The burial of organic carbon as affected by the evolution of land plants

It is hypothesized that, over Phanerozoic time, the terrigenous organic carbon (_orgC) pool became increasingly susceptible to biological decay through (a) reduction in the ratio of phenolic‐rich periderm to total biomass and (b) decline in the extent of lignification in foliage and other plant organs. Fungal evolution, meanwhile, resulted in greater abundance and higher activity levels of lignin‐degrading organisms, and faster turnover of refractory _orgC. The result was reduced burial of _orgC, which, in turn, checked the accumulation of O₂ in the atmosphere and buffered the global redox balance against variation in biomass production by land plants. Feedback from O₂ level to fungal metabolism of lignin further stabilized the system. Thus, the relatively small Paleozoic land biota could have caused much greater perturbations of redox balance than were caused by the much larger and more productive land biotas of the Tertiary.