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Forest Types in Northeast India | Classification | UPSC, APSC

Northeast India is rich in various types of natural vegetation. Climate, physiography, and soils of the region have provided favorable conditions for the growth of natural vegetation.

The northeast region of India supports almost all types of vegetation from cultivated plains to grasslands, meadows, marshes, swamps, scrub-forests, tropical forests, temperate forests and alpine vegetation.

The region has one of the heaviest rainfalls in the world. Although the average annual rainfall of the region is about 250 cm, it varies from place to place. The altitude variations from 200-5000 m and the presence of deep valleys, hills provide a range of ecological variations thereby producing different types of climatic conditions from warm subtropical in the foothills, moderate in the middle and cool temperate in high hills, which determine the vegetation pattern of this region

Forest of Northeast India may be broadly classified into 1. Tropical forest, 2. Subtropical forest, 3. Temperate forests, 4. Sub-Alpine forests and 5. Alpine forests.

Alpine forest

Forest Types in Northeast India

1. Tropical forest
    1.1 Tropical evergreen and semi-evergreen forests
    1.2 Tropical dry and moist deciduous forest 
    1.3 Tropical grassland
2. Subtropical forest
    2.1 Subtropical mixed forest
    2.2 Sub-tropical pine forests
    2.3 Sub-tropical to temperate grassland
3. Temperate forests
4. Sub-Alpine forests
5. Alpine forests

1. Tropical Forest

Tropical forests confine up to an elevation of 1000 m altitude with heavy rainfall and humidity and are highly rich in floral diversity. Depending upon the location and degree of precipitation they are broadly discussed bellow

1.1 Tropical Evergreen and Semi-Evergreen Forests

Those parts of the region where average annual rainfall is more than 200 cm and temperature 250 C, there grow tall trees with evergreen foliage.

Such forests with an average rainfall coupled with high the relative humidity are confined to the foothills of Sikkim, Arunachal Pradesh comprising of Kameng, Subansiri, Lohit, Tirap district, Assam valley, parts of South Kamrup district and Narduar reserved forest in Sibsagar district, Kakoi and Dulong reserved forest in North Lakhimpur district, parts of Cachar district, the western and northwestern parts of Nagaland and Manipur forest areas adjacent to Burma, Southern and northern slopes of Meghalaya and Dharamnagar, Kaiiashahr, Beionia and Sadar Sub-division of Tripura. It also covers the forests of Bamihat and Umtru.

The common plants of the tropical evergreen forest of this region are Nahar, Halong, Hallock, Makari Sal, Titachampa, etc.

1.2 Tropical Dry and Moist Deciduous Forest

This forest found in the areas where the average annual rainfall is 80 cm to 200 cm.  The tropical moist and dry deciduous forests remain dry period from December to March.

These types of forests are confined in parts of Goal para, Nowgoan, Darrang and Kocharigaon in Assam, northern slopes of Meghalaya, northern and northwestern parts of Garo hills, Amarpur, Sonamura, Dharamnagar, Belona, Udaipur and Sadar subdivision in Tripura, northern sides of the forests areas of Kawnpuri, Hortaki, Bhairabi, Kolarib, Vairentee and western part of Mizoram bordering Tripura etc.

The common species of tropical deciduous plants are Sal, Teak, Gamari, Simul, khoir, Elephant Apple. Economically the most important products of the deciduous forest are Sal and Teak.

1.3 Tropical Grassland

Grassland is not uncommon in Northeast India. However, most of the grasses of the region, except the alpine grass of high altitude in the Himalayas, are not climogenic. There are several factors associated with the production of this grassland.

Some of this grassland grow because of the original forests were earlier destroyed for shifting cultivation. There are tall grasses in Tarai region of Brahmaputra valley, due to the ground always remain saturated with water and hence tall trees do not grow.

The sandy Charland's (River Bank) are normally can’t support tall trees but can grow seasonal grasses.  The swamp’s and marshes support swamp vegetation which includes mostly grasses.

2. Subtropical Forests

The subtropical forest has a cooler and humid climate and found in altitude of 1000 to 2000 meters.

2.1 Sub-Tropical Mixed Forests

These forests with an annual rainfall of 150 - 400 cm are evergreen and semi-evergreen type with enormous diversity being confined to the hilly regions of Assam slopes of Meghalaya, Koupru hills, Nongmaijing areas bordering to Myanmar (Burma), Manipur and Mizoram and Patkoi ranges in Nagaland etc.

Some of the important timber species in this type are – Koroi (Abelmoschus), Pomas (Chukrasia), Sopas (Magnolia), Gamari (Gmelina), Hollock (Terminalia), Sam (Betula nigra), Am (Mangifera), Badam (Prunus), Betula and Alseodaphne petiolaris (Ban-hanwalu), Antidesma bunius, Betula alnoides, Cleidon speciflorum etc. Higher up pure stands of Pinus kesiya(Khasi-pine)

2.2 Sub-Tropical Pine Forests

The subtropical pine (Pinus kesiya) forests cover an extensive area between 800 and 2000 m altitude in all the hilly states of northeast India. They have come to stay as a fairly stable community and have not been succeeded for a long period of time by the subtropical broad-leaved primary forests, which represents the climax formation of the area.

These forests with moderate rainfall occupy the areas in the Khasi and Jaintia Hills of Meghalaya (Jowai, Pynursla, Cherrapunjee and Nongstoin areas) as well as Rupa valley in the kameng district of Arunachal Pradesh, Ukhrul, eastern and southeastern parts of Tuensang and Phek districts in Nagaland, Mao and Sugnu areas in Manipur, hilly tracts around Champhai Northial and Phawngpui in Mizoram

Pinus kesiya is the most dominant species in the Khasi and Jaintia Hills whereas Pinus wallichiana is found in the Rupa valley area along with Berberis, Rhododendron arboreum, Quercus griffitthii and members of Rosaceae and the presence of large areas of Chir pine in Arunachal Pradesh

2.3 Sub-Tropical to Temperate Grassland

The grasslands wherever present are a biotic climax due to removal of original forest cover. The rolling grasslands around Nongstoin, Mawsynram, Mawphlong, Mawsmai, Cherrapunjee, Jowai, Haflong and major parts of Garo hills in Meghalaya, Ukhrul in Manipur etc.

3. Temperate Forests

The type of vegetation is found in the altitudes ranging from 2000 to 3500 m and is confined to small pockets along the southern slopes of the Khasi and Jaintia hills, especially the sacred groves viz. Shillong peak, Law Lyngdoh at Mawphiang and Lawkyntang at Mawsmai etc.

The sacred groves largely fall under this category and are the relic type evolved through millions of years. The common trees are Lithocarpus fenestratus, Castanopsis kurzii, Quercus griffithii, Q. semiserrata, Schima khasiana, Myrica esculenta, Symplocos glomerata, Photinia arguta, Ficus nemoralis, Manglietia caveana, Acer spp., Exbucklandia populnea, Engelhardtia spicata, Betula alnoides, Rhododendron arboretum, etc.

Shrubs include Mahonia pycnophylla, Daphne papyraceae, Polygala arillata, Camellia caduca, Rubus spp., etc.

These forests are exceptionally rich in epiphytic flora comprising Ferns, Lichens, Mosses, Orchids, Zingibers, etc.

4. Sub-Alpine Forests

This type of vegetation is confined to higher ranges of Himalayas. Ranges surrounding Thangu, Yumthang, Sandakphu, Changu and Kapup areas in the Sikkim Himalayas and higher ranges of Lohit in Arunachal present; Saramati and Japvo hills in Nagaland; Chingsaw, Japvo, Kowpur, Shiroy and Somra hill ranges of Manipur.

Alpine shrublands, characterized by rhododendrons, predominate at lower elevations, close to the treeline. The rhododendron flora of the ecoregion is quite varied, with species composition changing as one moves from west to east along with the range.

This subalpine type of vegetation is associated with shrubby and bushy species of Abies densa, A.spectabilis Berberis, Betida utilis, Cotoneaster, Cypressus torulosa, Juniperus, Lonicera, Picea spimdosa Rhododendron, Salix, and a few others. In the spring and summer, the alpine meadows are covered with brightly colored flowers.

5. Alpine Forests

Although Northeast India falls within the relatively low latitudes, It has high Himalayas where the temperature is low.

Vegetation from the sub-alpine region gradually merges with complete disappearance of tree growth into the alpine type as the altitude increases from 4500 m up to 5000 m, which is more or less the limit of plant life.

The vegetation is known as alpine grass. Apart from various species of grass,  it also contains some varieties of juniper, rhododendron, shrubs and mosses.

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