HANS JENNY, who died in 1992 at more than ninety years of age, was one of the great scientists of this era. Were he not a soil man, Jenny’s achievement might have ranked him with the pioneer ecologist Henry Cowles or with the physicist Clerk Maxwell, but his work has been comparatively buried in the obscurity of his profession. The head of the University of Chicago’s venerable department of ecology, asked to comment on Jenny’s contribution, remarked, “Never heard of him.” And not long ago, at a University of California cocktail party, Jenny told a new acquaintance he was a soil scientist only to be asked about garden tomato plants. This is like asking Toscanini to tune your guitar.
Such incidents are doubly unjust. Jenny’s formula for soil genesis was one of the pioneering works of ecosystems ecology. It is an archetype of whole-systems thinking. It was Hans Jenny who gave the picture a new dimension, with his 1941 formulation of soil process that distinctly linked “deep time” and our time. For Cowles, twenty thousand years was old. Jenny looked as deep into time as the age of the oldest soil he could find: more than half a million years. By including the factors time and parent material in his equation, along with climate, slope, and organisms, he was able to link biology, geology, and duration in a single mathematical relationship. The equation, called CLORPT, describes a set of feedback loops that maintain a living system.
Ecologists sometimes receive unusual monuments. Hans Jenny kept a piece of what may well become his own monument in the lower-right-hand drawer of his desk, which is often where a man keeps what he most values and/or fears. The ninety-two-year-old Jenny pulled open that sacred drawer in his University of California office in Berkeley. “I want to show you something,” he said in his clipped Swiss accent.
He handed me a white lump the size of a softball, but chalky, as though he had been saving blackboard dust for half a century. “Hold it,” he said. “See how heavy it is.” It sank in my hand like a shotput. “Now that has hardly any organic matter in it, hardly any nutrients,” he observed slowly, choosing his words. “But it is certainly a soil.”
It was also my introduction to the pygmy forest, and Jenny’s understanding of ecosystem evolution.
The heavy chalky lump I hefted was, he told me, ancient, Methuselan. With a pH just this side of lemon juice and a subsoil as hard as a frying pan, the soil it came from grew nothing but a few stunted pines and heath plants—acid lovers like manzanita—many of which sickened and died, still standing.
What calamity brought this about, I asked him.
Time, nothing but time. More than half a million years of sitting out in the rain.
Jenny sat regarding the bagged lump with the eyes of a proud father. It represented, I believe, his excursion to the edge of human time, his adventure in truth. For more than two decades since his retirement from active teaching, he had pursued research on this soil, trying to establish how it had come to be.
What most startled me was that the soil was not from a parched desert but from the area widely regarded as unmatched for scenic beauty on the whole California coast. This white dust was from Mendocino.
Several months later, Jenny and I were bound north from Berkeley in his station wagon to see this soil in its place. In the back of the car rattled cans of tunafish and fruit and a jar of coffee, together with a tackle box full of little augers, a hammer, chicken wire, white envelopes, and labels. Somewhere in the wine country of Sonoma, we scooted off onto a side road, and he told me to stop. “What do you see?” he asked.
I saw a hillside with some live oaks, some vines, and some pine trees.
“Well, why,” he continued imperiously, “does the oak grow over here and then the pine grow there?”
Before I could answer, he was out of the car and swinging off along the roadside. He stooped to pick up some small stones and returned to me. In one palm he held a blondish sandstone the color of dried grass; in the other, a handful of small, sharp-edged, friable chunks of a deep-green rock called serpentine.
Here in my own native ground, he had shown me a key to the landscape that I had never noticed. Other factors being equal, a soil derived from sandstone will support oaks and vines; a soil that comes from serpentine is covered with scraggly digger pine.
As we drove west over the coastal hill toward the sun that hovered above a bed of fog, Jenny explained to me that the pygmy forest soil that we were going to see had deeply affected his idea of ecosystem evolution and caused him to question the unspoken idea of much environmental thinking: that, properly treated, nature balances herself in a way that is beneficial to man.
That evening, in the musty-smelling clapboard farmhouse that has been his base for decades, he described the staircase of five marine terraces that step up the hill from the town of Mendocino to an altitude of more than six hundred feet above sea level. The top three terraces contain areas of pygmy forest with its dust-and-iron soil. The underlying rock on which the whole landscape is based is a graywacke sandstone, laid down fast in a deep sea trench about 150 million years ago. It is what geologists call a “poorly sorted” stuff, which means it contains the whole range of mineral elements that, once weathered and made soluble in soil, contribute to plant growth.
Jenny’s picture of soil evolution reaches to a time in the middle Pleistocene, between a half million and a million years ago, when the sea level rose, responding to melting glaciers farther north. As the water rose, waves cut a shelf in the graywacke. Then the glaciers returned, and the sea level fell, the receding water leaving a layer of stones, gravel, and sand on the now-exposed shelf. The glaciers retreated again, and sea level rose, but at the same time tectonic forces of compression along the San Andreas Fault, at the junction of the North American and Pacific plates, lifted this first shelf above the reach of the waves. So the sea began to cut a new shelf, at a lower level than the first. Over the course of the Pleistocene and into the Holocene, this to-ing and fro-ing continues, until like a gigantic escalator the landscape had unfolded at least five shelves, each made of roughly the same parent materials and each slightly higher and farther inland than the next. The oldest is perhaps three quarters of a million years old; the youngest is still waiting to be born.
Overlaid on this stately sequence of emerging shelves is a corresponding set of fore-edge dunes. Each was the result of sand blowing up from the beach and becoming piled on the front edge of the most recently elevated terrace. Thus, each shelf has two ages, one belonging to its own materials and the other belonging to the dune that was later blown up onto it.
This, Jenny asserted, was the history of the landscape that made it possible to study the effect of time on the pygmy forest soil. Though fascinated, I found it difficult to imagine why this sequence of events should result in a soil barely able to support life, as Jenny contended it had. The claim became doubly hard to swallow the next morning, when he drove me to the Mendocino headlands.
Down below us on the beach, we could see sloshing beneath the incoming waves the pebbles, gravel, and chunks of tough graywacke that would be the raw material for a future soil on a still unformed terrace. We were standing at the top of the headland, right at the edge. It looked barren enough on the steep slope of the headland, where lupine, ice-plant, and pinks were holding on in the crevices. But when Jenny turned around, he plunged his hands into an exposed soil profile that was as black and as rich-looking as the Iowa prairies. The soil of the lowest terrace, on which we were standing, is a grassland soil of the sort called “mollisol,” related to the soils of the Midwestern prairies as well as to the famous Russian chernozem. The mutual action of organic acids and the chemical and mechanical weathering of potassium- and calcium-rich graywacke sands had turned the sand to clays, and along the edges of the clay particles clung the blackish organic complexes of humus substances. The soil supported a magnificent meadow flora of nodding onion, wild iris, lupine, buttercup, bunch grasses, strawberry, yarrow, and many more species. How was I to believe that this soil was a younger brother to one not three miles distant that supported more lichens than plants?
We drove up to the next terrace. Not only was there no more prairie, we could not even see the prairie because we were deep in a mature forest dominated by majestic redwoods and Douglas fir, with thick stands of rhododendrons, salals, and other ericaceous (of the heather family) plants. The dense growth made for tough walking, but the acid odor of the conifers, together with the rhododendron flowers and the waxy berries of the salal, were more than adequate compensation for the trouble.
Fifty thousand years ago, if Jenny was right, the place where we were standing had itself been a prairie by the edge of the sea. Propelled by tectonic forces, it was now a little higher and much older than its prairie brother below. The soil here was more weathered, and the soil horizons had become thicker and more distinct. At the bottom of this soil could still be seen the same sands and gravels of the original beach material, but now they were so worn that you could crumble them in your hands.
At the next step in the staircase, Jenny showed me a forest dominated by a towering bishop pine. At first glance, the older soil here seemed to support a plant community as robust as that on the shelf below. But there was less diversity of species, and the forest was less dense. The trees were sending their roots deep, in search of the nutrients that were being leached all the way to the water table, in which they might finally be lost. In this soil, the top gray horizon had thickened, as weathering leached more and more minerals from the surface soil, leaving only the grayish, resistant quartz and kaolinite. The iron drops of the lower horizon had grown more numerous, and some of them were cemented into clusters.
From the aboveground life on the three shelves, I would never have guessed that these landscapes were closely related. Yet in the soil horizons, I could clearly grasp their common origin and their evolution. We drove up over the hump onto the next terrace and took a dirt road onto property that belongs to the University of California. Jenny and his wife struggled for years to get anyone interested in preserving this landscape, and eventually won a state park for one strip of the staircase we had ascended as well as this U.C. study plot in the pygmy forest. “People don’t regard soils as beautiful,” he lamented, “so it’s hard to argue why they should be preserved.” He is only half kidding, maybe even serious, when he suggests turning the selenium-tainted wetlands of Central California into Selenium State Park. The tainting, after all, is the result of the natural leaching of a trace element when irrigation water is poured over the soils.
Leaving the car beside a rut, we walked through a scrubby path of conifers into another world. The tallest trees were scarcely taller than a man, and many rose no higher than our waists, though they were decades or even centuries old. Their trunks were as slender as a mummy’s wrists. Here grew dwarfed, twisted versions of the plants and cypresses on lower steps of the staircase. A few were endemic species, found nowhere else in the world. Almost a quarter of the area was bare ground or covered with yellow-green lichens. Thirty percent of the trees were dead or dying. When they perished, they remained standing, rotting in place.
From above, who could ever say what had caused this apparent catastrophe? Standing with Jenny in an eight-foot-deep soil trench, I could see the answer. The very bottom of this soil, where it met the unaltered graywacke sliced flat by the rising waves of a million years ago, was the same beach sand as on the other terraces, but the horizons above were the sclerotic developments of the processes that were still in full swing on the levels closer to the beach. Beneath a slender, gray-brown top layer was a bone-white horizon at least one foot thick. There were no free nutrients left in this layer, only the most resistant, insoluble quartzes. It was from this layer that Jenny’s lump of dust had come. The metallic elements leached by millennia of rain from that graying surface now formed not teardrops or even clusters of red-brown knots, but a solid, unbreakable hardpan horizon, in places more than three feet thick. To get a piece of it, you had to hit hard with a hammer more than once.
Little could live atop this white-and-red soil. Jenny and his students were still doing experiments to grow other plants here—poppies, grasses, anything. On unaltered soil, nothing at all would emerge. If the soil had been amended with a nitrogen fertilizer, the plants would sprout, use up the fertilizer, and keel over dead.
There was not, in fact, a lack of nitrogen. Because the hardpan prevented drainage, during the winter rains the whole forest was awash in a coffee-brown liquid of water mixed with humus substances rich in nitrogen. But the nutrients derived from the mineral world, particularly phosphorus, were virtually lacking, having leached away, or having been locked up in compounds that were very hard to break and therefore useless to plants. Furthermore, because the soil surface was cut off from the depth, the acidity of the soil had built to such a level that few soil microbes could survive, so that plants growing here would have little access to the nutrients usually produced or converted into usable form by such organisms.
As Jenny and I stood on the slope leading into the soil trench, the old man was filled with the delight of his knowledge. “You see,” he said stooping, “the soil down at the bottom of the trench, beneath the hardpan, has more nutrients than the topsoil. If we find a living seedling, it will likely be down there.” Down we went, though it occurred to me there was some chance that his body, so old he could scarcely keep his head erect on his neck, would never leave the trench.
We scrabbled about in the red subsoil until we found a tiny seedling, perhaps two centimeters tall, of the endemic bolander pine.
“Now that is a seedling two years old,” he said exultantly. Anywhere else, it should have been inches, not centimeters, high,
When he stood up again in the trench, his eyes, like mine, rose just a few inches above the soil surface. “It’s beautiful, isn’t it,” he breathed, looking out over the miniature, contorted landscape.
I wondered what he could mean by that. He had shown me that an apparently random assemblage of landscape features had a deep underlying order whereby prairie turned to forest, turned to pygmy forest. Soils, under the influence of time, were largely responsible for the changes.
“Your ideas are beautiful,” I told him, “but this landscape is frightening.”
Jenny had stood me on the boundary between deep time and our time. I could not avoid the feeling that we are just one experiment in a more ancient world. “What does nature have in mind in making soils?” he had once asked. In light of the pygmy forest, he could not answer with the communitarian optimism of a sanguine environmentalist. Over the long haul, nature was not in the business of making pleasant places for people to live. Quite the contrary, it seemed interested in pushing the limits of the relationship between the organic and inorganic realms, producing new experiments like the scraggly bolander pine.
Yet to Jenny this is a cause for wonder, not despair. His study provokes the most difficult beauty, the one that we would often as soon leave buried in that lower-right-hand drawer. It is a beauty that admits the underground, the underworld, the soil, the dirt, heat, decay, cold, smells, soluble metals. It may be a hideous, misshapen, twisted, threatening thing on the surface, but musically beautiful in the laws by which it lives. According to the poet Rilke, Orpheus never sang so sweetly as when he went to the land of the dead.
Certainly, the scientist could accept such a characterization of what he meant by “beautiful.” When I said I thought the landscape frightening, Jenny did not even turn his head. He kept looking out across the dwarf forest floor, his nose practically resting on the edge of the trench, and growled, smiling, “Ah! You must look with fox’s eyes.”