Research undertaken by scientists in China reveals that ants are hardworking and beneficial insects. In the activities of their daily lives, ants help increase air, water flow and organic matter in soil. The work done by ants even forms a type of mulch that helps hold water in the soil.
Ants are busy insects. They dwell in the soil, and build their homes by burrowing tiny holes, channels, and chambers. Soil scientists refer to these as macropores. Where do ants place the soil they are digging out? On the soil surface. The tiny clumps we see as an anthill are what researchers call aggregate mulches.
In addition to creating the aggregate mulches, ants help the soil environment by “Bringing down food sources from outside,” says soil scientist Tongchuan Li. “Types of food include the bodies of insects, leaves, sugar water, and the ‘honeydew’ of aphids. The big diameter of the nest channels (0.15-0.25 in.) and the chambers also can improve the transport of air with frequent ant activities.”
Li and researchers at Northwest A&F University, Yangling, China, found that ant-made aggregate mulches could help retain water in agricultural fields. In other words, these aggregates can act like any other mulch, preserving moisture in the soil, under certain conditions. “Minimal attention has been paid to the effects of ant activities on soil [water] evaporation thus far,” says Li. “Ants represent half of the global insect biomass.” And these mulches could be playing an important role in soil moisture and soil health.
How do ants make these aggregate mulches? “With burrowing their nest, ants make and move the aggregates on the soil surface around their nest,” says Li. “As I observed, Camponotus japonicus just physically bite off and move the soil fragments with their jaws.” Larger ants tend to make larger aggregates than smaller ants – and Camponotus japonicus runs on the large side. The aggregates these ants make averaged 0.25 in.—or 12-22% of the ants’ size. That’s a lot of heavy lifting!
One downside to ant-made aggregate mulches is that they disintegrate with rainfall. However, ants tend to enlarge their nests by making new chambers after a rainfall, producing more aggregate mulches after rains. So, in theory, aggregates are a “renewable” mulch source.
Soil Science Society of America Journal
April 3, 2017 NewTerrain