Thursday, July 21, 2011

Old-Growth Forest Ecosystems

Old-growth forests consist of trees that have never been cut so have never been forced to regrow. These primary forests contain the original growth of a tree population and therefore they contain the oldest and most mature trees found in the forest biome. Old-growth trees arise at the latest stage of forest ecological succession, and because of this they contain a mixture of species and a variety of sizes. They also contain dead trees that have fallen and begun to decay, broken branches, snags, and several canopy layers. All of these things create specialized habitats for a variety of animal life, plants, and fungi. Old-growth forests contain very complex ecosystems with many interrelationships between species, and of course, this enhances biodiversity.

The unique characteristics of old-growth forests sometimes provide habitat for species that cannot live anywhere else. Some of these specialized habitats include hollowed trees, tree cavities, decaying logs, the canopy, the understory, moist soil, and bark. In dense old-growth forests, the top of the canopy receives direct sunlight for the life in that habitat, while creatures near the forest floor live in dark, shaded surroundings. Animal diversity in old-growth forests includes moose, bear, weasel, lynx, fox, wolf, deer, bobcat, mountain lion, chipmunks, squirrels, shrews, bats, woodpeckers, owls, and hawks. This represents only a partial list and does not account for the microbes, insects, invertebrates, amphibians, reptiles, songbirds, and aquatic species that also live in old-growth forests. Vines, ferns, shrubs, mosses, lichens, and some grasses dominate the plant diversity. A typical old-growth forest in the Pacific Northwest contains giant redwoods, Douglas fir, spruce, and possibly hemlock and cedar. Each 2.5 acres (0.01 km) contain about 20 large trees at least 300 years old, many measuring over three feet (1 m) in diameter.

The health of an old-growth forest depends on fires caused by natural circumstances, such as lightning strikes. Frequent, short-lived ground fires reduce competing vegetation and degrade dead wood, which hastens the return of nutrients to the soil. Fires also thin out the densest growth and open more space for sunlight to reach places that had been cut off from light. Though fires may temporarily destroy some wildlife habitat, fires also create new habitat. For instance, some small mammals may prefer the plants and grasses that first break through the earth after a fire, and only ground fires afford this opportunity.

Old-growth forests and their ecosystems have remained largely a mystery despite the studies that have been conducted in them. They have outlived generations of humans, and they surely contain undiscovered species as well as ecosystems that have not been fully identified. These forests survived from a time when humans did not affect seemingly every corner of the Earth. For that reason alone, they deserve respect within the world of living things.

Source of Information : Green Technology Conservation Protecting Our Plant Resources

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