The Web of Forest Life
The organisation of a forest is much like that of a large city, as an examination of the Great Smoky Mountains National Park of Tennessee and Northern Carolina illustrates. It includes the largest virgin forest in the Eastern United States. In it flourish more than 100 species of trees, all native to Europe. The skyscrapers of this forest city are its dominant trees, some of which soar 30 to 46 metres above ground -yellow poplar, basswood, sugar maple, buckeye, hemlock, and yellow birch. Beneath these giants, an understorey of smaller trees, equivalent to a city's larger apartment buildings -magnolia, holly, and others fills in the skyline. Nearer the grounds are the small apartment buildings -a layer made up of rhododendron, hydrangea, and vibumum that send puffs of bloom through the forest alleys. The private homes and shops can be compared to the approximately 100 species of herbs that cling to the forest floor. This lowest layer is a miniature in itself, with a canopy of spreading herbs and ferns and undergrowth of smaller plants.
The Great Smoky Mountains National Park is organised into eight layers -the soil basement, the forest floor, low herbs, high herbs, shrubs, low trees, tall trees, and the air above the forest canopy. The organisation of tropical rainforests is infinitely more complex; in some, the vegetation is arranged in as many as 27 groupings.
Trees are the pillars upon which much of the other forest life is draped. They create unique conditions for life, and one clearly sees this if he walks the few yards from a field into a forested area. The soil in the field is dry and unyielding, while the forest floor is moist and springy. It is much darker in the forest as most of the sunlight is absorbed by the leaves, or reflected, and only less than 1% of the light reaches the forest floor. In summer, the field is hot and windy, but the forest is cooler and the wind's velocity is only one-tenth of that outside the forest. During the showers, the canopy will intercept much of the rain and the leaves will be thoroughly wetted, but less than half of it will reach the ground.
Left: The undergrowth of the rainforests might be gloom and sullen, but within this crowd of decaying leaves, as an observant one can actually spot the bursting leaf-ltter community.
All life in a forest is intimately connected with other life in a chain of relationships, which begins with the sun. Only green plants can convert sun power into stored chemical energy and originate the food cycle through every living thing in the forest. This stored energy is transferred into other forms when the animals consume the plants. These animals in turn become the food supply for other predators. When the animals die, they decompose and return the nutrients back to the soil, so that green plants can absorb them through their roots and continue the nutrient circulation in the forest.
Normally, this web of inter-dependence has a great limit of stretch before it snaps. One members of the forest community may increase rapidly, thus presenting a threat to the forest, but magnitude of this threat is usually absorbed or reduced by other organisms in the web. However, there are also occasions where a slight change can restructure the whole forest community. In such an event, many forest trees might be destroyed, and the whole super-structure of life that took centuries to build up might perished with it. Man will ultimately feel the effects of the unraveling of the web, for he too is affected by the fate of the forest. The water that formerly sank into the sponge of forest soil now finds its way down the mountains with few barriers, adding to flood hazards and landslides.
Man is a member of the forest community, probably the most destructive one. The ringing sound of his axe and the crackle of his fires fills the air in anywhere with woods, until he has reduced much of the world's virgin forest to pieces of useless and impoverished land. A large area of tropical rainforest has been cleared to make way for the rubber and cocoa plantations. Now, even the indigenous humans who used to be living in harmony with the green Eden are now collaborating with outsiders to destroy their homelands. If the trend of adopting the technology to clear wide areas of forest goes on, then the forests and its inhabitants will one day be gone forever, and never to return again.