Effects of Ant (Formica subsericea) Bioturbation On Soil Physical and Hydrological Properties.

The majority of ant-related bioturbation research has focused on physiochemical properties of the nest mound. Ants are also known, however, to line subsurface nest components (chambers and tunnels) with coarse material and backfill portions of the nest with excavated material.  This redistribution of material within the nest may contribute to alterations in soil physical and hydrological properties. Our objectives in this study were to measure both mound and subsurface soil properties focused near individual subsurface nest components and the surrounding soils. We sampled soils at different depths, directions, and distances from the nest center to provide an image of how ants affect bulk density, total carbon content, and particle-size distributions of soils within 1 m of their nests. Two Formica subsericea colonies were cast and excavated. Sets of ~1 cm³soil samples near nests were taken at depths corresponding to three morphological horizons (A, Bt, and Btss horizons) at four directions (90º, 180º, 270 º, and 360º), and at increasing distances from chambers or tunnels near the nest center (5 samples per layer per direction, ≤1 m away). A total of 120 unique samples from these two nests were analyzed for particle size distribution, total organic carbon content, and bulk density. Results from these analyses and their hydrological significance will be discussed.