Ed. note: It’s the week of the first in our webinar series The Dirt on Soil! To celebrate, this week’s piece in our curated series of articles on that topic is written by one of our long-standing contributors, Adrian Ayres Fisher. Adrian talks healthy soil, trees, crawdads, and how they all hang together for healthy ecosystems.
Healthy soil is important, but for whom?
In the Garden
The young bur oak would not be kept down. Yet again it revealed itself among the standing dead stalks of a large patch of purple bee balm, a good three feet tall and leafing out. In spring, a bur oak’s leaves look like sharp-edged, glossy cutouts. They are not green, but shade delicately among soft corals, tans and pinks. The green comes a bit later, like a slow-motion wave gently pervading each leathery leaf. The question, as it had been for several years, was what to do with this young newcomer to the garden.
About ten feet away and across the walk from house to garage stands a second bur oak that I’d started from an acorn some twelve years ago. I’ve enjoyed watching it grow its first sets of true leaves, become large enough to attract birds and then mature enough to bear acorns. This winter I limbed it up three feet from the ground, mainly to give the sedges and wild geraniums growing underneath a little more room. As oaks go, this one has only just reached toddler stage, though it’s taller than the garage. It could grow another fifty feet and live, if all goes well and people who come after me don’t murder it, another two hundred years at least.
But back to the youngling. I had, a couple of years in a row, cut it down in the winter, pretending it wouldn’t grow back, since I couldn’t quite bring myself to outright kill it. This was in fact magical thinking, since bur oaks are designed to grow back stronger after burning, cutting or browsing by deer—if you want to grow a strong bur oak, when it’s quite young you might intentionally cut it to the ground once or twice. It will rebound with extra vigor. Clearly this had happened. Yet I felt hesitant about just letting it grow. Two oaks in one 35-foot-wide yard? Though the yard is deep, and they’re placed back towards the alley, yikes! Last summer, again, it grew a couple of feet, hidden by the purple bee balm. This winter, though, I did nothing. Come May, when I went to cut down the old bee balm stalks, there it was, leafed out, with tiny, pink leaves forming at its central apical tip. I surrendered.
However, not only its winsome looks convinced me. During their first few years, oaks grow slowly. That’s because, like the hickories, their sometimes woodland companions, and like the herbaceous plants with which they share habitats, they put a great deal of energy into developing strong root systems before they gain much height or girth. Anyone who has started a native plant garden or restoration from seed knows the several-year-long, sometimes anxious wait before the plants morph into their glorious, blooming maturity. With bur oaks, patience is rewarded, as a puny little thing develops into a presence to be reckoned with, supported by a serious span of roots growing deep and searching widely for nutrients and companionship.
As they grow and mature, bur oaks will first develop a central tap root heading straight down from the erstwhile acorn. That they augment with strong lateral roots extending many feet that help stabilize what will grow into a mighty structure. These roots branch out into finer and finer networks delving 18 inches and more underground, seeking nutrients and developing companionate relationships with other organisms along the way. These include: the mycorrhizae that wrap around and interface with the roots while extending their hyphae even further as they scavenge mineral nutrients to trade with the tree for carbon sugars; and the bacteria, nematodes, arthropods, and other critters that live in the root zone (the rhizosphere). All of these organisms’ relationships and lifestyles help develop and maintain the living soil in which they exist.
Oaks also seek other oaks with whom to form communities. As their roots form their far-flung networks, they are also searching for other, familiar-seeming roots. How they know they’ve found the right ones is a mystery, but they do. Once recognized, the root systems graft together, enabling the trees to share nutrients and send chemical messages to their companions. Sometimes this behavior can lead to disaster, as when a grove of red oaks succumbs to red oak wilt within a single season, or when herbicide is used and spreads to other individuals. Mostly, though, this root grafting is a good survival strategy and, as in other tree genera, allows larger parent trees to help out younger ones.
While I was dithering, I knew the young oak’s roots had kept growing. I imagined them, along with several species of mycorrhizae, extending, touching, somehow recognizing, grafting, and then sharing nutrients and communication. Am I only imagining that the younger tree has been looking perkier and growing better as a result? It seems whatever harm I do to the younger tree will redound to the older one. Consequently, I’ll now have two sizable trees in the backyard, growing closer to one another than is generally considered desirable—by humans anyway. In woodlands and old oak groves some of the trees grow very close together, indeed, some even nearly touching at their bases as their girths have grown large, while others stand further off. This is true of the swamp white oaks in the small forest preserve I steward, as well as in other places, such as a local savanna where groups of red and bur oaks stand close together. I don’t know if there is interspecies root grafting or mycorrhizal connections. Oaks growing like this don’t develop such far-spreading canopies as do the iconic lone oaks on an open lawn or prairie. Yet, as Doug Tallamy and others have noted, closely-grown oaks gain in resiliency what they sacrifice in grandeur. Their grafted, sturdy root systems offer each tree protection against storms and high wind events, which also makes them safer trees in places humans live and work. In fact, Tallamy suggests planting three or so oaks on six-foot centers to form a backyard oak grove. Ten feet isn’t six, but it’s close enough, and because the roots burrow so deeply, I’m not afraid that they’ll buckle the walk between them.
Other than the fact that I love these oaks, both in my garden and in the woods, with a passion that helps drive my work and sits at the heart of my adherence to a practice guided by Aldo Leopold’s land ethic and the ancient law of reciprocity, there is a point to this story. The two oaks have formed a relationship enabled by the soil in which they grow. The soil is superb, formed over millennia by the prairie on which my house was built almost 120 years ago. Remarkably, gardeners have always lived here, and we have always cared for the soil. I am the most radical, I suppose, since I have eschewed “conventional” gardening for helping communities of native plants develop around the house, until it looks quite wild. And therein lies the point.
The oaks are growing within and contributing to a community of multiple savanna and woodland plants native to Illinois and appropriate to the natural ecosystems in Illinois in which bur oaks grow. The soil in which they grow is not a fixed entity—it’s always breaking down and reconstituting through time. The trees are healthier because of the herbaceous plants and shrubs among which they grow—and vice versa due to the oaks’ presence. All together, these plants and their partners of other species—the fungi, arthropods, bacteria, et alia, are creating the soil in which they are growing. This project is helped along by above-ground organisms such as mammals, birds, and insects, in the never-ending creation process of the ecosystem, with its myriad relationships, processes, stocks, and flows. In my yard, soil is not depleting, either in quantity or quality.
Hierarchically Nested Processes
Over the past few years, I’ve come to think of living soil, the larger ecosystem community of which it is a part—and all of life—as a stabilized system of processes rather than a grouping of objects or things. For example, we humans are not objects, but rather systems composed of “hierarchically nested processes occurring across a number of time scales” (as described by Daniel J. Nicholson and John Dupre), ranging from the fractions of seconds required by bodily functions at a cellular level to the decades-long average lifespan. Among other things, this helps account for the fact that what we think of as our bodies’ composition actually includes multiple other species such as the bacteria in our guts that enable digestion. This mutualistic relationship blurs the boundaries between us and the outside world, since without them, we’d neither be able to access nor utilize nourishment. Yet the bacteria depend upon us as well. It is through change embodied in such intertwined processes that our bodies are stable and able to function.
By this paradigm, soil is the name we give a particular processual community, which is a nested part of the larger ecosystem community, and whose boundaries are blurred. It’s very difficult to tell where the soil and all the living things that live in and around it, begin and end. There is duff in the woodland, no longer leaves and other organic detritus, but not yet exactly what we think of as soil. In a prairie, there are the intermingled deep and shallow roots, roughly a third of which die each year—fertility-building organic material. But does the fact that they are no longer functioning as roots—starting to break down as part of the decay process in which water, weather, and so many living organisms play a part—mean they are soil? Yes and no. Or not yet. Everything is mutable, is becoming, is in a process of transformation.
As part of this system, we have all heard that trees sequester a great deal of carbon—basically they are carbon—and so we should plant more of them. True, so far as it goes; but in reality, trees by themselves won’t do it, in the same way a lawn won’t sequester carbon, but a prairie will. Healthy biomes comprised of all the interacting living organisms therein comprise the best carbon sinks, because it’s the cycles, the hierarchically-nested processes, that enable carbon storage deep in the ground. The community is everything.
In any ecosystem, which plants form a given community depends partly on the parent rock from which the soil is made. (Light, moisture and climate also come into play, of course.) Soil organisms and organic material help determine the fertility. We talk of soil as having “components”—so much sand, silt, or clay material. These components, derived from various kinds of parent rock materials, are themselves the result of geological and climatic earth cycles or processes. The parent rock contributes structure and determines the available minerals and the pH level—whether the soil is acid enough for blueberries, desirably neutral, or base enough to nourish the rare plants that grow in dolomite limestone prairies. But soil isn’t really soil until the organic material derived from the lifecycles of living organisms, and the activities of these organisms themselves are added—it’s just rocks ground up over eons. When the continuing, interlocking, ongoing system of processes involving complex, interlocking cycles of living and dying stops, you no longer have soil.
If you’ve read this far, you might begin to see some of the foundational and conceptual problems involved in pursuing the modes of thought and logistical procedures that constitute much agricultural and gardening practice. These practices, such as monocropping with annuals, mostly attempt to superimpose simplified, linear human systems on the hierarchical, nested processes of natural ecosystems.
What It Means to Deplete the Soil
It is a truism that conventional farming and gardening deplete the soil. But “deplete” really means that they kill the soil—shut down the nested processes—and, by extension, nearly everything else in the ecosystem except what anthropocentric crops or ornamental plants are in the ground. Insects decline. Birds decline. Wild native plant species decline. Important soil fungi and subterranean species decline. Nitrous oxides and carbon dioxide flow out of the ground into the atmosphere, adding to greenhouse gas pollution.
When we talk about depleting soil, in part it means that the plants we are growing are accessing nutrients. When we harvest and carry them away to be eaten or used, the soil nutrients that normally would get circulated back into the soil also leave. If nothing is done to restore the soil, and then the wind sweeps through bare fields, it literally shrinks—its level falls—which we call losing topsoil. This is why farmers around the world developed techniques—such as fallowing, rotation, milpas, and swidden systems—to return fertility, so the land would continue to bear. In my region, for example, the Potawatomi would periodically move their villages and fields in what ultimately was a large, circular pattern, in order to allow previously cultivated land to rewild and thus regain fertility.
Only our modern industrial civilization has been arrogant enough to assume we can supply the soil with mostly fossil fuel-derived inputs to grow what we want, as long as we want, often in places that are, in terms of available water and other conditions, wildly unsuitable. With this approach, a field or garden of artificially maintained, individual plants replaces an intertwined, multi-species community. This could be seen as an extension of the way the forces of hyper-individualistic, capitalist society have preyed upon and attempted to replace complex, land-adjacent human societies. Naturally our society would farm this way! Only recently, have conditions changed somewhat. For example, only under the duress of extended drought in the west, has loyalty to growing a well-watered green lawn and perhaps certain water-hungry crops, perforce begun to wane.
I don’t have an answer. I am not a farmer. A key tenet of the kind of native plant gardening and small-plot vegetable gardening that I and many, many others do is to focus on and grow plants that are suitable to place and soil. I used to grow more vegetables than I do now in a sort of semi-permaculture way, but mostly stopped when I realized that it’s much easier for me to procure healthy food than for all the non-human species to do so. My small, wild garden has become an oasis where native bees nest and threatened birds stop during their long migrations. I depend on farmers to provide food so I can provide habitat; but on the other hand, I am, in a way, helping farmers pay down their debt to the land. I can’t tell farmers what to do. I know many have their own struggles to make an honest living. Yet my heart grieves for the destruction of living prairie soil, and all the species that might not make it. I fervently hope that regenerative farming and ranching will make a difference before it’s too late.
Healthy Soil for Whom?
One day this spring I happened to be walking off-trail in the preserve I steward, a patch of high-quality floodplain forest on the banks of the Des Plaines River, where sometimes it’s hard to tell where the land ends and the river begins. It had been raining for several days. The river was running high and fast, and inland the ground was almost beyond mucky. I was walking carefully, so as not to crush anything, along a sequence of vernal pools that together are part of a long, narrow seep that extends south of a pond, part of a low, lengthy depression that runs along the path of the river to the west. To the east, the land rises towards what a hundred years ago would have been a mix of savanna and prairie, but is now roads and buildings.
I walked in just to see what was there, in particular just how far a skunk cabbage patch extends along this roughly north-south axis—much further than I’d known, it turned out. I got kind of excited. Skunk cabbage is a good indicator of seep habitat, and large patches of wetland aren’t that common around here. A rare, red-shouldered hawk flew from tree to tree ahead of me giving its shrill call. Robins, cedar waxwings, and others commented, while toads hopped out of the way of my lumbering feet. Huge skunk cabbage leaves flared almost lime green in the semi-gloom. Purple-stemmed, great Angelica stood nearly six feet tall, their large leaves just starting to unfurl, like hands reaching out to sun and air. There were a number of sedges, jewelweed, marsh buttercup, and some ubiquitous non-natives such as creeping Charlie. Plants grow here that indicate that the land has never been cropped, or even heavily grazed. A couple of downed trees carried large loads of shelf fungi, lichens, and mosses. Carbon was being sequestered all around. The soil was definitely not depleting in any way.
I was moving very slowly, eyes down, looking at leaves, looking at some of the blackest soil you can imagine, technically a fine-textured silt loam. In this flat composition of green and black, something red flashed, scuttling. What? The creature practically jumped into a round cavity that had somehow held its shape in the mud. I stared at it. A pair of beady black eyes on stalks peered back at me, large claws wrapped around the front of its segmented body, and antennae quivering atop its head. Top to tail, I estimated about 5 inches. A miniature lobster somehow transported to the Midwest? Nope, a crayfish, a crawdad, just like the old song, something I’d never seen living free before. They might be common in wilder places, and definitely down south, but here? Oh joy that this place is so muddy, so often flooded, that it was never deemed worth “doing anything with.”
Yet, I can imagine a farmer thinking what he could do with soil so black, so obviously full of organic material, so obviously fertile. Thanks to the river, not even a system of French drains such as pervades much of the rest of my part of Illinois, formerly a soggy place characterized by flatwoods, marshes, swamps, vernal pools, bottomlands, floodplains, riverine environments, wet prairies, sloughs, bogs, fens and the like, would have made the land worth farming. No one was ever able to “reclaim” it, cutting down the centuries-old swamp white oaks and hackberries and commencing to farm it until it lost its livingness. Lucky, that. This little crawdad and its progeny—like its ancestors going back, maybe millennia—are able to dig their flooded burrows and live their lives among the other plant and animal species that depend on this variety of good, productive soil suited to their needs, and which they help maintain.
So, when we talk about good, healthy soil, when we talk about avoiding the loss of topsoil, what are we talking about? Too often we are talking about soil subject to the discipline of the farmer. It is necessarily so. We must eat. But the land sacrifices so that we may live; the land ethic asks that we live in ways that show we are responsible citizens of the land community; and the law of reciprocity asks what we are giving back in return for that gift of life. By standing aside from the ecological community, our profit-driven society has accrued debts we will be hard put to pay back. What kind of restitution can we make to the other species, to the processual structures and systems upon which we depend?
Hard questions. Yet in that moment, at that spot—surrounded by multiple species of animals, by tall old oaks, hackberries, and basswoods, by mosses and fungi, by herbaceous plants erect, sprawling, and creeping, leaves expanded full of water, photosynthesizing like crazy, roots helping structure the soil, just water and mud and plants everywhere, and all the creatures going about their lives—enthralled by the sheer beauty I stood stock still, just breathing and looking, breathing a quick word of thanks to be alive and there to see it all that day.
- How I came to plant a bur oak in my backyard: “A Question of Trees”
- More about farms and carbon sequestration: A View from the Air: Carbon Sequestration, Midwestern Farms and Biodiversity
- “The Angel’s Glow: How the Soil Healed Wounded Soldiers, video by Sustainable Human
- “Building a Loving, Healthy Home for a Tree,” by Gerould Wilhelm, Conservation Research Institute
- “The Crawdad Song,” Woody Guthrie performance on YouTube
- “Entangled Life: How Fungi Make Our Worlds, Change Our Minds and Make Our Futures,” by Merlin Sheldrake (Random House Trade: 2021)
- A Manifesto for a Processual Philosophy of Biology, by John Dupre and Daniel J. Nicholson. In “Everything Flows: Towards a Processual Philosophy of Biology,” ed. Daniel Nicholson and John Dupre (Oxford University Press: 2018)
- “The Nature of Oaks: The Rich Ecology of Our Most Essential Trees,” by Doug Tallamy (Timber Press: 2021)
- Soil Health: The Unseen Foundation of Biodiversity, by Irene M. Unger in “Missouri Natural Areas Newsletter,” Vol. 17, No. 1, 2017
- “Wild about Illinois Crayfish!,” Illinois Department of Natural Resources