Technical Comments

Comment on “Unexpected reversal of C3 versus C4 grass response to elevated CO2 during a 20-year field experiment”

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Science  31 Aug 2018:
Vol. 361, Issue 6405, eaau3016
DOI: 10.1126/science.aau3016

Figures

  • Fig. 1 Relationships between the CO2 effect on total C4-C3 biomass and growing-season climate.

    The biomass data are from the measurements of Reich et al. (1). CO2 effect size = biomass under eCO2 condition – biomass under ambient CO2 condition. The Cedar Creek weather data are from Fort Snelling near the Saint Paul International Airport (www.wunderground.com/history/airport/KMSP). The biomass and weather data are shown as 3-yr moving averages centered over the middle of each 3-yr group. The relationships between CO2 effect size and climatic factors were analyzed using generalized linear models (CO2 effect size – temperature + rainfall; family = Gaussian; link = identity). The partial R2 of each climatic factor was obtained using the rsq. partial function with the rsq package in the R version 3.2.2.

  • Fig. 2 Inter-annual trajectories of C4 total biomass at the ambient (red) and elevated CO2 (blue) levels and summer rainfall (orange).

    The Biomass data from the measurements of Reich et al. (1) are shown as 3-yr moving averages centered over the middle of each 3-yr group. The Cedar Creek weather data are from Fort Snelling near the Saint Paul International Airport.

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