PARENT SESSION
Contributed Oral Session 157: Climate Dynamics: Temperature Effects; Modeling
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 516 D, Level 5, Palais des congrès de Montréal
Implications of migration limitation for global warming-induced changes in north temperate tree communities.
Malcolm, Jay*,1, Puric-Mladenovic, Danijela1, Shi, Hua1, 1 University of Toronto, Toronto, ON, Canada
ABSTRACT- Previous research suggests that global warming may require species to migrate at rates faster than even those observed during the recent glaciation; however, direct calculation of future migration rates based on modelled shifts in individual species ranges has not been undertaken. Here, we use regression trees to model ranges of 134 tree species in eastern North America under recent (1975) and future (2095) climates, and, for each species, to calculate presumptive future migration rates. In addition, we examine the potential effects of migration limitation on species richness and forest composition by contrasting a scenario of perfect migration against one in which maximum migration is limited to historically high migration rates (1 km/yr). Data on current species distributions were from the U.S. Forest Service, Ontario's Forest Resource Inventory, and c. 4,700 field plots in Ontario. Predictor variables included information on current climate, soil, topography, and land cover at 300-arcsec resolution. Future climate conditions were from three General Circulation Models (HADCM3, CGCM2, and CSIROMk2) for two IPCC emissions scenarios (A2 and B2). Nearly all species distributions showed marked shifts northward. The net effect was a large increase in tree species richness in Ontario, especially in the south where average richness more than doubled. The strong latitudinal shifts in species distributions were indicative of very high required migration rates in the Province, averaging >3 km/yr across all species, and with >65% of grid cells had average rates in excess of 1 km/yr. When migration was limited, the increase in species diversity was much lower; in the most severe climate scenarios, a decrease was observed. Under migration limitation, large areas of the Province became occupied by forest types that could not be classified using existing provincial classification systems and, in the most severe climate scenarios, large areas in the north became devoid of all currently dominant tree species. These results highlight the magnitude of the ecological change projected for Ontario and also the possibility that future forest composition and productivity in temperate areas will increasingly depend on the abilities of species to tolerate conditions outside of those in which they presently occur.
Key words: climate change, migration rates, tree communities, Ontario