Darwinian soil evolution: A review

Abstract

Soils diversified through geological time with the evolution life on land, from microbes in Archean soils, to fungi and amoebozoa in early Proterozoic soils, and lichens in late Proterozoic soils. Ordovician non-vascular land plants lived in Entisols and Aridisols, but trees created clayey subsurface horizons of Alfisols and Ultisols, and ferruginous horizons of Spodosols. Finally, sod grasslands creating distinctive surface horizons of Mollisols. Organisms can be adapted to particular environments, but also adapted by natural selection to other organisms in coevolutionary pairs, such as grasses and grazers, or trees and termites. Coevolution is notable for creating communities that can change the environment, such as ice ages brought on by evolution of forests and of grasslands. If life can be defined as a system capable of Darwinian evolution by natural selection, the same can also be said of soils. Even before the evolution of life, clay formation in soils that were like carbonaceous chondrite meteorites would have maintained a place in the sun and rain for the formation of more clay. Soils at matric potential for water were like multicellular creatures with tiny reactive centers within menisci of water between grains. They would have been a starter system for entirely organic-based life capable of natural selection with the same aim: hold the ground against erosion.