With snow piled inches deep, the trees ragged and leafless, and scurrying animals forlornly looking for morsels, it is unsurprising that our thoughts turn to spring and its promise of rebirth. Apply a spade or even the heel of your boot to the dirt and confirm that of all the dead wintry things in the world, the soil seems to be the deadest of them all.
In fact, many share the common misconception that dirt is always dead (and not just in winter!). People often think that while soil may contain life to be sure, the soil itself, that matrix that supports roots and provides nutrients for plants, is an inert or dead substance.
On the contrary, however, living things are essential to the proper working of the soil and in the absence of living things soil would not be soil at all.
Living things are such an important part of the soil that in our part of the world, the so-called temperate ecological zone, the greatest species diversity occurs in the upper centimeters of the soil. In fact, because they are so rich in species soil ecologist PS Giller has named temperate soils the “poor man’s tropical rain forest.”
What is soil and why should we be concerned about it?
The classical definition of soil, according to the Soil Science Society of America is “the unconsolidated mineral or organic material on the immediate surface of the Earth that serves as a natural medium for the growth of land plants.” Ouch!
Though technically correct, of course, it hardly promotes a sufficient appreciation of the profusion of life that abounds in the “dirt,” or of the critical functions that living things perform to sustain plant growth and diversity. There is an astonishing diversity of life in the soil, everything from bacteria to mammals and every major living group in between.
These include creatures like termites, beetles, and earthworms, and even some fairly exotic looking creature like pseudoscorpions and primitive wingless insects called springtails. These underground microbes and animals are typically neglected in conservation work even though their protection is likely to make it easier to restore a degraded ecosystem.
Soils and the creatures that live in them are very sensitive to human mismanagement. We need to understand the living and non-living components of the dirt in order to be a responsible soil steward.
Sometimes regarded as the greatest but least recognized scientist of the 20th Century, Swiss born Hans Jenny spent his career in the U.S. He captured the mutual dependence of living, chemical, and physical factors in the development of the soil in an important equation (one that should perhaps be as well know as Einstein’s more famous one).
Identifying the soil forming factors, the equation is written as follows: s = f(cl, o, r, p, t, …)
This can be read as: soil formation is influenced by climate, organisms, relief (the shape of the landscape or topography), parent material (the rock under the soil), and time.
Applied to the dirt in your yard or your favorite forest preserve, it indicates that our Illinois soils are formed as a consequence of moderate climate, gentle topography, with parent material drawn during the ice ages from a variety of sources.
The soils of Illinois are also young (less than 10,000 years old—youthful for a soil). Finally, these Midwestern soils that have been essential for agricultural production are healthy and productive because of all of these above facts and as a consequence of the richness of life found in these soils.
In fact, there can be up to 7,000 different species of organisms in just one teaspoon of soil (NRCS). These bacteria, fungi, insect grubs, earthworms, and other small organisms are hard at work, even in the winter decomposing roots, leaves, branches, and other material under our feet making them essential to the dirt we live on.
Living things are integral to the dirt. Without it, the soil would be simple rock material scattered over the landscape. This material is called regolith by soil scientists a term also used by Apollo scientists for the material found on the dead surface of the moon!
As we look out at the frozen surface in our garden it may be invigorating to learn that beneath the surface, underneath the insulating layer of snow, life is very active in the dirt; decomposing last year’s organic material, preparing the way for the abundance of springtime.
What You Can Do
- Dig in your garden and examine what you find. As we approach spring look for beetles, springtails, sow bugs, millipedes, all performing essential soil functions.
- Visit the Field Museum’s Underground Adventure.
- Take a soil ecology course.
- Consider the needs of the soil in restoration projects.
Written by Liam Heneghan and Lauren Umek