FORESTS: THREE MAJOR TYPES OF FORESTS

 

Forests are lands dominated by trees. The three main types of forest—tropical, temperate, and cold (northern coniferous, or boreal)—result from combinations of varying precipitation levels and varying average temperatures.

1. TROPICAL FORESTS:

Tropical rain forests are found near the equator, where hot, moisture-laden air rises and dumps its moisture. These lush forests have year around, uniformly warm temperatures, high humidity, and almost daily heavy rainfall. This fairly constant warm and wet climate is ideal for a wide variety of plants and animals. These forests are often called jungle, but that word refers to the thickest and most dense parts of a tropical rain forest. Tropical rain forests have a very high net primary productivity. They are teeming with life and possess incredible biological diversity. Although tropical rain forests cover only about 2% of the earth’s land surface, ecologists estimate that they contain at least half of the earth’s known terrestrial plant and animal species. For example, a single tree in these forests may support several thousand different insect species.

2. TEMPERATE FORESTS:

Temperate deciduous forests grow in areas with moderate average temperatures that change significantly with the seasons. These areas have long, warm summers, cold but not too severe winters, and abundant precipitation, often spread fairly evenly throughout the year. This biome is dominated by a few species of broadleaf deciduous trees such as oak, hickory, maple, poplar, and beech. They survive cold winters by dropping their leaves in the fall and becoming dormant through the winter. Each spring, they grow new leaves whose colors change in the fall into an array of reds and golds before the leaves drop. This biome has been disturbed by human activity more than any other terrestrial biome. However, within 100–200 years, areas cleared of their trees can return to a deciduous forest through secondary ecological succession.

3. COLD FORESTS:

Evergreen coniferous forests are also called boreal forests and taigas (“TIEguhs”). These cold forests are found just south of the arctic tundra in northern regions across North America, Asia, and Europe and above certain altitudes in the Sierra Nevada and Rocky Mountain ranges of the United States. In this subarctic climate, winters are long, dry, and extremely cold; in the northernmost taigas, winter sunlight is available only 6–8 hours per day. Summers are short, with cool to warm temperatures, and the sun shines up to 19 hours a day. Most boreal forests are dominated by a few species of coniferous (cone-bearing) evergreen trees such as spruce, fir, cedar, hemlock, and pine that keep most of their leaves year-round. Most of these species have small, needle-shaped, wax-coated leaves that can withstand the intense cold and drought of winter, when snow blankets the ground. Such trees are ready to take advantage of the brief summers because they need not take time to grow new needles. Plant diversity is low because few species can survive the winters when soil moisture is frozen. This biome contains a variety of wildlife. Year-round residents include bears, wolves, moose, lynx, and many burrowing rodent species.