Biological View of Soil Evolution.

Soils are the crucible to terrestrial life and are the most complicated biomaterials on the planet. This paper explores the biological evolution of soils to provide an alternative view of global soil change and belowground biodiversity. We first investigate the “genotype” and “phenotype” of soils. Soil phenotype (i.e., various types of soils) is considered as a synergistic integration of soil genotype (i.e., basic functional units of soils) and surrounding external influences (e.g., soil environment and land use). The evolution process of organisms within soils ensures the plasticity property of soil phenotype in response to changes in the environment. Environmental stresses dominate the evolution direction of soil organisms, which trigger fast soil phenotype variation. Natural selection screens out soil organisms that adapt environment conditions and determine the trend of cumulative soil phenotype variation. The possibility of developing soil “phylogenetic tree” to quantify the inner relation between different soil types and to delineate the historical evolution scenarios of soils is then explored. This preliminary study of soil systems recognizes soil changes from a biological evolution point of view, suggesting profound anthropogenic impacts on soil phenotype and belowground biodiversity. Meanwhile, the resilience of soil systems to environmental changes also highlights the possible paths towards sustainable land use.