Techno-moder: A proposal for a new morpho-functional humus form developing on Technosols revealed by micromorphology

[Display omitted] •Micromorphology of Technosols’ humipedons was studied on a former coking plant area.•A new humus form had developed on the highly anthropized area.•The term “techno-moder” is proposed to classify this new humus form.•Faunal feces were accumulated on a technogenic horizons in absence of earthworms.•Humipedon characteristics could be considered as footprints of anthropic activity. Human impact on soil systems is now widely acknowledged. “Technosols” appeared in soil classification only a decade ago and the notion of “techno humus system” has emerged even more recently. Yet the variety of humus forms that could develop on Technosol remains largely unknown. To contribute to filling this knowledge gap, we studied the humus form developing on two Technosols resulting from the activity of a former coking plant and compared it with one developed on a Cambisol as a reference for the area. We used field description and micromorphology on thin sections coupled with a point-and-count method to precisely describe the surface of the humipedons of the area studied. A total of 13,841 counts and identifications were performed on 11 thin sections and spread into 17 fabric units. Micromorphology on thin soil sections revealed that epi-saprophagous organisms transformed most of the neo-formed organic matter on the Technosols studied, leading to an accumulation of feces on the surface of the humipedon. Our results suggested that the humus form developing on the Technosols was similar to a moder and exhibited the same ectorganic horizons (OL, OF, zOH), whilst overlaying a technogenic one composed mostly of coal fragments. We would like to propose the term “techno-moder” for this new humus form, developing in the absence of an A horizon. On the other hand, micromorphology allowed us to classify the humus form developed on the Cambisol as a eumull containing anthropic coal by-products. Specification of the humus form developing on such soils could represent a promising way to specify pedological processes such as organic matter decomposition, soil aggregation and also to enrich the humus form classification on Technosols.