Johnson et al. 2005

Johnson DL, Domier JEJ, Johnson DN. 2005. Reflections on the nature of soil and its biomantle. Annals of the Association of American Geographers 95: 11-31.

These authors advocate a new paradigm to underlie studies of soil science and related fields, based on increased recognition of processes occurring in and responsible for the production of the “biomantle”, the upper layer of soil composed of and formed by the actions of organisms. Many of these processes are based on movements of soil and soil components, and so are dominated by animals, especially active burrowers that are responsible for large vertical movements of soil in some environments. The biomantle is defined as being composed of “biofabric”, or materials that owe their existence to the actions of organisms, from the bodies of these organisms themselves, to the materials released by the organisms, to the minerals created by biological processes, to the voids created by their movements and the gases filling those voids released by their metabolisms.

These authors trace their ideas from the writings of Darwin, particularly his final work involving the activity of worms in “vegetable mould”, a late-18th century term for what we now call soil.
A biomantle layer, residing chiefly in the A horizon (or topsoil) can be more easily recognized in some landscapes than others. Humid tropical soils especially may show very thick and distinct biomantles, in two layers. The upper, thicker layer is composed of relatively fine materials, resting on a basal layer of coarser material; this basal layer is referred to here as the stonelayer. Below the stonelayer is non-biomantle, typically a B horizon (or subsoil). The hypothesized process creating this two-layer biomantle is the action of “conveyor belt” animals, especially termites that carry small particles upwards but are unable to move larger stones, thus eventually sorting the soil mineral material.

In other soils, such as loess-derived sandy soils without a large component of gravel and larger stones, such a two-layer biomantle may not form, or may be very weakly developed and difficult to identify as such. Nonetheless, bioturbation activity by burrowing animals is usually apparent, for example in the form of “krotovina”, in-filled animal burrows.

Besides advocating for a view of soils and their processes with an animal-based, biomantle point of view, these authors spend some time dismissing subaqueous soils (e.g. marine sediments) as simplistic, uncomplicated places lacking many of the key (and very complex) processes that occur in subaerial soils. Their list of such processes near the end of the paper, taken as a kind of justification for their uncited and unsupported dismissal of subaqueous soils, is composed entirely of those processes relating to changing water amounts in terrestrial soils, such as groundwater flow and wetting and drying events. I found their argument unconvincing, as they do not describe any aqueous-only processes such as changes in dissolved-O2 concentrations or the sorting action of water currents, and their blithe disregard for marine biodiversity in statements about how much more diverse the life in terrestrial soils must be, is the proverbial icing on the insult cake. Johnson et al.: please cite some evidence to support such sweeping generalizations.