Forest Volume and Species Distribution Maps
The following maps provide relative amounts and distribution of forest land volume and tree species located within the assigned survey area of the Northern Research Station Forest Inventory and Analysis (FIA) Unit. The map construction method is simple, consisting of estimating the volume, numbers of trees, or basal area of trees using forested FIA plots within a 30 km radius circle. Each estimate is placed at the map location of the circle. The circle is moved systematically over the geographic area of 24 states within the NRS FIA region, “painting” estimates of forest information on the map as it goes.
Forest estimates are calculated on a per acre of forest land basis.Therefore, all the forest information is located only in the area of the map labeled as forest land. The FIA program has a fairly precise “forest land” definition, see www.fia.fs.fed.us. There are many trees on the non-forested land depicted by the map, but those areas are not included in the mapped tree estimates. Using classification tree modeling methods, the FIA program produced a forest mask by modeling the binary variable of forest vs. nonforest as a function of many predictor variables. The resulting forest/non-forest map was produced at an original resolution of 250 meters (Blackard et al. 2006). It is used in these maps as the layer which decides what is forested on the regional map.
The maps are intended for qualitative regional forest evaluation
and study. Small area analysis is not advisable, since the geographic
unit of information is about 700,000 acres (33 miles square) in size.
Furthermore, the estimates are based on the FIA definition of “forest
land” not tree covered land, such as often found in an urban area.
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Last Modified: 05/18/2011