Comment On "Unexpected Reversal Of C-3 Versus C-4 Grass Response To Elevated Co2 During A 20-Year Field Experiment"

Reich et al. (Reports, 20 April 2018, p. 317) assert that the responses of C-3 and C-4 grass biomass to elevated CO2 "challenge the current C-3-C-4 [elevated CO2] paradigm," but these responses can be explained by the natural history of the experimental plants and soils without challenging this paradigm.