Nest structure of ant Lasius neoniger Emery and its implications to soil modification

Abstract

The ant Lasius neoniger Emery is one of the most abundant ant species found in the temperate regions of North America and has been studied primarily from an entomological standpoint. This study was conducted to characterize its nest structure and implications to soil modification. To study the structure, development, and micromorphological characteristics of the ant nests, we constructed three-dimensional models of the nests from excavated nest castings made with dental gypsum and ant farms with Plexiglas, and made thin sections ( ≈30 μm thick) from undisturbed field soil samples that contained the nests. We assessed the effect of the ant on soil chemical properties by comparing the composition of ant crater rim and nest materials with that of associated bulk soil. The ant nests consisted of underground branched networks of galleries and chambers concentrated in the upper 0.3 m of the soil, with a few vertical galleries penetrating to about 0.7 m. The galleries tended to be circular tubes (channels) 1.5 to 5.0 mm in diameter, whereas the chambers, connected by the galleries, bulged to diameters of 10 to 20 mm and were 30 to 50 mm in length. The volume of the nests ranged from 20 to 250 cm 3. Walls of the nests ( ≈1 μm thick) were more consolidated and contained larger amounts of fine sand, silt, and colloidal material than adjoining bulk soil. The primary effect of the ants was mixing of the upper 0.7 m of soil. Estimated soil turnover time ranges, for upper 0.3 m soil, from approximately 1000 years for the grass border areas of a corn field to 2800 years inside the field. For soils between 0.3 and 0.7 m depths, estimated soil turnover time ranges from approximately 9000 years for the grass border areas to 24,000 years inside the corn field. Selective mining by ants of fine-particles, which concentrate in the upper tier of the soil, may also counter balance processes such as clay translocation and nutrient leaching that tend to degrade physical and chemical attributes of sandy soil surfaces forming in humid environment.