Minnesota Stewardship Spatial Analysis Project Methodology and Analysis documentation January 28, 2008

Transcription

1 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 WEIGHT % OF TOTAL 1. Private Forest Ownership Riparian Areas Forest Patch Size Wetlands Slope Impaired Watersheds Public Water Supplies Rare and Natural Features Risk of Forest Pests Proximity to Public Lands Risk of Development Risk of Fire TOTAL 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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3 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. 3

4 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. 4

5 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. 5

6 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. 6

7 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. 7

8 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 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. 8

9 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. 9