Effects of activities of ants (Camponotus japonicus) on soil moisture cannot be neglected in the northern Loess Plateau

Ants can create abundant and continuous soil macropores by burrowing their nests. The hydrological processes in ant nests for different soil types and the effects of ant activities on soil water evaporation are unclear. In this study, we assessed the effects of ant (Camponotus japonicus) nests on preferential flow in the loam and sand soils and on soil water evaporation. First, 12 plots in the sand and loam soils with and without ants were selected for the preferential flow measurements in the field. Second, 200 worker ants and the queen ant were introduced to abandoned cropland plots, and the comprehensive effects of ants on soil moisture down to 340 cm were measured using neutron probes. Third, at the Shenmu Erosion and Environment Research Station, 18 iron buckets (20 cm in diameter, 20 cm high) were filled with disturbed loam soil, and a different number of ants was used to assess the effects of ant activities on soil evaporation. The infiltration rate in areas with a nest was approximately 20 times higher than that in no-nest areas. Moreover, the dyeing depths in loam and sand soil with a nest were 47 ± 4.6 and 34 ± 1.5 cm, which were significantly greater than those without a nest (13 ± 2.7 and 23 ± 2.3 cm). Ant nests reached a depth of 60 cm in the field. The effects of a nest on soil moisture existed between 0 and 120 cm deep. Moreover, by moving a high number of “homemade soil aggregates” (1.6 ± 0.18 mm in diameter) onto the soil surface, ants reduced soil evaporation. Ant activities improved soil moisture around the nest by increasing rainfall infiltration and reducing soil water evaporation, which increased the variation in soil water distribution in the soil profile and may benefit the general restoration of vegetation on the Loess Plateau.