The forest’s nutrient cycle drives its carbon cycle
Christian Körner
Abstract
This scientific commentary refers to ‘Forest stand and canopy development unaltered by 12 years of CO2 enrichment’ by Norby et al. (doi: 10.1093/treephys/tpab107). All life requires a balanced presence of c. 18 essential chemical elements other than carbon (C), hydrogen and oxygen (out of c. 94 natural elements on Earth). These rules of stoichiometry apply to bacteria and elephants, as much as to daisies and giant sequoias. Thus, in the longer run, plants can only incorporate additional C to the extent they can incorporate proportional amounts of all other elements essential for life. Given that plants always compete heavily for soil nutrients, these various nutrient cycles drive growth, and thus, the C cycle. Growth processes (meristematic activity and cell differentiation) control photosynthesis (A) by C demand (Körner 2015). Unless there are additional, freely available soil nutrients (not just nitrogen, N), elevated CO2 concentrations cannot...