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Minimum levels of atmospheric oxygen from fossil tree roots imply new plant−oxygen feedback
Author(s) -
Sønderholm Fredrik,
Bjerrum Christian J.
Publication year - 2021
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/gbi.12435
Subject(s) - environmental science , terrestrial plant , atmospheric oxygen , oxygen , atmospheric sciences , root system , carbon cycle , botany , ecology , environmental chemistry , ecosystem , geology , chemistry , biology , organic chemistry
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 CO 2 and O 2 . Land plants are, however, themselves dependent on O 2 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 O 2 relevant for the geobiological community: (a) fossil root systems can be used as a proxy for minimum levels of past atmospheric O 2 consistent with a given fossil root depth; and (b) by identifying a positive feedback mechanism involving atmospheric O 2 , 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 O 2 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.