PARENT SESSION
Organized Oral Session 34: Incorporating ecological processes at many scales into biogeochemical and global climate change models
Organizer(s): WM Post, JS Olson, and C Peng
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 510b, Level 5, Palais des congrès de Montréal
Interactions among drought, fire, infestation, fire suppression and climate variability as revealed by a Dynamic General Vegetation Model, MC1.
Neilson, Ronald*,1, Lenihan, James1, Bachelet, Dominique2, Drapek, Raymond1, 1 USDA Forest Service, Corvallis, Oregon, USA2 Oregon State University, Corvallis, Oregon, USA
ABSTRACT- The MC1 dynamic general vegetation model (DGVM) is a hybrid between the MAPSS biogeography model and the CENTURY biogeochemical cycling model. A process-based fire model was also included using the best available ground and canopy fire algorithms and is fully integrated with feedbacks into the other two components of the model. The fire model determines what, when and how much to burn and imparts those impacts back to the simulated ecosystem. Ignition is triggered by meeting three threshold factors based on climate and simulated fuel conditions, since lightning and human ignition cannot as yet be adequately simulated. Simulations of the past 100 years over the conterminous U.S. demonstrate a close interaction between fire, climate and fuel condition. Patterns of interdecadal variability in the Pacific, Arctic and Atlantic oceans appear to entrain interdecadal patterns of fire area burned in the U.S., indicating that recent high-fire years were largely caused by climate variability. However, simulations including fire suppression reveal deeper layers of synergism between climate, fire and human interference. Fire suppression has interacted with fortuitous ocean-climate regime shifts to allow significant carbon sequestration into U.S. terrestrial ecosystems, much of it going into western woody expansion. However, the lack of fire has also allowed interior dry ecosystems to reach their water-limited carrying capacity during wet periods, rendering them unusually susceptible to drought-induced dieback during dry periods, followed by insect infestation. The relationship between fire and climate has also apparently varied through time, depending, in part, on the relative dominance between interannual and interdecadal climate variability patterns. These interactions have implications for ecosystem management with respect to carbon sequestration, fire suppression and risk reduction from catastrophic disturbances.
Key words: disturbance, wildfire, drought, simulation