Sunday, May 23, 1999 - Page updated at 12:00 AM

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Dirt -- Life And Death, War And Romance

ALL THAT IS SWEET and foul in life - all that is sensual and gritty, alive and decayed, simple and complex, ancient and new, rich and poor, warm and cool, is represented by the squeeze of spring dirt in the palm of your hand.

Soil feels alive because it is. Open your fingers and you are holding more microscopic creatures than there are humans on Earth.

Dig beneath the ground and you'll find more total life, or biomass, than exists on top of it: from worms to fungus to bacteria that have been found in drill holes thousands of feet deep. It is estimated that the amount of living matter under each acre of dirt exceeds the bulk of 10 draft horses.

You can smell some of this fecundity. The rich perfume of a freshly turned garden comes from actinomycetes, a higher-level bacteria similar to fungi and mold. What you sniff is the life that truly drives the world. Garden soil the size of a pea can hold a billion bacteria.

We wash because these tiny creatures (a line 25,000 bacteria long would only stretch an inch) can poison us: A spade routinely hauls tetanus microbes to the surface. Yet bugs have also saved millions: The drugs penicillin, streptomycin, tetracyline and neomycin all come from the bacterial molds of the earth.

A square yard of Northwest forest soil contains about 250,000 insects of 250 different species, representing as much diversity as the tropics. They graze on the billions of bacteria and 100 coiled miles - yes, miles - of fungal thread found in every teaspoon of soil, said Andy Moldenke, the forest-soil guru of Oregon State University. As they crawl along plant roots, feasting, these animals defecate broken-down nutrients that become the primary food that root hairs can absorb.

It's a crucial partnership. Eliminate soil critters and plants would starve and die. Sterilize the soil, and we doom ourselves.

"If you were a Martian ecologist who came to Earth, you would pay no attention to people and zebras and elephants and cats and all the things we think are important," Moldenke said. "You would understand that all life nutrients come from organisms in the soil, and would concentrate on them. They are the crucible of biological diversity."

WE NORTHWESTERNERS are made of mud, in the sense that our food comes from soil. Adam is the Hebrew word for "wet clay," and the biblical story of his creation is echoed in modern science. Researchers have theorized that clay's microscopic pattern became the template on which Earth's earliest organisms assembled.

And we return to mud, or dust, in the sense that dirt - what author William Bryant Logan calls "the ecstatic skin of the Earth" - is an endless recycling of all the life that has gone before. When historians sought to exhume the bones of colonist Roger Williams, they found the roots of a nearby apple tree had consumed the calcium in his bones and formed a pattern of living tissue that mimicked his skeleton.

Dirt is rot and regrowth. Charles Darwin estimated that all the good soil on Earth has been eaten and excreted by earthworms at least once. A worm will eat its weight each day, breaking down dead plants into necessary nutrients.

In good compost, a single worm can produce a thousand offspring in a single year. So beneficial are they in breaking down organic debris and aerating soil that Agriculture Department experiments showed a worm-populated plot grows vegetables at five times the rate of a wormless one.

A study of a Danish forest counted 1.5 million worms, and 6 million worm channels, per acre. Northwest farm soils are relatively worm-poor - we've tended to eliminate native ones and European immigrants don't do well here - and so our soils compact more than we would like, reducing their fertility.

OUR LANGUAGE REFLECTS our mixed feelings about the stuff underfoot. Scientists prefer the word "soil," a more refined term taken from the Latin root solium, meaning seat, that includes organic material. The commoner "dirt" comes from the Old Norse drit, or excrement. Dirty looks. Dirty pictures. Dirty deeds.

To be "older than dirt" is to be old indeed. Yet the Earth recycles its crust so vigorously through erosion and volcanism that two-thirds of the land we walk on has been made in just the past 4 percent of the planet's history.

Here in the Puget Sound basin, dirt is far younger than that. We live atop glacial deposits dropped by an ice sheet less than 14,000 years ago. Most of our terrain is dense hardpan - compressed by an ice sheet that was up to a mile thick - with a 2- or 3-foot looser layer of rock, sand and clay dumped by glaciers on top. Our organic soil "skin" is frequently only inches deep.

The Mount Rainier mudflows that buried the future sites of Enumclaw, Orting and Auburn are less than 5,000 years old. They left a sticky smear that drains too poorly to make much more than pasture.

And the rich river soils of the Nisqually, Puyallup, Green, Snohomish, Skagit and Nooksack valleys - a bottomland collection plate for the best the eroding Cascades delivered - date back just a few millennia.

"Some of the best farming soils in the world are in our river valleys," said Craig Cogger, a soil scientist at Washington State University's Puyallup extension-research station. The land is young, rich, wet and "unlike other farming areas, they're not very erodable."

Yet we're losing them in a different way. "Basically, we're just paving them over."

THAT'S WORRISOME, because dirt is strategic. Our vast Midwest reserves of it made the United States a mecca for immigrants and an economic world power.

Egypt endured and Babylon fell because of dirt. The Nile floods replenished Egypt with fresh soil for 5,000 years (until construction of the Aswan Dam), while the desert around the Tigris and Euphrates rivers was so relentlessly irrigated by early civilization that it accumulated salts. An ancient Eden turned into the wasteland of the Gulf War.

We could repeat Babylon's mistakes. Eastern Washington's farm fields have lost some of their organic matter and their microorganisms because of intensive farming, said Ann Kennedy, an Agriculture Department soil scientist in Pullman. Researchers are working hard to reverse the trend.

Eroding dirt is eroding life. Windblown soil is so rich with microbes that it can be traced back to its origin by the molecular fingerprint it carries of microbial remains.

There is sharp debate about how best to maintain these bugs. Recent practice has been to plow in stubble to restore organics, but the extra plowing may do as much harm as good to the microscopic communities. New research suggests soil may actually do better if stubble is burned, allowing reseeding and roots left undisturbed to decay naturally.

Dirt! Pioneers walked two thousand miles to get to Oregon's dirt. Hitler invaded Russia to seize Ukrainian dirt. Romans sowed the dirt of their Carthaginian archenemies with salt. William the Conqueror stumbled after landing in England and seized the ground as an omen of victory. Columbus kissed the ground. Symbolic stuff.

And, as Dr. Frankenstein would say, "It's alive!"

AN OUNCE OF CLAY is a miniature city with more rooms than New York City. What looks solid to us is, on the microscopic level, a myriad of passageways made of tiny clay "bricks," or particles. A dirt cube half an inch on a side can contain 10,000 layers, stacked like the pages of a book and divided 10,000 times more by length and width. A book's pages have room for thousands of words. Unfold all the floors, walls and ceilings of a lump of clay and the resulting surface layer of that ounce, scientists estimate, is 10 acres.

Don't call that backyard garden a plot, Hoss. It's a gol-darned Ponderosa.

Small wonder that a thimbleful of dirt can be home to perhaps 5 billion bacteria, millions of single-celled protozoa and hundreds of thousands of insects. The rich, sticky feel of good soil comes from the slimy bodies of billions of dead bacteria - from smeared cells and bug poop.

Appreciate it. So vital are these organisms to tree growth that University of Washington researcher Jim Marra has recommended that logging be modified to leave shade trees on hot dry plots and clumps of trees on steep, erodible spots. Both reforms, he said, would help preserve the microbes and insects vital to the next generation of forest.

Without a microscope, we are blind to soil's complexity. One square yard of lawn can contain 10 billion root probes from the grass, each far slimmer than a human hair. A single rye plant puts out enough root filaments through the soil to reach across the United States twice.

Astounded at the persistence of weeds? A square yard of turned garden contains 30,000 dormant weed seeds, most of which will never germinate but which will persist for years, waiting for a chance to sprout. (One Arctic seed germinated after an estimated 6,000 years of dormancy.)

Dirt is bustling with soil mites, miniature spiders, sow bugs, centipedes, beetles, maggot flies, worms, springing insects called springtails, ants and fungi. Snails crawl like tanks. Mammals plow, with a gopher once measured to have dug 500 feet of tunnels in three months.

Some of these organisms have formed beneficial partnerships. Douglas-fir trees rely on mycorrhizal fungi to help their roots extract nutrients from the soil, and the tree feeds the fungus in turn. More than 2,000 species of fungi have evolved to take advantage of this cooperative agreement, scientists estimate. University of Washington graduate student Erica Cline has found that just one summer after planting, fir seedlings on one site harbored 40 different species.

And some organisms are at war, as detailed in the David Bodanis book, "The Secret Garden." Ants are shiny from the antibacterial compound they squirt on their shells. Competing plants can send poison-gas attacks at one another through root tunnels. Willows excrete a pest-fighting poison that is the chemical basis of aspirin.

Plants being attacked by insects can release an alcohol scent that attracts a yellow jacket which, in turn, will eat the attacking bug.

When pine beetles burrow into wood, they deposit fungus spores that grow in the bore-hole nurseries, a "farm" that feeds the beetles. In defense, the pine injects the fungus with poison to kill the insects. Surviving beetles respond by converting the poison to a chemical signal to attract a mate. The pine hits back by sending its own signal to attract beetle predators. And so on.

These evolutionary conflicts have been developing for millions of years. Intervention with shovel, hoe, spray, fertilizer and seed is temporary and probably hopeless. Yet left to itself, nature does achieve an equilibrium, which is why a forested hillside can produce a more intricate garden than any of us can dare achieve.

DOWN IN THE DIRT, life isn't very sacred. Spores, seeds, eggs and pollen are produced in fantastic numbers because individual life is so brief and fragile. One puffball on the forest floor can contain 7 trillion fungal spores, each theoretically capable of producing another puffball. If all grew to full size, the volume of puffballs would be 800 times that of Earth.

In fact it is death - the decomposition of life into the chemical molecules that plants need - that keeps the whole thing going. And a good thing, too.

A single female aphid, if unmolested, could produce several million pounds of aphids in a summer. Beneficial insects such as the ladybug are the super-heroes that keep the Earth from turning into a monster movie: One ladybug can eat 5,000 aphids in its lifetime.

It's hard for us to understand life at such a basic level because it's where biology meets chemistry and physics. There is a raucous symphony of chemical signaling going on that we can't sense. A tomato plant, for example, can produce a muscle-freezing protein that can temporarily paralyze an attacking caterpillar, forcing it to fall off. Geraniums pump out poison to kill mites. Trees communicate with one another by sending off warning gases when attacked by insects, triggering the defenses of neighbors.

There is also a profoundly different feel to this miniature world. Ants are so small and light that they can climb straight up and down because gravity exerts little pull on them. Fairy flies are so tiny that air, to them, feels as thick as water.

Dirt can also defy common sense. We might assume our Northwest forests have particularly rich soils, given our particularly big trees. In fact, the needle and leaf litter dropped by trees is consumed by decay about as fast as it is produced, meaning forests usually have thin soil, often only a few inches thick.

Yet a tree needs only trace amounts of dirt to make itself, despite its extensive roots. It is a kind of magic act, a creation of sunlight, water and air that goes thunk. But without the recycling of crucial trace nutrients that goes on in dirt, the tree dies.

The American prairie or Russian steppe, in contrast, can build up soil 60 feet thick because their underground root systems decay more slowly and build up layer by layer. When we break this sod, it erodes quickly: One study in Missouri indicated that a third of its soil has been lost since farming began.

FORTUNATELY, WE HUMANS can improve soil as well. We can hurry recycling along by composting garden waste. The world's domestic animals produce 2 billion tons of manure per year. (A single cow can contribute 15 patties a day.) We can fertilize, seed and water. While the talking-to-plants fad has faded, you do exhale necessary carbon dioxide on any green thing you chat with. Stroking it may release ethylene gas, a signal for plants to produce fungus-fighting poisons.

What we can't do is take dirt for granted. We don't really know how long our farm soils will last. We don't really know how many crops of trees we can grow. We may be clever enough to sustain our soil. Or, like Babylon, we may not.

We do know that nature is on our side. Fourteen thousand years ago, our Northwest had been swept almost clean by that glacial ice sheet almost a mile thick. Left behind was rock, sand and silt as barren as the moonscape of Mount St. Helens. All that we see has come since then, creating a new Eden.

So breathe deep its pungent aroma. Just try not to think about the several thousand mites, spores, pollen bits and bacteria that can be inhaled with every breath.

William Dietrich, author and former Seattle Times reporter, writes Our Northwest for Pacific Northwest magazine.

Copyright © 1999 The Seattle Times Company


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