The appearance and subsequent evolution of land plants is among the most important events in the earth system. Plant resulted in a change of earth surface albedo and the hydrological cycle, as well as increased rock weatherability thereby causing a persistent change in atmospheric CO₂ and O₂. Land plants are, however, themselves dependent on O₂ for respiration and long‐term survival, something not considered in current geochemical models. In this perspective, we highlight two aspects of land plants’ dependency on O₂ relevant for the geobiological community: (a) fossil root systems can be used as a proxy for minimum levels of past atmospheric O₂ consistent with a given fossil root depth; and (b) by identifying a positive feedback mechanism involving atmospheric O₂, root intensity, terrestrial primary production and organic carbon burial. As an example, we consider archaeopterid fossil root systems, resembling those of modern mature conifers. Our soil–plant model suggest that atmospheric O₂ with 1 SD probably reached pressures of 18.2 ± 1.9 kPa and 16.8 ± 2.1 kPa by the Middle and Late Devonian, respectively, that is 86 ± 9% and 79 ± 10% of the present‐day 21.2 kPa.

中文翻译：

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化石树根中最低水平的大气氧含量暗示着新的植物氧反馈

陆地植物的出现和随后的进化是地球系统中最重要的事件之一。植物导致地球表面反照率和水文循环的变化，以及岩石耐候性的提高，从而导致大气中CO ₂和O ₂的持续变化。然而，陆地植物自身依赖于O ₂进行呼吸和长期存活，这是当前地球化学模型中未考虑到的。从这个角度出发，我们着重指出了陆地植物对与地球生物群落有关的O ₂依赖性：（a）化石根系可以用作过去大气O ₂最低水平的替代物与给定的化石根深一致；（b）确定涉及大气O ₂，根系强度，陆地初级生产和有机碳埋葬的正反馈机制。例如，我们考虑了始翅类化石的根系，类似于现代成熟的针叶树。我们的土壤-植物模型表明，泥盆纪中晚期，大气中具有1  SD的O ₂可能分别达到了18.2±1.9 kPa和16.8±2.1 kPa的压力，分别为目前的86±9％和79±10％。日21.2 kPa。