nature.net
December 2006–January 2007
The Good Earth
By Robert Anderson
The soil underfoot rarely gets its due. As a geologist, I viewed soil—when I considered it at all—as an impediment, an annoying, transient layer hiding the interesting bedrock beneath it. Nevertheless, when I worked at the American Museum of Natural History, I was repeatedly drawn to Living in the Leaf Litter, a diorama of a forest floor that reveals the hidden world of soil in oversize detail. Under a blanket of giant, decaying oak leaves and an acorn the size of a watermelon, a cutaway displays a burrowing earthworm as big as a python, as well as an unfamiliar collection of arthropods and fungi—all busily building soil for the next generation of trees.
The conservationist Les Molloy described the wonder I felt, in his book The Living Mantle: Soils in the New Zealand Landscape:
For only rarely have we stood back and celebrated our soils as something beautiful, and perhaps even mysterious. For what other natural body, worldwide in its distribution, has so many interesting secrets to reveal to the patient observer?
Because of soil’s economic importance, it’s hardly surprising that the U.S. Department of Agriculture has a page of Soil Quotations devoted to those who have written in praise of dirt. USDA also has a primer on soil biology; the first chapter outlines the vital importance of the subterranean food web.
The Bureau of Land Management has a good site on the biological communities living in western “biological soil crusts.” Click on the “Just for Kids” button on the left of the screen for a kid-friendly version. “Soil,” we are told, delightfully, “is the top layer of the Earth’s surface, like frosting on a birthday cake!” NASA, not to be left out, has a Soil Science Basics page that gives students an appreciation for the time it takes nature to create an inch of decent soil (about 500 years), and for the fraction of our planet’s entire surface that is arable land (about 10 percent). Students who want to explore the underground microcosm at its smallest scale should visit the Microbe Zoo, a creation of the Center for Microbial Ecology at Michigan State University. Click on “DirtLand” and then “Root Cellar” to learn about the rhizosphere.
The Field Museum in Chicago has a wonderful exhibit, Underground Adventure, devoted to life in the soil. On the Web you can tour the exhibit virtually, which gives a good sense of what visitors experience when they walk through the subterranean world in the museum, enlarged to make them feel less than an inch tall. The Smithsonian Institution in Washington, D.C., is working on a major soil exhibit, scheduled to open in 2008. Go to the Smithsonian Soils Exhibit page and click on the movie in the upper right, or “Learn about the Exhibit” to see what the museum is planning.
My favorite Web site on the subterranean world, however, is Thomas E. Loynachan’s Soil Biology Movies. A professor of agronomy and microbiology, Loynachan has sixteen videos on his site, with commentaries that show soil creatures in action. Perhaps the most fascinating of the lot are the nematode-trapping fungi, the Venus flytraps of the mushroom world. Another intriguing site is the Rhizosphere Image Gallery, where soil scientists photograph the underground with a special “root camera” to observe what’s going on below the surface. It gives you a sense of why life in the soil remains mysterious.
Thomas Jefferson penned more than one self-evident truth: “Civilization itself rests upon the soil.”
Robert Anderson is a freelance science writer living in Los Angeles.
Copyright © Natural History Magazine, Inc., 2006