Tanana Flats Training Area (TFTA) occupies 653,746 acres of the Middle Tanana River Basin. The Tanana Flats supports a complex mosaic of ecosystems and is situated on a large alluvial fan and glacial outwash complex built out of the north side of the Alaska Range. Both surface and subsurface water move across the Tanana Flats on a very low gradient originating from mountain glaciers that discharge to the Tanana River. A portion of the groundwater surfaces in springs and diffuse upwellings contributing to an extensive system of fens. The Flats also include a variety of other habitats, such as forests of white spruce, paper birch, and quaking aspen; black spruce bogs; thickets of willow and alder; and grasslands and meadows.
Donnelly Training Area (DTA) occupies 650,000 acres of the middle Tanana River Basin. DTA supports a complex mosaic of ecosystems and is composed of many acres of wetlands, kettle lakes, alpine and tundra habitats. Parts of DTA were designated as an Important Bird Area of World significance by the International Union for Conservation of Nature (IUCN) for the large numbers of trumpeter swans and sandhill cranes that use the area.
These habitats are important to a variety of songbirds, shorebirds, and upland game birds. Some of the more significant species known to utilize the area are: sandhill crane, trumpeter swans, Canada geese, American wigeon, green-winged teal, mallard, northern pintail, blue-winged teal, northern shoveler, and scaup (both lesser and greater). Other bird species known to use this area include; bald eagles, red-tailed hawks, northern harriers, short-eared owls, northern hawk owls, and numerous small passerine species including warblers, thrushes, blackbirds, and sparrows.