Written by Emma Reed

Soil. You probably never think about it, but you really should. 

Like the beach connects land to sea, the soil beneath our feet joins the Earth’s bedrock to the air, water and life above.  Now, scientists are exploring how soil changes, and is changed by, the world around it.

“Soil is the magical medium that recycles the natural world we rely on,” says Aaron Bugaj, Research Technician at the Landscape Evolution Observatory (LEO).  “Over the last couple hundred years, as we’ve industrialized our food and added fertilizers to our crops, we’ve degraded our soils. Without healthy soils, you lose your forest, your ability to grow crops and produce food.”

At LEO, scientists have elevated soil from obscurity to center stage.  Manicured basalt rubble sits on three sloped platforms, each the size of a basketball court.  LEO is protected from the elements by the massive glass enclosure of Biosphere 2, which lets scientists fine-tune and monitor LEO’s environment.  The bare, black soil might resemble a post-apocalyptic landscape, but beneath its surface, life is thriving.

Beneath the glass enclosure of Biosphere 2, LEO’s basalt soil slopes bristle with 1800 sensors, which monitor water, carbon, and energy cycling as the environmental conditions change. (Photo Credit: Emma Reed)

Beneath the glass enclosure of Biosphere 2, LEO’s basalt soil slopes bristle with 1800 sensors, which monitor water, carbon, and energy cycling as the environmental conditions change. (Photo Credit: Emma Reed)

In natural ecosystems, an acre of soil can contain enough microbes to equal the weight of two cows, says Aditi Sengupta.  She’s a soil microbial ecologist who uses LEO to answer big questions, such as how soil life will respond to climate change.

“If we didn’t have microbes in our soil, nothing would decompose,” Sengupta explains.  “The plants wouldn’t grow, because microbes release nutrients, which plants take up.  We wouldn’t have food, we wouldn’t have oxygen to breathe…soil microbes play such a crucial role, and people don’t focus on them that much.  You know, ‘Out of sight, out of mind.’  You can’t really see it, so you don’t consciously think about it.”

Fortunately, Sengupta has a simple tool to make the invisible visible: Petri dishes.  She pulls a stack from her lab’s walk-in fridge.  Inside are microbes sampled from intervals along the slopes of a LEO prototype.  They grow in colonies of pinks, whites, blues and yellows, splotches of color that transform invisible soil life into miniature Jackson Pollack paintings. 

These colorful microbes are only the smallest indicator of the life beneath our feet.  With Petri dishes, “we only capture one percent or less of what’s out there,” Sengupta says.  “That’s why high throughput gene sequencing is so valuable.” 

When the full-scale LEO experiment begins in January, Sengupta will use gene sequencing tools to document changes in the diversity of the soil’s microbes.  During this time, researchers will vary LEO’s temperature and rainfall to mimic the effects of changing climate.  “The goal is to study how the movement of water and how geochemical weathering of rocks affect the development of life,” says Sengupta.  “In arid regions, we are expecting to see erratic precipitation in climate change scenarios.  So, how does a place like that respond?  How do the microbes respond?  How does water flow respond?  Does the weathering in those places change?”

This research has important implications, as Science Director Peter Troch explains: “Aditi’s work is critically important to develop fundamental understanding of how landscapes evolve from a dominantly abiotic system into a self-sustaining ecosystem, knowledge that will ultimately allow us to better predict how landscape and ecosystems will respond to climate change.”

Ultimately, the results from the LEO project could improve climate models “that would be better in making predictions about the impact of climate change on our ecosystems,” says Troch.  “We can then design measures of mitigation and/or adaptation if climate change becomes irreversible.”

LEO scientists have already found some surprising results.  When scientists watered the basalt soil, it began to weather, which lowered carbon dioxide levels of air trapped within the soil. LEO’s soil is young and relatively sterile, so its microbes did not produce enough carbon dioxide to compensate, as in natural ecosystems.  Minerals use carbon dioxide as they weather.  In fact, some researchers have proposed spreading basalt onto beaches to pull carbon from the air, helping to reduce the severity of climate change.  These results from LEO show that this solution might not be effective.

From climate to agriculture, soil affects and effects the world we live in.  Soil’s secrets may hold the answers to many unresolved questions on the past and future of our environment.  At places like LEO, scientists won’t let those secrets stay buried.

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