You must have never delved too much into science then. There are certain claims that have been well established for so long that citations are no longer needed. For example, we don't need citations to state the order of colours in a rainbow. Likewise, I don't need a citation to state that plant biomass increases with a greater concentration of CO2. That's basic science, it's unequivocal and not controversial. On the other hand, the previous dude made wild speculation about increased CO2 causing increased soil depletion. I'm sorry if you don't see the difference. Not everyone is suited to being a scientist.