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The top 30 cm of Puerto Rico’s soil is highly bioturbated by earthworms.Credit: Adrian Wackett
Earthworms are hard-working invertebrates that decorate the upper layers of the soil and have long been considered useful in home gardens. Earthworms are prolific eaters, grinding up the organic matter and sediment particles that make up the soil. Although these are completely different animals, like many domestic fowl, nematodes also have gizzards.
“Earthworms ingest larger soil particles and use the strongest and largest particles by holding them in their gizzards,” says Adrian Wackett, a soil science doctoral student at Stanford University. do. These gizzards are great for breaking down the soil and releasing nutrients.
While earthworms may be beneficial to your garden or compost pile, they are invasive and can damage natural ecosystems. The physical weathering of soil (or the breaking down of rocks and sediments into smaller pieces of the same material) by earthworms affects soil processes, such as how much organic matter and nutrients the soil can hold. Also, by breaking down sediment, worms create new soil textures that can affect how water infiltrates the soil and chemical processes.
Weathering is also a major factor in the carbon dioxide cycle. “Geologists often think that weathering rate is one of the major factors controlling the Earth’s ‘thermostat,'” says Wackett. Chemical activities such as sequestering carbon and creating new minerals are aided by mineral-crushing insects. But earthworms also break down organic matter, releasing carbon dioxide into the atmosphere.
Wackett wondered how much mineral weathering earthworms could produce.in new research Presented Wednesday at the Geological Society of America. GSA Connect 2023 At the conference, Wackett and his colleagues will demonstrate that the invasive spread of earthworms, or “global insurrection,” causes significant amounts of silicate degradation.
To better understand how earthworms break down sediment, the researchers studied soil in Puerto Rico’s El Yunque National Forest. They found large changes in sediment size within the soil column, with median particle size decreasing in areas where the earthworms had burrowed. In fact, quartz grains in zones biodisturbed by nematodes were nearly 50% smaller than grains without nematode activity.
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Worm castings remain on the surface.Credit: Adrian Wackett
Although other short-term laboratory experiments have been conducted on insect weathering, this is the first study of silica degradation in in situ soil by insects. The research team found that about 2% of all weathering in El Yunque soil is caused by insects. Wackett adds that this is a conservative estimate of insect weathering, noting that insects may be an even more powerful weathering mechanism than these initial estimates.
Earthworms can spread to new areas, accelerating the rate of weathering. Wackett points out that earthworms are now invading forests in northern latitudes that were previously devoid of them.
The researchers assessed changes in particle size across a range of soil profiles across an earthworm invasion gradient in Alaska, Minnesota, Finland, and Sweden, where the timing of earthworm arrival, and therefore earthworm weathering, is more severely constrained. They found that the median particle size varied considerably in these locations that were historically free of insects.
Wackett concluded that each worm “causes small changes, but when you scale it up, it actually creates quite large changes.” [weathering contributions]. ”
For more information:
presentation. gsa.confex.com/gsa/2023AM/meet … app.cgi/Paper/393829