This
map represents the change between 1971-2000 and 2070-2099 in the annual peak
fraction of total live vegetation carbon held in herbaceous plants, as
simulated by the model MC1 under the Hadley future climate projection and
A2 anthropogenic emissions scenario. The average change in the fraction of total live vegetation held in herbaceous plants for the respective 30-year periods
decreased in some of the 5,311 grid cells of the Eastern Oregon study area and increased in others. The range of data values is from -0.600 to
+0.991. The mean value is +0.188. Data values are calculated as
GFRAC(2070-2099) minus GFRAC(1971-2000). GFRAC data is from MC1 version
B60.
The vegetation model MC1 (e.g. Bachelet et al. 2001) was
used to simulate vegetation dynamics, associated carbon and nitrogen cycle,
water budget, and wild fire impacts at two study sites, one in eastern Oregon
(Deschutes and Fremont-Winema National Forests) and one in Arizona
(Apache-Sitgreaves National Forest area). The work was funded by the USDA
Forest Service (PNW 09-JV-11261900-003). Historical climate input data used to
run the model were provided by the PRISM group (Chris Daly, OSU) at 30
arc-second (~800m) spatial grain. The model was also run using future climate
change projections from three general circulation models: Hadley, CSIRO Mk3 and
MIROC 3.2 medres. Future climate datasets were generated through statistical
downscaling from general circulation model output using a simple anomaly method
and the climatology (1971-2000) from the PRISM group at 30 arc-second spatial
grain. The model was run assuming that nitrogen demand from plants is
always met, so that the nitrogen concentrations in various plant parts never
drop below their minimum reported values. A CO2 enhancement effect increases
productivity and water use efficiency as atmospheric CO2 concentration
increases.