Change in the fraction of total live vegetation carbon held in herbaceous plants between 1971-2000 and 2070-2099, as simulated by MC1 under Hadley A2 for the Apache-Sitgreaves study area, Arizona, USA

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 fraction of total live vegetation carbon held in herbaceous plants for the respective 30-year periods increased in some of the 5,311 grid cells of the Apache-Sitgreaves study area and decreased in others.The range of data values is from -0.817 to +0.999.  The mean value is +0.210.  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.