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 behaviors at the surface, and physiochemical measurements are only taken from sediment in the mound. The impact of ants on soils below the surface is poorly understood and has not been well studied. Neoichnological experiments conducted at the University of Kansas have focused specifically on documenting subsurface behaviors and sediment mixing patterns of ants. These experiments have captured undocumented and important information on the excavation behaviors that show 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 into smaller ones. Another experiment documented the 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 tunnels and chambers no longer being used. In yet another experiment, ants were observed secreting salvia, which was used like an adhesive to line the walls of major nest passageways. They also used coordinated sweeping behaviors to level the floors of tunnels and chambers. When considering the observed behaviors and mixing patterns in these experiments, previous surface investigations lacked this crucial information. Observed ant behaviors from below the surface have a direct physical and chemical impact on soils. Additionally, the observed mixing patterns suggests that ants actually mix much more sediment than previously thought, and in some landscapes may have a larger biogenic imprint on soil mixing than earthworms.