Montane and subalpine plants of the Sweetgrass Hills, Montana, and their relation to early postglacial environments of the northern Great Plains

Abstract

Relict montane and subalpine plant communities of the Sweetgrass Hills, a small, isolated mountain range in the northern Great Plains, are described.Although the montane forests occupy an extremely small area (less than 20 km2), they are surprisingly rich in coniferous tree species, as they have representatives of seven taxa (including one hybrid).This is evidence that a montane coniferous forest belt, in addition to a boreal forest belt, followed the retreating Laurentide ice sheet as it left the area at the close of the Wisconsin glaciation.A lack of typical subalpine understory species indicates a shift to a climate no longer favoring the relict subalpine forest communities.