Grassland Root Biomass Response to Atmospheric CO2 Enrichment
Anderson, L.J., Derner, J.D., Polley, H.W., Gordon, W.S., Eissenstat, D.M. and Jackson, R.B. 2010. Root responses along a subambient to elevated CO2 gradient in a C3-C4 grassland. Global Change Biology 16: 454-468.
Upon the conclusion of their study, Anderson et al. report that based on the linear relationship they derived from all twenty of the ingrowth biomass assessments they conducted, there was "a 40% increase in the ingrowth root biomass ratio from 380 to 480 ppm as compared with a 36% increase from 280 to 380 ppm," but they say that excluding one extremely variable data point, and using a power function they fit to the data, "the contrast is even greater: a 50% increase from 380 to 480 ppm vs. a 41% increase from 280 to 380 ppm." And we additionally note, in this regard, that in going from the linear relationship to the power function, the r2 value of the relationship jumped from 0.10 to 0.50, and that P dropped from 0.095 to less than 0.001.
Thus, the six scientists say "these data suggest that root biomass in grasslands may have changed markedly as atmospheric CO2 increased since the last glacial period, but that more substantial changes are ahead if the air's CO2 content doubles by the end of this century as predicted." And, these anticipated "changes" should all be positive, implying ever greater grassland root biomass -- and all that that phenomenon implies -- as the air's CO2 content continues to climb ever higher.