Technical Abstract: Barring further anthropogenic degradation of remaining habitats, Sandhills type longleaf forests should perform well in a future higher CO2 world. These data indicate that Pinus palustris and Aristida stricta would remain keystone species in future longleaf forests. Productivity of longleaf pine forests will likely be enhanced by rising levels of atmospheric CO2, although community structure may be altered. The ability of longleaf pine ecosystems to sequester carbon will likely increase as CO2 rises. Increases in allocation to woody biomass and increases in belowground allocation of C will enhance the C sequestration capabilities of these longleaf ecosystems. The pyric characteristics of this fire-dependent ecosystem should also be well-maintained. Caution should be used, however, when making broad ecosystem-scale predictions from this experiment. Small understory species did not perform well in CO2-enriched portions of our model ecosystem. If species diversity is reduced in these communities, then total ecosystems response to elevated CO2 may be reduced. Frequently burned Sandhills savannahs typically have > 40 species ha-1 that represent a variety of growth forms, hence it is impossible to make accurate predictions for each species. However, longleaf ecosystems harbor a large number of threatened and endangered species and their current tenuous position in these communities may become more imperiled if these species cannot maintain or improve their competitive abilities as atmospheric CO2 continues to rise.