PARENT SESSION
Oral Session #55: Fire Ecology. Presiding: M. Moritz.
Wednesday, August 8, 2001. 1:00 PM to 5:00 PM. Hall of Ideas H.
Climate determinants of fire regimes in the Greater Yellowstone Ecosystem.
Littell, Jeremy1,2, Graumlich, Lisa1,2, 1 2
ABSTRACT- Several decades of research describing pre-settlement fire regimes in western North American forests have demonstrated that fire, or its absence, is a strong determinant of ecological structure. A fundamental challenge in restoring fire in the West is to rely less on whether we have exceeded the natural range of forest structural variability and more on whether the structures we observe are compatible with fire regimes conditioned by current climate and future trends. Fire history research in the Greater Yellowstone Ecosystem has largely focused on describing fire-return intervals prior to European settlement. Very little research has attempted to link biophysical drivers and fire regimes in lower elevation (<2500m) forests. Using dendrochronology to date fire scars and stand ages, we assembled fire histories for Douglas-fir (Pseudotsuga menziesii) forests and related these fire regimes to past climate. Over the last 500 years, low elevation forests had relatively high fire frequency (20-50 years) and fires tended toward lower intensity, non-stand replacing fires. Moreover, the frequency of these fires is related to regional climate anomalies. Thus, a century of fire suppression has had a far more dramatic effect on the structure of lower-elevation forests than on subalpine forests. Successful efforts to restore ecosystem structure and process must meld concepts related to "natural range of variability" with biophysical (i.e., climate) and social (i.e., land use) constraints.
KEY WORDS: Fire ecology, Climate change, Greater Yellowstone Ecosystem, Natural range of variability