Potential Changes in the Distributions of Western North America Tree and Shrub Taxa under Future Climate Scenarios |
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Authors: | Sarah L Shafer Patrick J Bartlein Robert S Thompson |
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Institution: | (1) Department of Geography, University of Oregon, Eugene, Oregon 97403-1251, USA, US;(2) Earth Surface Processes Team, US Geological Survey, Box 25046, MS980, Denver Federal Center, Denver, Colorado 80225, USA, US |
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Abstract: | Increases in atmospheric greenhouse gases are driving significant changes in global climate. To project potential vegetation
response to future climate change, this study uses response surfaces to describe the relationship between bioclimatic variables
and the distribution of tree and shrub taxa in western North America. The response surfaces illustrate the probability of
the occurrence of a taxon at particular points in climate space. Climate space was defined using three bioclimatic variables:
mean temperature of the coldest month, growing degree days, and a moisture index. Species distributions were simulated under
present climate using observed data (1951–80, 30-year mean) and under future climate (2090–99, 10-year mean) using scenarios
generated by three general circulation models—HADCM2, CGCM1, and CSIRO. The scenarios assume a 1% per year compound increase
in greenhouse gases and changes in sulfate (SO4) aerosols based on the Intergovernmental Panel on Climate Change (IPCC) IS92a scenario. The results indicate that under future
climate conditions, potential range changes could be large for many tree and shrub taxa. Shifts in the potential ranges of
species are simulated to occur not only northward but in all directions, including southward of the existing ranges of certain
species. The simulated potential distributions of some species become increasingly fragmented under the future climate scenarios,
while the simulated potential distributions of other species expand. The magnitudes of the simulated range changes imply significant
impacts to ecosystems and shifts in patterns of species diversity in western North America.
Received 12 May 2000; accepted 20 December 2000. |
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Keywords: | : future climate change response surface models western North America trees |
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