
risk are shown in red.
10. Proximity to Public Lands
All public lands, identified as “State”,
“Federal” or “County” by the Minnesota
Gap Stewardship layer, were buffered
by ½ mile to create the layer shown to
the right. The orange lands also
include the public lands themselves,
but the actual public lands were
masked out of the analysis (described
below), leaving a ½ mile buffer as a
priority area.
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11. Risk of Development
This analysis followed the direction of
other states and made use of the
census block data. Those data were
classified into 4 categories: Urban,
Exurban, Suburban and Rural. Each
category had a corresponding numeric
code from 1 – 4. This was done for
both 1990 and 2000 census year data.
Then, we simply subtracted the 1990
grid values from the corresponding 2000
values. In the resulting grid, any value
greater than 0 represented a census
block that “grew” in density from 1990
to 2000. We used the associated areas
to represent areas of “growth” in the
State, and they are shown in grey to the
right.
12. Risk of Fire
This grid shows areas at elevated risk
from wildfire damage. It was created
from the Minnesota Gap Fuel Hazards
map by selecting all values of “high”,
“high 1 (grass)” or “moderate”. Also,
values from the Wildland Urban Interface
layer that showed “interface” were
added. Any above value in either of
these layers resulted in a ‘1’ in the Fire
Risk layer shown in orange to the right.
This layer simply tended to follow the
forest location and was weighted lowest
of all.
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Analysis Mask
The area of interest for this project was
constrained to privately owned lands,
and excluded public ownerships, urban
or highly developed areas and lakes. To
“mask” out the exclusions, we used the
Minnesota Gap stewardship layer to
Federal, State, County and Large Private
Industrial lands. We then used the Gap
Land Cover layer to select all lands
classified as “Open Water” or
“Developed”. All of these values were
added to the mask colored in grey at
the right. The yellow values depict the
analysis area and grey values depict
areas excluded from the analysis.
Stewardship Plans
Until the beginning of this project, stewardship plans were kept as paper records
in local Forestry offices across the state. In order to digitize stewardship plan
locations, plans were collected from individual offices and owner boundaries
were digitized. Stand specific boundaries were NOT digitized, as it was outside
the scope and resources of this project. In addition, each parcel boundary was
given a unique identification number. A Microsoft Access Database was created
to hold information about individual plans. A variety of information was
recorded, including forest cover type, prescriptions, and accomplishments. Plans
in the Access database are related to the GIS parcel boundary data layer through
the unique identification number.
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