(Environment & Ecology) TERRESTRIAL BIOMES - Equatorial Rain, Tropical Deciduous, Temperate and Boreal Forests



The world has been divided into following various Terrestrial Biome Types
Forest Biomes represent the largest and most ecologically complex systems. They contain a wide assortment of trees, plants, mammals, reptiles, amphibians, invertebrates, insects and micro-organisms which vary depending on the zone’s climate. Forest occupy approximately one third of Earth’s land area, account for over two-thirds of the leaf area of land plant, and contain about 70% of carbon present in living things. They are the major carbon sink and provide enormous amount of food and resources to the mankind.

1. Equatorial Rain Forest: This is found  in and around equator regions, characterised by ample heat and heavy rainfall throughout the year. The tree are very tall and of a great variety of species. The vegetation is so dense that little light reaches the forest floor. Most of the plants are evergreen, not deciduous.

Characteristic features:

  • The most outstanding feature is its great uniformity of temperature throughout the year to be around 28 oC with very little variation. There is no winter.

  • Cloudiness and heavy precipitation help to moderate the daily temperature, so that even at the equator, climate is not unbearable.

  • The diurnal as well as annual range of temperature is very small.

  • Well distributed annual rainfall of 150-250 cm having no distinct dry season, but having April and October as the maximum rainfall month.

  • Growing and flourishing season of trees in the forests are all round the year without any climatic extremities and hence no fixed pattern of seeding. Flowering, fruiting and decaying of trees.

  • Biodiversity is at its best in equatorial rain forests having ample varieties of flora and fauna. This is the reason for difficulty in commercial exploitation of timber.

  • Climbing plants, Epiphytes and parasites are innumerable.

  • A distinct layered arrangement with thick canopy at the top as all the trees and plants struggle for sunlight.

  • The smaller tree beneath form the next layer and the ground is rooted with ferns and herbaceous plants which can tolerate shades.

  • The hot, wet climate which stimulates rapid plants growth also encourages the growth of insects and pets thereby inflicting  many diseases and crop damage.

  • Soils of the equatorial rain forest are fairly due to thick layer of humus. But once the humus is used and the natural vegetative cover is removed, the torrential downpours soon washout most of the soil nutrients (leaching), making it useless for the agricultural purposes.

2. Tropical Deciduous Forest: These are found in the areas characterised by distinct dry and heavy wet seasons. The tress of tropical Deciduous forests lose all of their leaves in summer season to prevent loss of water. These forests have a more open and dwarfish composition, the trees being more stunted and widely spaced. In the dry season trees shed their leaves and the forest gives the appearance of vast grassland with naked trees, dispersed all over the region.

Characteristics features:

  • Such types of forests are found in the areas having distinct dry season and heavy concentration of rainfall within few months.

  • The areas have typical seasonality ranging from cool winters, hot and dry summer to rainy season.

  • Trees are normally deciduous, because of the marked dry periods, during which they shed their leaves to withstand the drought.

  • The forests are more open and less luxuriant than the equatorial forests and there are far fewer species.

  • Tropical deciduous forests yield valuable timber and are prized for their durable hardwood. For example- Teak, Sal, Acacia etc.

  • Bamboo thickets are other typical characteristics of such forests.

  • Areas of lesser rainfall exhibit Savannah and scrubland like feature with scattered trees and tall grass.

  • Majority of the forests have been cleared for agriculture to support excessive populations.

3. Temperate Forest These are found in areas with a milder, shorter winter season. This biome occupies the eastern half of the United States and a large portion of Europe. It is characterized by hardwood trees (e.g., beech, maple, oak, hickory) which are deciduous; that is, shed their leaves in the autumn. Canopy is moderately dense and allows light to penetrate, resulting in well-developed and richly diversified understory vegetation and stratification of animals.

  • The climate in the temperate forest varies, and the plant and animal life there must adapt. For example, when gets cold most animals put on an extra layer can get below warm.
  • The average temperature in this biome is 15 ᵒC in the daytime and in the night time it can get below freezing.
  • In every month of the year the Temperate Forest sees some rainfall. The rainfall ranges from 40 cm to 150 cm per year. Once in a while there are severe storms in this biome, and in some parts of the Temperate Forest it snows in winter months.
  • In the Temperate Forest there are generally warm summers, and short, cold and silent winters.

Trees and plants in temperate forests have special adaptations to survive in this biome. Deciduous trees are trees with leaves rather than pine needles, and they dominate temperate forests. As the seasons change each year, so do the leaves. Each year deciduous trees lose their leaves, and grow them back. In the summer their broad green leaves capture sunlight and help the trees make food through photosynthesis. As temperature cool in the fall, the chlorophyII (green pigment in leaves) breaks down, causing the beautiful red, yellow and orange leaf colours of fall. In the cold for them to protect their leaves from the damage of freezing in the winter, so they simply loose them and seal up the places where the leaves attach to the branch. The warmer spring days signal to the trees that they can grow new leaves again, and restart the cycle.

  • The Temperate Forest is full of various plants and trees. There are Pine Fir, Hemlock, Spruce, and Sequoias just to name a few.
  • Some plants are used to make medicines for people. Many plants flourish in this environment because of the rich soil that the Temperate Forest has.
  • The Temperate Forest has many different species of animals. There are bobcats, snow leopards, while tailed deer, raccoons, mice, and many types of birds just to name a few. Animals in the Temperate Forest depend upon one another in a complex food chain.
  • The soil in the Temperate Forest is very rocky, sandy, and is known to be mostly poor quantity.

4. Boreal forests (Taiga): Boreal forests, or taiga, represent the largest terrestrial biome. Occurring between 50ᵒ and 60ᵒ north latitudes, these can be found in the broad belt of Eurasia and North America: two-thirds in Siberia with the rest in Scandinavia, Alaska, and Canada. Seasons are divided into short, moist, and moderately warm summers and long, cold, and dry winters. Boreal Forests are dominated by conifers, especially spruces and firs. These are dotted with lakes, bogs, and marshes.

Characteristics features:

  • The Boreal forest is named after Boreas, the Greek god of the north wind.
  • The Boreal forest corresponds with regions of subarctic and cold continental climate.
  • There are long, service winters (up to six months with mean temperature below freezing) and short summers (50 to 100 frost free days), as is a wide range of temperature between the lows of winter and highs of summer.
  • There is little rainfall in the boreal biome. Precipitation comes in the form of fog and snow, with a little rain during the summer months.
  • Means annual precipitation is 40 cm to 50 cm but low evaporation rates makes this a humid climate.
  • This biome has dominant trees as needle leaf and coniferous (gymnosperm) trees.
  • The conical or spire-shaped needle leaf trees are adapted to the cold and physiological drought of winter and to the short-growing season.
    • The conical shape - promotes shedding of snow and prevents loss of branches.
    • Needle-leaf  - narrowness reduces surface area through which water mat be lost (transpired), especially during winter when the frozen ground prevents plants from replenishing their water supply. The needle of boreal conifers also have thick waxy coating a waterproof cuticle in which stomata are sunken and protected from drying winds.
    • Evergreen habit  -  retention of foliage allows plants to photosynthesize as absorb maximum heat from the sun and begin photosynthesis as early as possible.
    • Dark colour - the dark green of spruce and fir needles helps foliage absorb maximum from the sun and begin photosynthesis as early as possible.
  • Broadleaf deciduous trees and shrubs are members of early successional stages of both primary and secondary succession. Most common are alder birch, and aspen.
  • This type of forest supports very poor in biodiversity supporting only handful species of flora and fauna.
  • The trees of the boreal forest tend to have shallow roots, due to the thin soils.
  • Logging has played its role on the boreal forest, with large swaths of Siberia’s taiga harvested for lumber.
  • The soils of the boreal forest are often acidic, due to falling pine needle, and low on nutrients since the cold temperature do not allow much foliage to rot and turn into dirt.


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