Examination of the Carbon Balance Hypothesis of Alpine Treeline Location in Glacier National Park, Montana

The mechanisms that determine the location of the upper altitudinal limit of tree species' survival are not completely understood. We test one hypothesis of treeline location, the carbon balance hypothesis, using a physiologically mechanistic forest process model to simulate carbon balance along elevational transects across the alpine treeline eco-tone in Glacier National Park, Montana. For 11-year time periods between 1954 and 1986, we find that predicted treeline elevation is not determined by carbon balance alone. Since there is not a strong link between carbon balances and treeline location, the coupling between climate and treeline location is not strong on a decadal scale. Therefore, the usefulness of the location of the alpine treeline ecotone in monitoring the effects of climatic change is questionable. [Key words: ecotone, carbon balance, treeline, Glacier National Park, Montana.]