Implementing plant evolution into a dynamic vegetation model and its impact on the Phanerozoic biosphere

Land plants are a major contributor towards global terrestrial biomass which influences atmospheric CO₂ and O₂ however the amplitude of their contribution has fluctuated throughout the Phanerozoic; partly due to the evolution of plant features and strategies. An extended rise of atmospheric O₂ over the Carboniferous and Permian coincides with the rise of large vascular plants which is thought to have increased organic carbon burial rates. Here, we present one of the first dynamic climate-biogeochemical-vegetation model that allows the assessment of how plant evolution may have played a key role in the rise of the Late Paleozoic oxygen level. We implement a simple rooting evolution parameter and a high net primary productivity strategy of lycophyte paleotropical trees to the existing SCION-FLORA model. The evolution of roots amplifies continental weathering processes and increases overall biomass while the lycophyte tree strategy allows for accelerated biomass accumulation. The two strategies contribute towards the increase of organic carbon burial which leads to a rise in oxygen with lycophyte tree forests playing a much greater role. Without the evolution of lycophyte tree forests, Paleozoic O₂ levels cannot be reached suggesting that a quicker accumulation of biomass compared to present day forests was essential.