Summer Rain

by William H. Amos, Vermont, US

 

Unlike last week's fierce storms, today's rain was gentle and brought to mind other times when soft rainfall was welcome and comforting. I opened a book I once wrote and found portions that tell what I still feel this pre-millennial July day thirty years later.

Assorted selections from THE INFINITE RIVER (Random House 1970):

Everywhere there was a whispering, as water, created of the earth, returned once more. Hour upon hour the rain descended, the abrupt arrival of each drop recorded when it struck ground or leaf, compressing the air in a sharp, fluid report. Small sounds radiated upward and outward, blending and losing all individuality, until to ears that heard, the forests and lower fields rustled with a pervading, welcoming murmur.

The rain created a luminous halo around the distant hills, but overhead there was only a scudding darkness. Haze in the treetops muted the color and outline of their foliage, and trees further away were only faint outlines and often totally obscured.

A raindrop, a million times the size of a cloud droplet, would have been a perfect, glistening sphere if surrounded by equal forces. But this could not be, for winds and changing pressures buffeted it so vigorously that its restraining surface film could hardly hold the water it contained, much less maintain the shape of a spheroid. As it began to fall, opposing pressures underneath cushioned its descent, causing the bottom to flatten out and even become concave, while the remainder billowed out above in a trembling, ballooning mass. When the drop flattened, it side-slipped, altered course, then again dropped straight down. Set in motion, a drop responded to both internal and external stresses until it oscillated and quivered like a living thing, alternating between a globule, a fat parachute, and a flattened disk.

A single drop, indistinguishable from its neighbors, collided and coalesced with other drops as it fell. Although it was repeatedly borne aloft again by the wind, its rate of descent, governed by its growing size, kept accelerating. When it struck a drop of similar size, both shattered into a spray of smaller droplets that began the falling and rising process over again. But the number of heavy drops increased, and soon many of them were clear of the cloud and fell directly to the earth.

Few drops struck the earth without previous interruption, but were intercepted by trees, shrubs, and low-lying grasses. When drops broke against leaves and splashed off, they multiplied into innumerable little droplets, causing the entire lower canopy of woodland to quiver as rain cascaded from above. Every seedling, every fern of the forest floor trembled in a rooted dance.

Leafy trees shed water quickly, but the evergreens, glistening with silver beads, held much of what they received between tightly spaced needles. Hemlocks displayed glassy spheres at the end of each of their tens of thousands of blunt needles. Heavy drops collected along fir branches, but left at drip points halfway along, falling to limbs below. Streams of water clung to the underside of maple branches in crystalline ridges. Every twig, every stem and branch in the forest was wet with a thin layer of moisture, and the entire film flowed steadily downward along the trunks until it entered the soil where it diffused outward through the loose, absorbent forest floor. Leaf mold covering the soil became a rich, dark-brown carpet thick with captured water.

Rocks jutting above the ferns turned a deep gray, and lichens encrusting their sides no longer were dusty and dried, but grew green as the algae within drank moisture. At the base of the rocks, the green of mosses deepened and grew richer, and the little plants straightened with water taken in through their delicate rootlike fibers. A cluster of reddish mushrooms glistened and swelled with succulence.

Whenever a large drop struck saturated soil, its compression created a little coronet of two dozen or more tiny spheres that shot into the air, then curved and fell spattering back, describing a dimpled circle around the original impact.

When each raindrop was finally stilled, its surface film immediately spread over soil particles and bits of vegetation, until every solid surface had stretched upon it an unbroken layer of water. Within the soil, water flowed quickly between grains of sand and earth and spread through countless galleries and internal spaces. Often it followed the hidden tracery of roots, filled the burrows of earthworms, and flooded the dwellings of ants, grubs, moles, and snakes.

Throughout the night the forested hills drank in the rain. After water had infiltrated leaf litter and loose organic soil at the surface, it sank below the deepest loam and encountered sand and gravel. All particles in the soil, organic or not, accepted a film of water that clung fast due to molecular forces operating between the particles and water. The soil had been loose with air passageways penetrating it, but now was becoming heavy and dense with accumulating water. Atmospheric gases, once plentiful in the soil, were diminishing. Some small subterranean lives tolerated the water, some welcomed it, but others drowned and suffocated from the lack of oxygen. A few crept into the rare air bubbles that remained, and were safe.

Not long after midnight the falling rain began to exceed the capacity of the soil to absorb it. Water accumulated on the surface as the overflowing ground refused it, then began to slip into small depressions to collect in shallow pools. Rivulets carried masses of brown fir needles to form miniature logjams, creating additional pools until the little dams gave way with a rush. As they broke and pools spilled over, their water joined other streams until—when the level of encircling retaining elevations was reached—sheets of water slipped like quicksilver down one gentle incline after the next.

When raindrops struck a pool's surface, small erect spouts jumped instantly from the point of impact. At the top of each spout, a tiny droplet broke free, shot higher into the air, and finally fell back to rejoin the bombarded puddle. Occasionally when a drop struck a puddle, a thin ring of muddy water arose, joined at the center, and trapped air in a large bubble which floated briefly until it was punctured by another raindrop.

Water deep within the soil moved slowly. It sank down, percolating through the loose earth, where it touched upon a multitude of tiny lives which depended upon its presence. As water dissolved soil minerals, new conditions of acidity, alkalinity, and electrical charge were established, conditions affecting most of the small earth-dwellers. Mechanisms in the cells of roots began their chemical pumps, not only bringing in water but using it as a medium for the transport of dissolved minerals across their cell membranes. Fungi and bacteria emerged from spores minutes after being surrounded by the seeping water.

Bacterial populations in the soil were changing. Those requiring oxygen were giving way to others that became active only when that element was absent. This cessation of activity was only temporary, and later when the water would seep away, the oxygen-users would begin their life processes again. Bacteria in the soil had many functions: some worked upon mineral compounds of sulfur, nitrogen, and iron; some broke down organic compounds in the process of decay; and a few affected the growth of plants by producing antibiotics. In turn bacteria were preyed upon by small soil animals, and attacked by virus-like bacteriophages, tiny motes which could destroy them completely by diverting a bacterium's own life processes. When conditions of moisture, temperature, and food supply became unfavorable, many soil bacteria would form resistant spores. At this moment in the wet earth, some bacteria were emerging from spores, while others were forming them.

Although many bacteria moved freely, their diminutive size prevented them from making headway against the slow currents of water flowing through the soil. By the billions they were carried from the surface to deeper strata, then horizontally as the ground water sought emergence at a lower level. No soil particle or interstitial space was without its own large and varied population of microbes.

Among the first animals to respond to saturation of the soil were microscopic one-celled protozoans: amoebas that crawled about carrying delicate urn-like cases into which they could retire; flagellates that would stay active until the last vestiges of water disappeared; dwarf ciliates speeding through water-filled spaces with thousands of synchronized beating cilia. Some of the protozoans fed upon organic matter, but the greatest number devoured living bacteria swarming in the soil water, swept down from surface layers of leafy debris.

Other grotesque creatures were present, scarcely larger than the soil particles they lived among. There were shiny, translucent, eight-legged mites creeping carefully about; omnipresent roundworms wriggled with increased activity now that the boundaries of their aquatic world had enlarged to a virtual infinity; water bears used four pairs of clawed legs to wedge themselves from one cavity to the next; and rotifers unfolded beating cilia to create a fluid vortex that swept into their beating jaws bacteria and one-celled plants suspended in the water.

From a rotten log, once nearly dried out, but now a moist and pulpy mass, a slug crawled from its slime cocoon that had prevented desiccation, and inched slowly toward the ground, leaving behind a cluster of glass-clear eggs. In the same log, a red-backed salamander crept through a tunnel excavated long ago by a wood-boring beetle. At the entrance the small lungless amphibian waited with staring, protruding eyes as rain-drops stirred the scene outside.

Across the forest floor small annual seed plants showed the effects of water absorption. Their delicate stalks grew turgid and straight, while their leaves flattened and extended stiffly into the night air. Each leaf was struck repeatedly by raindrops that fragmented and splashed in a fine spray about the plants. By absorbing soil water, woody shrubs and trees were making preparations for the following day when the sun's energy would set into motion a vast and complex system of water transport within their trunks, ultimately releasing individual water molecules to the atmosphere by evaporation.

There was no single fate for the water that fell to earth during the night. What happened to a raindrop was determined by chance at the moment of impact. Some water seeped into the soil and flowed parallel to the surface, only to emerge as a spring farther down the hillside. Other drops continued to sink into the soil until they were trapped beneath deeply buried layers of rock. Under such an impervious ceiling the filtered water would continue to flow very slowly, taking a thousand years or more until it broke free of its confinement under a distant sea.

The rain stopped in the early morning hours, but the murmuring of water dripping from millions of leaves went on, gradually diminishing. When it finally ceased, a heavy silence blanketed the forest. A single delayed drop, hesitating, plunged into a still pool below and broke the quiet with a sharp musical note.

A screech owl clung to the lip of a hole high in a dying oak, fluffed out its feathers and shook off a fine spray of moisture. It looked about attentively, gave its wavering, chuckling cry, and launched itself into the dark. One last nasal call of a spadefoot toad signaled the completion of its night of activity, and it joined others of its kind beneath the wet soil. In the distance, a grayness foretold the end of night.

The sun rose in a cleared sky and illuminated mist clinging to the wet mountain slopes. Every tree and bush, all grasses and ferns, spider webs, rocks, and the soil itself, gleamed with refractive liquid jewels that caught miniature images of the sun and focused them back into the sky. Against the silence, calls of birds poured out.

Comments to the author Comments to the author sent via our contacts page quoting page url plus : ('wamos','')">Bill Amos welcomed.

1970 & 1999 William H. Amos

Bill Amos, a retired biologist and frequent contributor to Micscape, is an active microscopist and author. He lives in northern Vermont's forested hill country colloquially known as the Northeast Kingdom, and takes delight in studying the several ponds on his land.

(Images by David Walker, Fuji DX-10 digital camera).

Editor's note: Other articles by Bill Amos are in the Micscape library (link below). Use the Library search button with the author's surname as keyword to locate them.

 

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Published in the July 1999 edition of Micscape Magazine.

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