Supplemental Material Captions
SM 1(Supplemental Material 1).Supplementary material 1 provides more information regarding the methods for temporally downscaling the GCM data from monthly to daily data to accommodate Biome-BGC. In addition, more information about the process for estimating the extent of photosynthetic pathways and lifeforms is given. Finally a discussion of the Biome-BGC model is provided.
SM 2(Supplemental Material 2).Cursory overview of assumptions in the IPCC scenarios used to drive greenhouse gas emission patterns and subsequent estimates of future climates based on GCM results.
SM 3(Supplemental Material 3). False color composite depicting fractional abundance of C3, C4 photosynthetic pathways based on analysis of species composition for six assessment regions. The stippled (dotted) region is outside the study area and was not used at all during the study. The cross hatched regions represent areas outside the dryland extent and were only used for comparing projected NPP results with remotely sensed estimates of NPP across the same region. This was done because some areas, while tree dominated, have inclusions of non-forest vegetation such as balds, poccosin, and heathlands. The rangeland areas identified by Reeves and Mitchell (2011) used in the present study correspond to the definition offered by the U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS) as “A land cover/use category that includes land on which the climax or potential plant cover is composed principally of native grasses, grass-like plants, forbs or shrubs suitable for grazing and browsing, and introduced forage species that are managed like rangeland. This would include areas where introduced hardy and persistent grasses, such as crested wheatgrass, are planted and practices such as deferred grazing, burning, chaining, and rotational grazing, are used with little or no chemicals/fertilizer being applied. Grasslands, savannas, many wetlands, some deserts, and tundra are considered to be rangeland. Certain low forb and shrub communities, such as mesquite, chaparral, mountain shrub, and pinyon-juniper, are also included as rangeland. (NRCS 2007)”.
SM 4(Supplemental Material 4). Projected NOx (a) and CO2 (b) concentrations for the A1B, A2, and B2 emissions scenarios. In brackets is a suggested crosswalk between the AR4 scenarios and AR5 RCP’s (Moss et al. 2010; Rogelj et al. 2012) based on similarities in CO2 concentration by 2100.
SM 5 (Supplemental Material 5).Scenario and GCM combinations for which future climate projections were developed by Coulson et al. (2010a, 2010b). X’s denote a combination that was used, while the dash (–) indicates no data were available. Climatological data produced by Coulson et al.(2010a, 2010b) used in this study included precipitation (mm), and annual maximum and minimum temperature (°C). Estimates of vapor pressure deficit (Mpa), daylength (minutes), and solar radiation (W m-2) were created using data from Coulson et al.(2010a, 2010b) with MT-CLIM (Kimball 1997).
SM 6 (Supplemental Material 6). Temporal trajectories ofrelative change in NPP for U.S. rangelands from the baseline period (2001–2010) in six assessment regions from 2001 to 2100. Error bars represent SD about the mean of NPP estimated for all three emission scenarios.
SM 7(Supplemental Material 7). Comparison between NPP derived from Biome-BGC versus NPP estimated from the MODIS sensor for assessment regions between 2000 and 2012. The relationship between NPP in all 10 regions and the 6 main rangeland regions and MODIS-derived NPP are both shown.