Postglacial Forests of the Glacier National Park Region

Abstract

Sphagnumi bogs are not comm-inon in the northern Rocky Mountain region of the United States, and many that do exist are more or less inaccessible with a reasonable amount of time and effort. The writer was fortunate to locate two bogs in Glacier National Park whose sections reveal excellent pollen profiles from which the postglacial forest succession has been reconstructed and the climatic sequence interpreted. These organic sediments have accumulated in Johns and Fish Lakes, both. of which lie about one mile east of the north end of McDonald Lake near the southwest boundary of the Park. Johns Lake lies at an elevation of about 3300 feet. and Fish Lake has an altitude of about 4100 feet and is located about two and one-half miles due south of the former. Both are less than five miles west of the Continental Divide which rises to an elevation of about 8000 feet in this area. The sites of both lakes were overriden by the McDonald Valley glacier which probably was of Late Wisconsin age. McDonald Lake drains into the Middle Fork of the Flathead River which coalesces with the North and South Forks to form the Flathead River which empties into Flathead Lake south of the Park. Johns Lake covers about 5 acres and is bordered by a sphagnum-sedge mat from 10 to 25 feet wide. Typical plants growing on the mat are Drosera xrotmiidifolia L., Potentilla palustris L., Dulichium arundinaceumn (L.) Pritt., Kainia poli-