THE ATOMIC INTERCHANGE
The line between the end and the beginning is sometimes hard to discern, like the line separating the sand from the sea. They seem to run together for a while, and what we think is an ending often becomes a new beginning. — Bill Gaither
All things in Nature are neutral when it comes to any kind of human valuation. Nature has only intrinsic value in that each component of a forest or an ocean—be it a microscopic bacterium, a towering 800-year-old tree, or a huge whale—is allowed to develop its prescribed structure, carry out its prescribed function, and interact with other components of the ecosystem through their prescribed, interdependent processes and feedback loops. No component is more or less valuable than another; each may differ in form, but all are complementary in function—whether on land or at sea.
Consider that an ancient tree rotting in a forest and a whale decomposing on the floor of an ocean are re-investing the borrowed constituents of their bodies in the long-term productivity of their respective ecosystems. Here, they are entering the atomic interchange, where the shared biological capital, vested in timeless atoms, is borrowed and given up, only to be on loan again. Each atom represents the cosmic currency endlessly used in the long corridors of time. Today, an atom may be part of the whale dead on the deep-ocean floor. In the far memory of the Universe, it may have comprised a bit of enamel on the tooth of a Tyrannosaurus rex. In a dream of the future, it may grace the iridescence of a South American butterfly or the throat of a Nepalese sunbird.
THE ATOMIC INTERCHANGE IN A FOREST
When one tugs at a single thing in nature, he finds it attached to the rest of the world. — John Muir
It's critical, at this juncture, to understand that vegetation in a forest both invests and re-invests biological capital into the ecosystem when it dies. I say this because vegetation not only uses elements from the soil as nutrients but also converts energy from the sun via photosynthesis in order to grow. The elements (old energy) are re-invested into the soil when a plant dies, whereas the energy captured from the sun (newly accumulated energy) is invested in the soil for the first time.
A tree may die standing, only to crumble and fall piecemeal over decades to the forest floor, or it may fall directly to the ground as a whole tree. Regardless of how it dies, the standing dead tree and fallen tree are only altered states of the live tree, which means that the large, live old tree must exist before there can be a large standing dead tree or a large fallen tree.
How a tree dies is important because its manner of death determines the structural dynamics of the habitat its body provides. Structural dynamics, in turn, determine the biochemical diversity hidden within the tree's decomposing body as ecological processes incorporate the old tree into the soil from which young trees must grow.
The falling of the ancient tree forever alters the forest in which it lived and starts an irreversible chain of events that can last for centuries. This "time lapse" is due in part to the character of the available wood, which varies greatly in different parts of the tree. Proteins are concentrated in the living tissues (the inner bark). Carbohydrates are concentrated in the dead woody tissue. The living inner bark is more easily digested than is sapwood, but moist sapwood is more digestible than is the drier heartwood. Each portion of a fallen tree therefore supports a characteristic group of insects adapted to a specific microhabitat. The numbers of any one species are regulated by the quantity and quality of their food supply. Inner bark furnishes the most nutritious food. The area of next greatest importance is the sapwood, then the heartwood, and finally the outer bark.
First bark beetles and then wood-boring beetles take up residence within a newly fallen tree. When wood-boring beetles penetrated a fallen tree and begin to thrive within it, Nature's system of checks and balances is also activated. At first, this system is composed primarily of predaceous beetles. In Douglas-fir, for example, adult red-bellied checkered beetles prey on the adult bark beetles, and larval checkered beetles prey on larval bark beetles, which helps keep bark-beetle numbers in check.
During the tree's first two years on the ground, an ever-changing variety of animals use it for shelter, food and foraging, and as perches. And throughout each year, the surrounding vegetation continues to grow and change, gradually adding another dimension of ever increasing diversity to the fallen tree.
When a large tree falls, it creates a notable hole in the forest canopy. Without further disturbance, the increased light striking the ground will "release" the shade-tolerant understory trees to grow and, in time, fill the hole. (Shade-tolerant means that a plant can survive in the shade of another plant; when the shade is removed, however, the plant responds with increased growth.) The extent of an opening can be increased considerably if a falling tree starts a domino effect—the successive uprooting and breaking of neighboring trees. The probability of a tree initiating a domino effect increases as the size and vigor of the falling tree increases. A large, intact tree is more likely to knock over the trees it strikes as it falls than is a decayed snag (a standing dead tree), even a large one. A snag will most likely break or shatter when hitting a large tree, but it may knock down a small tree if it strikes the tree directly.
Understory vegetation is either covered by a falling tree or crushed by it. Regardless, it is ultimately killed by injury or dies from lack of light. Vegetation may also be uprooted or buried by soil as a tree's roots are pulled from the ground. In addition, falling trees create opportunities for new plants to become established. For example, the bare mineral soil of the root pit and mound presents habitats that can be readily colonized by tree seedlings and other plants. (Pit refers to the hole left as a tree's roots are pulled from the soil, and mound refers to the soil-laden mass of roots, termed "rootwad," suddenly projected into the air above the floor of the forest.) With time, the body of the fallen tree itself becomes an ever-changing mosaic of habitats.
There are many scenarios in the response of ground vegetation to the falling of a tree because each tree falls differently, further compounded by the tree's size, species, and health, as well as characteristics of the surrounding forest. It is likely that understory vegetation, both existing and potential, will be released when a large tree falls because of the large opening created in the canopy that admits light to the floor of the forest. There is also space and resources for plants to become established and grow: first on the mineral soil of the newly exposed rootwad; second on the fallen tree itself; and third as the trunk decays, which allows plants to become established in the wood under the bark.
A newly fallen tree interacts only passively with the surrounding forest because its interior is not accessible to plants and most animals. But once fungi and bacteria, which are smaller than the wood fibers, gain entrance, they slowly dissolve and enter the wood cells, and wood-boring beetles, carpenter ants, and termites chew their way through the wood fibers. Meanwhile, many other organisms, such as plant roots, mites, springtails (also called collembolans), amphibians, and small mammals, must await the creation of internal spaces before they can enter. The flow of plant and animal populations and communities, air, water, and nutrients between a fallen tree and its surroundings increases as the tree's decomposition process continues. For example, the water-holding capacity of a large fallen tree varies by day, season, year, decade, and century, adding yet another dimension of diversity to the forest.
Surface area develops within a fallen tree through biophysical processes. A tree cracks and splits when it falls and then dries. Microbial decomposition breaks down the cell walls and further weakens the wood. Wood-boring beetle larvae and termites tunnel through the bark and wood, not only inoculating the wood with microbes but also opening the tree to colonization by other microbes and small invertebrates. Wood-rotting fungi produce zones of weakness, especially between the tree's annual growth rings, by causing the woody tissue laid down in spring to decay faster than that laid down in summer. Plant roots that penetrate the decayed wood split and compress it as the roots elongate and thicken in diameter. Because of all this internal activity, the longer a fallen tree rests on the forest floor, the greater the development of its internal surface area. Most internal surface area results from biological activity, the cumulative effects of which not only increase through time but also result from synergistic feedback loops—insect activity promotes decomposition through microbial activity that encourages the establishment of rooting plants that use the stored nutrients in the old tree as though it was Nature's grocery store.
Fallen trees thus offer myriad organisms multitudinous external and internal habitats, which persist through the decades, even as they change. Yet, the casual observer might notice only a few mushrooms or bracket fungi. These structures, however, are merely the fruiting bodies produced by mold colonies that run for miles within the tree. Many fungi fruit within the fallen tree, which means they are seen only when the tree is torn apart. Even then, only a fraction of the fungi present might be noticed because the fruiting bodies of most appear for but a short time. The smaller organisms, not visible to the unaided eye, are also crucial components of the forest. We humans do not begin to grasp the notion that microbes and fungi change a forest just a surely as a raging fire, only inconspicuously and more slowly. Theirs is an unseen function that is just as critical, and just as great as any in the forest. We are awed by a towering fir but not by a lowly bacterium and fungus, and yet, it's these humble organisms that largely convert a fallen tree into soil—and eventually into a new forest.¹
THE ATOMIC INTERCHANGE IN AN OCEAN
Nothing is wasted in our seas; every particle is used over and over again, first by one creature, then by another. In the spring, our ocean waters are deeply stirred and bring to the surface a rich supply of minerals ready for use by new life. — Rachel Carson
Not surprisingly, the communities that arise when a whale dies (such as the female California gray whale in the first photograph) and sinks to the bottom of the ocean display underwater versions of the classical stages of succession and change seen in terrestrial ecosystems. But instead of grasses and forbs giving way to shrubs, which yield to trees that mature into a forest, dead whales first nourish such scavengers as hagfish, then bone-eating zombie worms, and eventually clams, which use inorganic chemicals for sustenance.
In this first stage (which some researchers term the "mobile-scavenger stage") a whale is largely intact, but has hundreds of hagfish feeding on it. These eel-shaped fish, each about sixteen inches long, use their sharp, rasping teeth to scrape bits of meat off the carcass. They also grip a whale with their mouths, tie themselves in a knot, and use their bodies to loosen chunks of flesh. In addition, Pacific sleeper sharks grab the whale and twist their whole bodies back and forth, back and forth, until they finally rip off a piece of flesh (shark bite on the California gray whale).
In all, some 38 species of scavengers have been observed in an open feast during this stage, and they do a good job, when you consider that a whale's soft tissue accounts for approximately ninety percent of its weight. In fact, one whale, which weighed just over a ton (about 2,200 pounds), had the bulk of its flesh devoured in less than eighteen months.
The second or "enrichment opportunist stage" is composed of smaller organisms scavenging the "leftovers." These secondary scavengers include snails, amphipods that look like shrimp, and segmented worms. Around one whale, which had been on the ocean bottom for almost two years, every 1.2 square yards of sediment hosted as many as 45,000 individuals, which says nothing about the microbes.
At times, huge-celled bacteria form long filamentous lines that appear to the naked eye as a pale bacterial mat, which looks like it had snowed. There is also a segmented worm, affectionately called "snowboarding worm," that leaves a trail as it eats its way through the bacterial mat. In addition, many other segmented worms, called "polychaetes" (polys = Greek for "many" + chaet = New Latin for "bristle"), show up during this second stage. Although related to earthworms, those species that congregate around whale carcasses are much more diverse than their terrestrial cousins.
Finally, there are bone-eating "zombie worms," which get their nutrition by sending a tangle of green, root-like coils into the whales bones. Inside of this green tangle reside rod-shaped bacteria that break down the complex, organic compounds of which the whale's skeleton is composed.
When the hordes of wee creatures have reduced the whale to nothing but a pile of bones, the third stage begins, which is termed the "chemoautotrophic stage" ("chem" from the Greek chemikos = "of or pertaining to juices," + "auto" from the Greek autos = meaning "self," + "troph" from the Greek trophos = "one who feeds"). Many of the larger organisms that comprise this stage carry their own sulfide-metabolizing bacteria, such as the vesicomyid clams (vesicoz, which is Latin for "bladder" + mydos, which is the Greek word for "decay"). These clams don't eat in the usual sense, but rather get their nutriments from sulfide-metabolizing bacteria that live in their gills. There is also a species of mussel that can amass a population of more than 10,000 individuals on the skeleton of a single whale, in addition to which there is a species of polychaete worm, which forms such dense colonies around whale skeletons they resemble lawns of "orange grass."
The fourth and final stage is called the "reef stage," because, with the nutritional component exhausted, the community shifts to undersea animals that require craggy structures as habitat. At this point, a whale's skeleton acts much like anchorage.
The carcass of a whale settling to the ocean bottom offers as much food as would normally be delivered by the regular rain of detritus in 2,000 years. Moreover, some whale carcasses in the third stage are still bristling with chemoautotrophs after seventy to eighty years of resting on the deep-ocean floor.²
In sum, what goes on inside and around the decomposing body of a dead tree or whale is the hidden biological and functional diversity. That trees become injured, diseased, die, and fall to the forest floor is therefore critical to the long-term structural and functional health of the soil, and so the forest. The forest, in turn, is an interactive, organic whole defined not by its respective parts, but rather by the interdependent functional relationships of those parts in creating the whole—the intrinsic value of each piece and its complimentary function. The counter part of a fallen tree is the sunken body of a dead whale slowly decomposing for nearly a century, while it enriches the deep ocean. These processes are all part of Nature's rollover accounting system—which count as both investments and re-investments of biological capital in the Nature's health plan mediated, as it were, through the atomic interchange.
We are all travelers. From 'birth till death' we travel between the eternities. — Anonymous
The foregoing discussion is based on: (1) Chris Maser and James M. Trappe, (Technical Editors.) 1984. The Seen and Unseen World of the Fallen Tree. USDA Forest Service General Technical Report PNW-164. Pacific Northwest Forest and Range Experiment Station, Portland, OR. 56 pp., (2) Chris Maser. 1989. Forest Primeval: The Natural History of an Ancient Forest. Sierra Club Books, San Francisco, CA. 282 pp. (Reprinted in 2001 by Oregon State University Press, Corvallis, Oregon.), and (3) Chris Maser. 1999. Ecological Diversity in Sustainable Development: The Vital and Forgotten Dimension. Lewis Publishers, Boca Raton, FL. 402 pp.
The foregoing discussion is based on: Susan Milius. 2005. Decades of Dinner: Underwater Community Begins with the Remains of a Whale. Science News 167:298-300.
©chris maser 2007. All rights reserved.