In general, the forest is defined as a piece of land that is thickly covered with trees. Forest is also known as woods or woodlands. They cover approximately 30% of land and 9.4% of the entire planet Earth.
Forests supply us fruits, timber, medicines in huge quantities besides they also act as large purifiers of airs, by absorbing carbon dioxide and giving out oxygen.
There are three main types of forests based on latitude – tropical, temperate and boreal forests.
Tropical forests
They occur near the equator, between 23.5 degrees N latitude and 23.5 degrees S latitude. They are characterized by the highest diversity of both flora and fauna, especially insects and flowering plants. This incredible amount of biodiversity accounts for 50 to 80 percent of the world’s plant and animal species.
Another important characteristic of tropical forests is their distinct seasonality: winter is absent, and there are only two seasons (rainy and dry). The length of daylight is 12 hours and varies little.
- Precipitation is evenly distributed throughout the year, with annual rainfall exceeding 100 inches.
- Soil is nutrient-poor and acidic. Decomposition is rapid and soils are subject to heavy leaching.
- Canopy in tropical forests is multilayered and continuous, allowing light to penetrate.
- Flora is highly diverse; one square kilometer may contain as many as 100 different tree species. Trees are 25-35 m tall, with buttressed trunks and shallow roots, mostly evergreen, with large dark green leaves. Plants such as orchids, bromeliads, vines, ferns, mosses, and palms are present in tropical forests.
- Fauna includes numerous birds, bats, small mammals, and insects.
Further subdivisions of this group are determined by the seasonal distribution of rainfall:
- evergreen rainforest: no dry season
- seasonal rainforest: a short dry period in a very wet tropical region (the forest exhibits definite seasonal changes as trees undergo developmental changes simultaneously, but the general character of vegetation remains the same as in evergreen rainforests)
- semi-evergreen forest: a long dry season (the upper tree story consists of deciduous trees, while the lower story is still evergreen)
- moist/dry deciduous forest (monsoon): the length of the dry season increases further as rainfall decreases (all trees are deciduous)
Temperate forests
Temperate forests are common throughout North America, Western Europe, and Northern Asia. They are primarily deciduous characterized by tall, broad-leaved hardwood trees that shed brilliantly colored leaves each fall. Well-defined four seasons with a distinct winter characterize this forest biome. The moderate climate and a growing season of 140-200 days during 4-6 frost-free months distinguish temperate forests.
- Temperature varies from - 30°C to 30°C.
- Leaves fall off trees and nourish the soil; therefore, the soil is fertile and enriched with decaying litter.
- Canopy is moderately dense and allows light to penetrate, resulting in well-developed and richly diversified understory vegetation and stratification of animals.
- Flora is characterized by 3-4 tree species per square kilometer. Trees are distinguished by broad leaves that are lost annually and include such species as oak, hickory, beech, hemlock, maple, basswood, cottonwood, elm, willow, and spring-flowering herbs.
- Fauna is represented by squirrels, rabbits, skunks, birds, deer, mountain lion, bobcat, timber wolf.
Further subdivisions of this group are determined by the seasonal distribution of rainfall:
- moist conifer and evergreen broad-leaved forests: wet winters and dry summers (rainfall is concentrated in the winter months and winters are relatively mild).
- dry conifer forests: dominate higher elevation zones; low precipitation.
- mediterranean forests: precipitation is concentrated in winter, less than 100 cm per year.
- temperate coniferous: mild winters, high annual precipitation (greater than 200 cm).
- temperate broad-leaved rainforests: mild, frost-free winters, high precipitation (more than 150 cm) evenly distributed throughout the year.
Boreal forest (Taiga)
Boreal forests, or taiga, represent the largest terrestrial biome. The word ‘Boreal’ means northern, these forests are occupying about 17% of the land. Occurring between 50 and 60 degrees latitudes, boreal forests can be found in the broad belt of Eurasia and North America with two-thirds in Siberia and the rest in Scandinavia, Alaska, and Canada. Seasons are divided into short, moist, and moderately warm summers and long, cold, and dry winters. The length of the growing season in boreal forests is 130 days.
- Temperatures are very low.
- Precipitation is primarily in the form of snow, 40-100 cm annually.
- Soil is thin, nutrient-poor, and acidic.
- Canopy permits low light penetration, and as a result, the understory is limited.
- Flora is dominated by cold-tolerant evergreen coniferous trees with needle-like leaves, such as pine, fir, and spruce. The needle-like leaves have a minimal surface area to prevent excessive water loss.
- Fauna includes woodpeckers, hawks, moose, bear, weasel, lynx, fox, wolf, deer, hares, chipmunks, shrews, and bats.
