| dc.description.abstract | The majority of ant-related bioturbation research has focused on physiochemical properties of the nest mound. However, ants are also known to line subsurface nest components (chambers and galleries) with coarse material, and may expand or backfill areas as colony size expands and contracts. These alterations may contribute to significant redistribution of soil material leading to alterations in soil physical and hydrological properties. The goal of this study was to examine the physical, chemical, and hydrological effects of the subterranean portion of ant nests on the soil profile. We measured soil in the field that was located near (<2 cm) and away (<1 m) from ant nests, and compared them to unaltered soil approximately 2 m away. Two-dimensional tracings of nest architecture were used to predict the nest effect on hydraulic properties of a fine-textured soil. In addition, we took approximately 1600 ant specimens from one of these nests and placed them into two formicaria with coarse-textured soil that approximated horizons in the field. Overall, the mound showed the largest differences from the original soil, having lower bulk density and higher total carbon than the rest of the nest. Ant-altered portions of soil extended laterally well beyond the surface mound in soils with vertic properties, whereas effects of ants on nest carbon were restricted to nest walls in coarse-textured soils. This difference was due to ants utilizing interpedal spaces of vertic soils that were open during dry years. Hydrologic properties calculated from cross-sectional photographs and tracings of the excavated nest showed that ant activity significantly increased the saturated hydraulic conductivity of the soil, and was associated with faster increases and decreases in moisture content. This preferential flow effect was present, but more muted in coarse textured soils with naturally high saturated conductivity. Regardless of soil type, the effects of ant altered soil diminish with increasing depth, as nest structures decrease in density and the soil becomes harder to excavate, especially during dry years. | |
