Modeled Current: map of current distribution, as modeled from the regression tree analysis, using the tree diagram.

 Geographic Predictors:  This map is tied to the tree diagram, and shows the main variables which drive the distribution of the species. Follow the branches of the tree diagram to the class number at the bottom of each node to match the legend for this map. This output is a main advantage to the regression tree analysis approach, as the map shows how different variables can drive the IV of a species at different parts of its range. See help on interpreting the diagram.

The gray shaded portions of the maps (No Data on legends) had no forest information available, due to one or more of the following: (1) there were no data recorded for any tree species for those counties (e.g., prairie states in the western part of the region), (2) one or more of the four FIA regions (northeastern, north central, southeast, southern) did not report the species in their data base because it was not present in the region (e.g., distinctly northern or southern species), and (3) one or more of the FIA regions do not recognize a particular species name as present in the unit, even though it undoubtably is present but called something else (e.g. taxonomic confusion like in the hickories (Carya sp.)).

Literature cited:
Little, E.L. 1971. Atlas of United States trees. Vol. 1. Conifers and important hardwoods. Misc. Publ. 1146. Washington,D.C.: U.S. Department of Agriculture, Forest Service. 9 p, 200 maps.

Little, E.L. 1977. Atlas of United States Trees. Vol. 4. Minor eastern hardwoods. Misc. Publ. 1342. Washington, D.C.: U.S. Department of Agriculture, Forest Service. 17 p, 230 maps.