Fig. 3: Summary of plant evolution and evolving atmospheric composition versus age.

Atmospheric pCO₂ constraints from 410–380 Ma lycophytes (Asteroxylon, Baragwanathia, and Drepanophycus) with errorbars smaller than the size of the circles. Paired stomata and isotope data from the same locality are highlighted with black circles. Atmospheric pO₂ is constrained by charcoal evidence for wildfire since ~423 Ma^{54, 55} (red horizontal line) and fossil roots (red circles)⁵⁶ that sets minimum pO₂ levels according to controlled calibrations in the laboratory^{56, 84}. Modelled evolution of atmospheric pCO₂ (blue curve) and atmospheric pO₂ (red curve) derived by adjusting the COPSE Reloaded model for the coupled biogeochemical cycles such that continental weathering efficiency of early vegetated ecosystems scales with the physical weathering record of fines in terrestrial deposits⁴⁶ and outgassing from the Earth scales with continental arc volcanism. The ‘COPSE reloaded’ model are shown for comparison (thin, dashed curves)¹². For further details, see supplementary information. The emergence of land plants, vascular plants, arborescent plants with deep root systems and seed plants are shown with thin lines representing their origin by molecular clock estimates and thicker arrows representing fossil occurrences⁴⁵. Llan Llandovery, W Wenlock, L Ludlow, P Pridoli. The uncertainty of absolute age assignments are defined biostratigraphically, approximately ±1.5 Ma.