Formicarious Pedons, the Initial Effect of Mound-Building Ants on Soils

Abstract

The activity of mound‐building ants results in the production of a pedon which is profoundly different from its uninhabited counterpart in structure, composition, behavior, genesis, and pedogenic regime. The formicarious pedon is offered as a theoretical construct to organize the body of knowledge regarding the effects of ants on soils and to represent the initial effects of mound‐building ants on soils. Formicarious pedons are characterized by a large mound overlying the original pedon. This mound often has a crusted or mulched exterior and a highly porous interior. The interior of the mound, as well as the soil below the mound is riddled with channels and chambers created by the ants. The mound consists of surface and subsoil material and differs from the surrounding soil in texture, structure, and chemistry. This leads to a different pedogenetic environment. The process of mound‐nest construction is the dominant soil‐forming process operating within the formicarious pedon. As colonies relocate through time, the effects of the ants can be applied to entire landscapes.

Mesolithic hearth-pits: fact or fantasy? A reassessment based on the evidence from the sites of Doel and Verrebroek (Belgium)

“…During a survey in an oak forest at Holtkrat, in the centre of Jutland (Denmark), about 50 active and 50 abandoned nests of this type were detected in an area of 4 ha. This corresponds to one ant nest within an average distance of 20 m. Similar figures were obtained in other studies (for an overview see Green et al, 1998: Table 1). During a prospection in the same forest we personally observed an ant dome associated with a coppiced lime (Tilia sp.)…”

“…In a review paper on "formicarious pedons", Green et al (1998) pay attention to the mound-building ants and their initial impact on soil morphology. A large diversity of above-and underground nest morphology and composition appears to be a function of vegetation composition, soil type and ant species.…”

“…All this burrowing affects the structure and original horizonation of the soil. Most of the ant mounds discussed in Green et al (1998) are largely composed of mineral earth mixed with plant fragments, a mound type frequently observed in grasslands. Mounds dominantly composed of organic debris, mixed with some mineral material are observed in areas of both deciduous and coniferous forests and sometimes on heathlands with sandy soils (Figs.…”

“…This explains the high content of organic matter. Inorganic constituents like Ca, Mg, K and particularly P are commonly related to such a nutrient enrichment (Frouz et al, 2005;Green et al, 1998;. Evidently the burning of wood, which would fit with the hearth-pit hypothesis, also liberates a certain amount of these mineral elements in variable proportions according to the type of fuel, (e.g.…”

“…an organic matter rich surface horizon in which plants grow) by earthworms (Darwin, 1881). In Doel this process can very well be explained by the presence of mound-building ants creating formicarious pedons (Green et al, 1998). In fact Darwin also suggested that other organisms than earthworms, like ants, could produce a collapse of the soil surface and the development of a vegetable mould.…”