Characteristics of Soil Evaporation and Temperature under Aggregate Mulches Created by Burrowing Ants (Camponotus japonicus)

Mulch on the soil surface is an effective practice for conserving soil moisture. In this study, we assessed the effects of aggregate mulches created by burrowing ants (Camponotus japonicus) on soil evaporation and temperature. A series of simulation experiments were conducted using buckets (20 cm diameter x 20 cm height) filled with loess soil (7.3 kg). Seven ant populations (0, 10, 30, 50, 100, 150, and 200) and four mulch thicknesses (0 [bare soil], 3, 6, and 9 mm) were used to evaluate the effects of ant abundance and mulch thickness on soil evaporation rates and temperature. The evaporation rate and temperature were measured with an electronic scale (with 1 g precision) and electronic thermometers (with 0.1 degrees C precision). The number of aggregates was linearly correlated with the number of introduced ants (R-2 = 0.8927). A negative relationship existed between the soil evaporation rate and a mulch thickness of 0 to 9 mm when the soil moisture was higher than 8.4%. Furthermore, the function of aggregate mulches on restraining evaporation was highest between 1130 and 1330 h on sunny days. When the solar radiation and the soil moisture were at a low level, minimal difference was observed in the evaporation rates among the treatments. For the soil temperature, aggregate mulches were more sensitive to the intercepted heat, resulting in higher temperatures on the mulch surface than on the bare soil. Moreover, the effects of the aggregate mulches on soil evaporation and temperature were weakened when the aggregates disintegrated. The findings in this research are helpful for understanding the evaporation process in loess soils with burrowing ants. Maintaining a large number of burrowing ants or a relative constant cover of ant-derived aggregates on the soil surface could restrict soil evaporation.