Planning for tree species migration with climate change is an immediate challenge for land managers. Climate change models suggest that lodgepole pine will decline in the northwestern United States by the end of the 21st century. As climate change transforms the lodgepole pine zone into a warmer, drier environment, drought-tolerant ponderosa pine may establish within the historic lodgepole pine range. Tree species migration is a complex process involving ecological linkages between belowground and aboveground ecosystems. Trees rely on symbiotic relationships with mycorrhizal fungi for optimal survival and growth. Successful migration of tree species may be constrained by the distribution or co-migration of belowground fungal symbionts. Forest Service scientists' finding of remarkable overlap in mycorrhizal fungi species colonizing ponderosa and lodgepole pines bodes well for the migration of ponderosa pine into the historic lodgepole pine range. Mycorrhizal networks provide conduits for nutrient exchange between tree species. In an assisted migration management approach, mycorrhizal fungal networks may enhance seedling survivorship and growth. This research advances the understanding of belowground ecosystems and the role of mycorrhizal fungi, particularly if an assisted migration is considered as a component of an adaptation management strategy. This information is useful to forest managers of pine ecosystems in eastern and central Oregon, Washington, Idaho, British Columbia, Spain, and other Mediterranean climates.