Post #2417910

Yeah idk. I’m pretty skeptical. A few notes mostly just for myself… The main citation for the finding takes you to this paper: pmc.ncbi.nlm.nih.gov/articles/PMC4810679/ Which describes their experimental methodology which was basically a chamber based approach to compare what they are calling “ambient” to what they are calling elevated levels of CO~2~. They are calling “ambient” ~350ppm, and elevated ~550 ppm, and under these conditions, they see a difference in nutrient content, at least among c4 plants. Which is fine… and probably to be expected considering their evolutionary history… red line is when c4 plants evolved, c4 plants evolved in an era of extremely low atmospheric CO~2, and so they evolved some patches to deal with the CO~2~ concentration issue. But the issue I take is that their, laboratory conditions for “ambient” CO~2~ versus field CO~2~… they don’t reflect reality in fields where you have decomposing material in the soil, and plants actively growing and respiring. That would typically already be in their elevated range of 400-550, heck even 600 ppm, if its a well irrigated high carbon system. And yes it drops during the day while active photosynthesis is happening but really only down to their “ambient” range (maybe 325-375 ppm). There is just a lot of decomposition and other kinds of respiration happening where crops are actually grown.