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Effect of Elevated CO2 on the Root Mass Fraction of Plants
Wang, X. and Taub, D.R. 2010. Interactive effects of elevated carbon dioxide and environmental stresses on root mass fraction in plants: a meta-analytical synthesis using pairwise techniques. Oecologia 163: 1-11.

What was done
The authors conducted a series of meta-analyses that reveal how differences in the availability of soil fertility and water, as well as the stress of ozone (O3) pollution, affect the biomass allocation in plants -- as expressed by the change in the fraction of root mass to total biomass (i.e., root mass fraction or RMF) -- that occurs when plants are exposed to air enriched with CO2 to levels ranging anywhere from 500 to 1000 ppm. This they did based on data they extracted from 541 peer-reviewed scientific journal articles, which yielded them a total of 1,349 RMF observations.

What was learned
Wang and Taub determined that lower soil fertility increased RMF, and that the magnitude of the increase "was similar for ambient and elevated CO2-grown plants." They also found that lower soil water content increased RMF; but in this case they report that it did so "to a greater extent at elevated than at ambient CO2." Last of all, they discovered that "CO2 enrichment had little effect on the magnitude of O3-caused reduction in RMF in herbaceous species," but that "it alleviated the adverse effect of higher O3 on root production in woody species."

What it means
The two researchers conclude that "under abiotic stresses, e.g., drought and higher O3, elevated CO2-grown plants will likely increase biomass allocation below-ground," where it can be used to construct more roots that can be used to acquire more water and nutrients. However, "because of the non-uniform changes in drought and O3 projected for different parts of the world," they say that "elevated CO2 will have regional, but not global, effects on biomass allocation under various global change scenarios." And these responses should help earth's plants -- some regionally and some globally -- to better acquire more of the nutrients and water they will need to sustain the enhanced levels of growth that can be expected in a high-CO2 world of the future, even in the face of significant ozone pollution.

Reviewed 4 August 2010