Having secreted a mucus seal between the opening of their shells and the camel thorn, Egyptian desert snails cling to their resting places during the heat of the day. They leave their daily stations in the cool of the evening and forage during the night, only to re-anchor themselves with the rising sun. The white of their shells reflects some of the sun’s heat, thus helping to keep their bodies cool.
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 an ecosystem, whether a microscopic bacterium in the tropics, a desert snail, a hedgehog, or a towering 800-year-old tree, is allowed to develop its prescribed structure, carry out its prescribed function, and interact with other components of their respective ecosystems through their prescribed, interdependent processes and feedback loops. No component is more or less valuable than another; each may differ from the other in form, but all are complementary in function.
To add to the overall complexity, in a late-successional, indigenous forest, a live old tree eventually becomes injured and/or sickened with disease and begins to die. How the tree dies determines how it decomposes and reinvests its biological capital (organic material and chemical elements) back into the soil and eventually into the next forest.
A tree may die standing as a snag to crumble and fall piecemeal to the forest floor over decades, or it may fall directly to the forest floor as a whole tree. How a tree dies is important to the health of the forest because its manner of death determines the structural dynamics of its body as habitat. Structural dynamics, in turn, determine the biological-chemical diversity hidden within the tree’s decomposing body as ecological processes incorporate the old tree into the soil from which the next forest must grow. What goes on inside the decomposing body of a dying or dead tree is one example of the hidden biological and functional diversity that is totally ignored in a typical economic valuation of a forest. Consequently, that trees continue to become injured, diseased, and die is critical to the long-term biological health of a forest that itself is an interactive, organic whole defined not by the pieces of its body, but rather by the interdependent functional relationships of those pieces creating the whole—the intrinsic value of each piece and its complementary function.
A Douglas-fir in Oregon that was injured when its neighbor fell against it, and a white fir in Isen (Bavaria) West Germany that died of bacterial wet heart.
Regardless of how it dies, the snag and fallen tree are only altered states of the live tree; so the live large tree must exist before there can be a large snag or large fallen tree. A basic problem inherent in understanding this scenario lies in the fact that, if asked, few of the world’s leading scientists, legislators, policy-makers, or business executives could name the five classical Kingdoms of Nature (bacteria, fungi, algae, plants, and animals) or how they complement one another. This dearth of ecological literacy shows a basic lack of understanding how ecosystems and their self-reinforcing, ecological, feedback loops work, as well as a basic lack of understanding the long-term consequences of short-term political and/or economic decisions. Now comes an interesting belowground twist to the story of functional diversity. It is not only species of plants and animals that will become extinct with the liquidation of a late-successional forest; so too will the old “grandparent trees.” As crop after crop of young trees replace liquidated old trees, the ecological functions performed by the old trees, such as creation of the “pit-and-mound” topography on the floor of the forest with its mixing of mineral soil and organic topsoil, become extinct processes.1 Why? Because there are no more grandparent trees to blow over; yet, “windthrow,” which creates “blowdown,” is an extremely important event in forests, especially in such forests as those in southeast Alaska, where fire plays a minimal role in the disturbance regime, but windthrow is critical.2
A snag in the Cascade Mountains of Washington (left); a fungus that is slowly decomposing a tree in the Malaysian jungle (right); and a decaying European beech snag in Isen (Bavaria) West Germany (bottom).
“Pit” in pit-and-mound topography refers to the hole left in the forest floor as a tree’s roots are pulled from the soil, and “mound” refers to the soil-laden mass of roots, called a “rootwad” suddenly thrust into the air above the forest floor as the old tree topples. The young trees that replace the grandparent trees are much smaller and different in structure; so they cannot perform the same functions in the same ways. Of all the factors that affect the soil of the forest, the roughness of the surface caused by falling grandparent trees, particularly the pit-and-mound topography, is the most striking.
Uprooted trees enrich the forest’s micro-topography by creating new habitats for vegetation. They also provide opportunities for new plants to become established in the bare mineral soil of the pit and the mound. In addition, fallen trees open the canopy, allowing more light to reach the floor of the forest, that, in combination with the pits and mounds, creates and maintains a richness in the species of plants forming the understory and the herbaceous ground cover. As large trees fall, they bring with them nitrogen-rich lichens from the canopy to the forest floor, where the lichens decompose and add their nitrogen to the soil layer. With time, the fallen tree itself presents habitats that can be readily colonized by tree seedlings and other plants.
Club moss growing in and helping to decompose a fallen tree in northeastern British Columbia, Canada.
Extinction of the grandparent trees changes the entire complexion of the forest through time, just as the function of a chair is changed when the seat is removed. Theroughness of the forest floor that, over the centuries, resulted from the cumulative addition of pits, mounds, and fallen grandparent trees will become unprecedentedlysmooth—without pits and mounds, without large fallen trees.
Water moves differently over and through the soil of a smooth forest floor, one that is devoid of large fallen trees acting as reservoirs, storing water throughout the heat of summer, and holding soil in place on steep slopes. Gone are the huge snags and fallen trees that acted as habitats for creatures wild and free. Gone are the stumps of the grandparent trees with their belowground “plumbing systems” of roots hollowed out by rot that guided rain and melting snow deep into the soil.
This plumbing system of decomposing tree stumps and their large, deep, hollow roots frequently form interconnected, surface-to-bedrock channels that rapidly drain water from heavy rains and melting snow. As roots slowly rot away, the collapse and plugging of these channels forces more water to drain through the soil matrix, reducing its cohesion and increasing the hydraulic pressure, thereby increasing the probability of mass soil movements.
These plumbing systems cannot be replaced by the young trees of modern forests because their roots are too small and shallow to form the conduits necessary to rapidly move large quantities of water deep into the soil. Local extinctions of the ecological functions performed by grandparent trees, alive and dead, seems to pass unnoticed into the shadow-realm of bygone forests because their passing takes place in the “invisible present” of this eternal moment, which is all we ever have.
BIODIVERSITY—THE VARIETY OF LIFE
BIODIVERSITY—OUR ENVIRONMENTAL INSURANCE POLICY
Sunrise—a magnificent symbol of the commons and a new today.
Text and Photos © by Chris Maser, 2009. All rights reserved.