Soil health, soil genetic horizons and biodiversity#.

Maintaining or recovering soil health is becoming a goal of many policies carried out at national, continental and global scales to promote global health. This viewpoint is aimed at stressing the relevance of a holistic approach to soil health assessment and monitoring, which is not only related to soil functional biodiversity but also considers the genetic horizons of the soil profile and not just the topsoil. We highlight that soil health has different connotations depending on the environmental setting and may show high spatial and temporal dynamics. Although the biological activity is often concentrated in the surficial horizon, we report increasing evidence that deep soil horizons host relevant biological communities, which are regulated by soil conditions that are usually different from those present in the topsoil. The processes responsible for the formation of surface and subsurface soil genetic horizons produce soil features that select the presence of organisms. The natural self‐organization of soil features is at the basis of the soil classification systems and of their ability to differentiate soil taxa and appreciate pedodiversity. Examples are reported of surface and deep soil genetic horizons as an important interpretative tool of soil functional biodiversity and soil health. Therefore, the assessing and monitoring of soil health should not be carried out at fixed depth, but according to soil genetic horizons. We conclude that the loss of the natural self‐organization of genetic horizons is a form of soil health degradation. [ABSTRACT FROM AUTHOR]