Root responses along a subambient to elevated CO2 gradient in a C3–C4 grassland

Atmospheric CO2 (Ca) concentration has increased significantly during the last 20 000 years, and is projected to double this century. Despite the importance of belowground processes in the global carbon cycle, community-level and single species root responses to rising Ca are not well understood. We measured net community root biomass over 3 years using ingrowth cores in a natural C3–C4 grassland exposed to a gradient of Ca from preglacial to future levels (230–550 µmol mol-1)