Document: DOM-3-66-23

Potential impacts of global warming on western coniferous forests.

BACHELET, D.* ¹, R.P.NEILSON ^1,2, J.M.LENIHAN ¹ and R.J.DRAPEK ¹

Oregon State University, Corvallis, OR 97331 USA ¹
USDA Forest Service, Corvallis, OR 97331 USA ²

Abstract:
The fate of western coniferous forests under climate warming is uncertain because there is disagreement on 1) regional predictions from various global circulation models (increased summer temperatures with either little change in summer rainfall or increased summer rainfall) and 2) whether water use efficiency is enhanced as atmospheric CO₂ concentration increases. We used two vegetation models at 2 spatial resolutions (0.5 latitude/longitude and 10km) to look at potential scenarios of coniferous forests change in the 21st century. MAPSS, an equilibrium vegetation model, simulates little change in the coniferous forest area and a decrease in their LAI with low resolution climate data. However, it simulates an increase in their area and their LAI with high resolution climate data. Scaling errors can occur when climate scenarios are generated for the Western US because of its complex topography, consequently higher resolution data are more reliable. MC1, a dynamic vegetation model simulates the expansion of coniferous forests across the western states replacing taiga-tundra ecosystems displaced by warmer temperatures. We present results from two sets of runs : assuming 1) an increase in water use efficiency as CO₂ increases; 2) no increase in CO₂. Under the no CO₂ scenarios, MC1 predictions still hold while MAPSS predictions show increased water stress with increasing temperatures in the west.

Keywords: conifers,climate change,western U.S., MAPSS,MC1,biogeography,carbon

This abstract is being presented at: 3:30 PM in session:
CLIMATE CHANGE