Types of Forests – Natural Vegetation
Forests are found around the world and around every corner of the earth. Forests play an important role in sustaining various species and deliver various benefits to both plants and animals.
Forests come in various types and sizes based on the climate and topography of those areas. Various types of forests fulfill diverse functions such as the production of wood, provide food to animals and plants, regulate water flow, protect soil, play a role in carbon fixation and store atmospheric carbon dioxide.
There are five types of forests:
1. Tropical Evergreen and Semi-Evergreen forests
2. Tropical Deciduous forests
3. Tropical Thorn forests
4. Montane forests
5. Littoral and Swamp forests
Tropical Evergreen and Semi Evergreen Forests
Tropical Evergreen Forests are found in the Western Ghats, hills of the northeastern region and the Andaman and Nicobar Islands. It grows exclusively on the wet, tropical side of Western Ghats.
On the other hand, Semi-Evergreen Forests grow in conjunction with moister grasslands and rocky plateau.
Found in warm and humid areas with annual precipitation of over 200 cm and mean annual temperature above 22oC.
Well stratified, with layers closer to the ground, and are covered with shrubs and creepers, with short structured trees followed by a tall variety of needs.
Trees reach great heights up to 60 m or above. There is no definite time for trees to shed their leaves, flower and fruition. As such these forests appear green all the year round. Species found in these forests include rosewood, mahogony, aini, ebony, etc.
The semi evergreen
The semi evergreen forests of eastern South Africa and Lesotho were formed by fires and they consist of a mixture of deciduous and evergreen trees. The undergrowth is made up of shrubs, ferns, herbs, creepers and saplings. Although the trees are not all evergreen some key components are.
For example the white cedar, holly, karroid or Satinwood are amongst the evergreens found in this type of forest. These trees have leaves that are needle like, flattened or awl shaped while conifers have scales to protect them from cold temperatures.
The British were aware of the economic value of the forests in India, hence, large scale exploitation of these forests was started. The structure of forests was also changed. The oak forests in Garhwal and Kumaon were replaced by pine (chirs) which was needed to lay railway lines.
Tropical Deciduous Forests
Understanding where tropical deciduous forests form and the climate changes associated with these regions is important because of the impact they can have on other ecosystems around them.
Tropical deciduous forests are located in a narrow range of latitudes. Those that occur below the equatorial region do not have a dry season, while those that occur above it do experience a mild dry season during part of the year.
These are the most widespread forests in India. They are also called the monsoon forests.
They spread over regions which receive rainfall between 70-200 cm. On the basis of the availability of water, these forests are further divided into moist and dry deciduous.
The Moist deciduous:
Moist deciduous forests are the mixture of trees and grasses. These forests are found in areas of moderate rainfall of 100 to 200 cm per annum, mean annual temperature of about 27°C and the average annual relative humidity of 60 to 75 per cent.
Forests are more pronounced in the regions which record rainfall between 100-200 cm. These forests are found in the northeastern states along the foothills of Himalayas, eastern slopes of the Western Ghats and Odisha.
Teak, sal, shisham, hurra, mahua, amla, semul, kusum, and sandalwood etc. are the main species of these forests. Dry deciduous forest — covers vast areas of the country, where rainfall ranges between 70 -100 cm. found in rainier areas of the Peninsula and the plains of Uttar Pradesh and Bihar.
Tropical Thorn Forest
A thorn forest is a dense, scrubland with vegetation characteristic of dry subtropical and warm temperate areas with a seasonal rainfall averaging 250 to 500 mm (9.8 to 19.7 in).
Thorn forests blend into savanna woodlands as the rainfall increases and into deserts as the climate becomes drier.
In the areas which receive rainfall less than 50 cm. These consist of a variety of grasses and shrubs.
It includes semi-arid areas of south west Punjab, Haryana, Rajasthan, Gujarat, Madhya Pradesh and Uttar Pradesh. Plants remain leafless for most part of the year and give an expression of scrub vegetation.
Montane Forest
Montane Forest is ecosystem found in mountains. It gets affected by colder climate at moderate elevations. In these areas dense forest are common. In Mountain Forest, rainfall and temperate climate leads to change in natural vegetation.
At higher elevations, temperate grasslands are common. Mountain forests can be classified into two types, the northern mountain forests and the southern mountain forests
The Himalayan ranges show a succession of vegetation from the tropical to the tundra, which change in with the altitude. Deciduous forests are found in the foothills of the Himalayas.
The southern mountain forest
The southern mountain forest is a tropical and semi-evergreen forest and is highly diversified with innumerable species of shrubs, herbs, grasses, creepers and trees.
These forests at the lower levels do not have tropic evergreen trees but they still show a diversity in flora and fauna.
This ecosystem differs from the northern tropical forests in several aspects such as altitude, rainfall, temperature and the types of species present in it.
As they are closer to the tropics, and only 1,500 m above the sea level, vegetation is temperate in the higher regions, and subtropical on the lower regions of the Western Ghats, especially in Kerala, Tamil Nadu and Karnataka.
The temperate forests are called 5holas in the Nilgiris, Anaimalai and Palani hills. Some of the other trees of this forest of economic significance include, magnolia, laurel, cinchona and wattle. Such forests are also found in the Satpura and the Maikal ranges.