Fire and climate history of western Montana

Centennial Valley, southwestern MontanaA ca. 20,000-yr-old sediment core from Lower Red Rock Lake in the Centennial Valley of southwest Montana was obtained to reconstruct the vegetation, climate, and environmental changes during and following the late-Pinedale Glaciation. Examination of the first arrival of Pseudotsuga in pollen records throughout the region shows that its arrival was later at sites on the Atlantic side of the Continental Divide as compared to sites on the Pacific side. The geographic pattern suggests that the Continental Divide posed a topographic or climate barrier in the late-glacial period, delaying the migration of Pseudotsuga menziesii from glacial refugia.