Observations on subsurface behaviors and mixing patterns of ants

Ants are an important component of soil systems and their ability to move soil to the surface and mix soil nutrients has been well documented. More often than not, however, these studies only observe ant behavior at the surface, and physiochemical measurements are only taken from sediment in the mound. The impact of ants on soils below the surface has not been well documented. A series of neoichnological experiments conducted at the University of Kansas have focused specifically on documenting subsurface behaviors and mixing patterns of ants. These experiments have captured undocumented and important information on the excavation behaviors of ants and how sediment is mixed throughout the nest during construction and maintenance. In one experiment pushing and forcing behaviors were observed as ants constructed their nest. Cutting behaviors were also observed as ants physically cut larger soil particles. Another experiment documented the amount (volume) of sediment excavated by ants. While the nest mound contained large volumes of excavated sediment, the majority of all excavated sediment was placed back into the nest, through both advective and diffusive mixing. Another experiment documented the deliberate movement of plant material to the deepest parts of the nest where it was used to close passageways no longer being used. In yet another experiment, ants were observed secreting salvia, which was then used like concrete to line the walls of major nest passageways. When considering the observed behaviors and mixing patterns documented in these experiments, past surface investigations have lacked crucial information. Observed ant behaviors from below the surface have a direct physical and chemical impact on soils. Additionally, the mixing patterns observed suggest that ants actually mix much more sediment than previously observed, and in some landscapes may have a larger biogenic impact on soil mixing than earthworms.