Types of Soil and Natural Vegetation in India

SOIL #

Soil is the topmost layer of the earth’s surface. It consists of a mixture of minute particles of dis- integrated rocks, minerals, organic matter and bac- teria. Soil is formed when forces of nature such as temperature, rain, wind, waves, animals and plants act on rocks and break them into tiny pieces over a long period of time.

Soil consists of four layers. The first or topmost layer of soil is made up of minute soil particles and decayed plant and animal matter. This layer is vital for the cultivation of crops. The second layer is made up of fine particles like clay; the third layer is a combination of weathered basic rock materials and soil while the fourth layer consists of un-weathered hard rocks.

Each type of soil benefits different types of crops through their unique physical, chemical and biological properties. Alluvial soil is a fertile soil rich in potassium. It is highly suitable for agricul- ture, especially for crops such as paddy, sugarcane and plantain. Red soil has high iron content and is fit for crops like red gram, Bengal gram, green gram, groundnut and castor seed. Black soil is rich in calcium, potassium and magnesium but has poor nitrogen content. Crops like cotton, tobacco, chilly, oil seeds, jowar, ragi and maize grow well in it. Sandy soil is low in nutrient content but is useful for growing trees such as coconut, cashew and casuarinas in areas with high rainfall.

Soil Types and Distribution #

There are different types of soils in India and climate, altitude and composition of bedrock are the major factors that control the soil formation in India.

Disproportion in the annual distribution of rainfall in the country and excessive heat contribute char- acteristics to the soils of the country. Seven major types of soils in India are Alluvial soils, Black soils, Desert soils, Red and yellow soils, Saline soils, Lateritic soils and mountain soils.

1. Alluvial Soil: This is the most crucial and pervasive kind. It covers forty per cent of land area. In fact the complete Northern Plains are made up of these soils. They have been brought down and deposited by three enor- mous Himalayan rivers- Satluj, Ganga and Brahmaputra-and their tributaries. Through a tapered outlet in Rajasthan, they continue into the plains of Gujarat. They are common in eastern coastal plains, in the deltas of Ma- hanadi, Godavari, Krishna and Kaveri.

The river deposits extremely refined particles of soil, called alluvium in their plains during the path of their long travail, spread over hun- dreds of kilometres and thousands of years. These soils consist of diverse ratios of sand, silt and clay. They are prevalent in the coastal plains and deltas. As one moves further inland in the river valleys, the soil particles appear pretty heavier in size. In the upper reaches of the river Valleys, i.e. near the place of their origin, the soils are coarser. Such soils are more familiar in piedmont plains, i.e. those that are near the foot of mountains.

Soils are distinguished according to their age also. They are grouped in old alluvium and new alluvium types. The so called new alluvi- um may be even ten thousand years old. The old alluvium is called ‘Bhangar‘, and the new

alluvium is called ‘khadar’. The old alluvium often contains kankar nodules, with calcium carbonates in subsoil. The new alluvium is richer compared to the old.

Alluvial soils all together are exceptionally prolific. In general, they carry ample potash, phosphoric acid and lime. However, they are lacking in organic and nitrogenous substance. Soils in the drier areas are more alkaline. Al- luvial soils sustain over half the Indian popu- lation.

• Regur Soil/Black soil: Regur soils are black in colour and are also known as ‘black soils‘. Since they are perfect for growing cotton, they are also called cotton soils, in addition to their local terminology of ‘regur soils‘. These soils are most characteristic of the Deccan trap (Basalt) region, spread over the north- west Deccan plateau and are made up of lava flows. They cover the plateaus of Maharash- tra, Saurashtra, Malwa and southern Madhya Pradesh and continue eastwards in the south, along the Godavari and Krishna Valleys.

Black soils are made of exceptionally delicate that is clayey material. Owing to the high pro- portion of clay, Regur soils are sticky when wet and consequently, it becomes difficult to plough. They are well known for their ability to retain moisture. In addition, they are pros- perous in soil nutrients, like calcium carbon- ate, magnesium carbonate, potash and lime. They are usually poor in phosphoric content. They develop thick fissures in the field during hot weather. This helps in their ventilation; hence their self-ploughing eminence. This soil is viscous and unmanageable to work, unless tilled without delay, after the first or pre-monsoon showers.

Regur soils develop under semi-arid condi- tions specifically in the areas that are covered with basalt. In the southern region of Tamil Nadu, granites and gneisses with iron con- tent also form black soils under the required semi-arid climatic conditions. Regur soils are formed in Surat and Broach districts and also in the Narmada Valley and Tapti Valley. In these regions, humus is almost absent in the

soil and black colour of the soil is because of the presence of certain salts. In the hilly region of the country, Black soils are usually thin, poor and sandy.

Black soils or Regur soils are rich in lime and it is not unusual to find lime nodules deposi- tion under the layer of this type of soil. More- over, this soil is highly retentive of moisture and is highly productive particularly in the plains and along the river valleys where it is clayey and deep. It is said that the feature of retaining moisture in the soil is extremely useful. Thus, the deeper the soil, the larger is the amount of moisture held. However, ni- trogen which is considered as useful for the growth of plants is not sufficiently found in the Regur soil.

• Laterite Soil: Laterite soils are generally found capping the Indian flat uplands, and are spread in the western coastal region, getting incredibly heavy rain. Lateritic soils are also found in areas along the edge of the plateau in the east, covering small parts of Tamil Nadu and Orissa and a small part of Chhotanagpur Plateau in the north and Meghalaya in north- east. The soils are habitually poor and can hold only pastures and scrub forests. Among the mixed types of soils, two groups are more substantial. They include the desert soils of west Rajasthan and mountain soils of the Hi- malayas.

Laterite soils are mainly found in the tropical regions that receive heavy seasonal rainfall. High rainfall promotes leaching of the soil where silica and lime are leached away and a soil rich in oxides of aluminium predominate and are in abundance laterite is called baux- ite. Due to the presence of iron oxides the co- lour of laterite soil is basically red. This soil is poor in lime content and hence it is acidic. Laterite soils are found on the high level pla- teau and hilly areas that receive high rainfall and are specifically well developed on the Eastern Ghats in Orissa. It is also found in the southern part of the Western Ghats includ- ing the adjoining coastal regions in Ratnagiri District and Malabar.

Humus is almost absent in this type of soil. However, in the laterite soil developed in the forested areas in the western part of Karnata- ka, humus is present. Further, laterite soils of high level areas are very poor and least reten- tive of moisture and at times barren. But, in the low lying areas, regular addition of soils that are washed down from the adjacent high- er areas affects lateritization. In those areas, the lateritic soil being either loam or mud is useful and is regularly ploughed. For the con- tinuous cultivation of crops, regular applica- tion of fertilizers is required.

• Red Soil: Red soils are also known as yellow soils. Like laterite soil, red soils are heavily leached and they contain a considerable con- centration of iron oxides. The presence of iron oxides is responsible for giving this soil its reddish or yellowish shade. Red soils are sandier and less clayey comparatively. More- over, these soils are formed in those areas which receive relatively low rainfall and thus they are less leached as compared with later- ite soils. Further, red or yellow soils develop usually on metamorphic rocks.

Red soils does not contain any essential nu- trient. Like for instance, they are poor in ni- trogen, lime and phosphorous contents. Red soils are acidic in nature. This is one similar- ity between laterite soils and red soils. Red soils are not retentive of moisture and hence, they are cultivated mostly during the rainy season. For higher yield in this type of soil, constant application of manures is required. Red soils mostly develop in the Indian pen- insular plateau. Interestingly, in the lowlands and valleys, red soils are fertile and deep. On the other hand, on the hill slopes, they are ba- sically poor and thin.

The northwestern half of the peninsular block is covered by black soil and the remaining southeastern half is covered by red soil of various shades of red and yellow. They ba- sically surround the whole black soil region on all sides, and cover the eastern part of the peninsula, comprising Chhotanagpur Plateau, Orissa, eastern parts of Madhya Pradesh, Nil- giris and Tamil Nadu plateau. They continue

northwards in the west, along the Konkan coast of Maharashtra. They also develop in the Eastern Ghats, Bihar plateau, and Shill- ong plateau. It is found in states like Mizoram and Manipur. Soils are loamy in deep depres- sions and in uplands they consist of gravel. They function well with dosage of fertilizers and irrigation waters.

• Forest and Mountain Soil: Generally, there is a huge variety of soils in the Himalaya Mountain ranges. Mountain soils are found in the dry and cold districts like Ladakh, La- hul-Spiti, Kinnaur District, etc. Further, in the river valleys as well as on the river ter- races, alluvial soils are found but across the slopes, one generally comes across soils of different textures. It varies from silty loam to rock fragments. Fine textured soils are main- ly found in the river valleys or in the outwash plains. In other parts of these hilly districts, soils are in general stony and shallow but are poor in organic matter. The basic character of the mountain soils depend on the climate and are mainly found in the warm temperate belt or the cool temperate belt of the Hima- laya Mountains. Brown forest soil is mainly found in the warm temperate belt lying at heights ranging from 900 to 1800 metres, which has deciduous forests. This belt com- prises enough warmth for decomposition of vegetation. The typical brown forest soil of this zone is rich in humus and is deep. They are slightly acidic and are fertile largely used for raising different varieties of crops.
• Desert soils: A large part of the arid region belonging to the western Rajasthan, Haryana, Punjab, lying between the Indus River and the Aravalli range is affected by the desert condi- tions of geologically recent origin. This part is covered under a mantle of brown sand which, when combined with the arid climate results in poor soil development. The most predom- inant component of the desert sand is quartz but feldspar and hornblende grains also occur with a fair proportion of calcareous grains. It receives little monsoon rain. The sands which cover the area are partly derived from the disintegration of the subjacent rocks, but are

largely blown in from the coastal regions and the Indus Valley. Some of these soils contain high percentages of soluble salts, high pH, a varying percentage of calcium carbonate and are poor in organic matter. The Rajasthan desert is a vast sandy plain, including isolat- ed hills or out crops at places. Though on the whole the tract is sandy, the soil improves in fertility from west and north-west to east and northeast. In many parts, the soils are saline or alkaline, with unfavorable physical condi- tions and high pH.

• Peaty and marshy soil: Peaty soil originates in humid regions as a result of accumulation of large amount of organic matter in the soils. These soils contain considerable amount of soluble salts and 10-40 per cent of organ- ic matter. Soils belonging to this group are found in Kottayam and Alappuzha districts of Kerala where it is called KARI. Marshy soil with high proportion of vegetable matter also occurs in the coastal areas of Orissa and Tamil Nadu. The peaty soils are black, heavy and highly acidic. They are deficient in pot- ash and phosphate.
• Saline and alkaline soils: These soils are found in Andhra Pradesh and Karnataka. These soils are liable to saline and alkaline efflorescences and are known as reh, kallar, usar, rakar and chopan. These soils contain toxic concentrations of soluble salts in the root zone. Electrical conductivity in the sat- uration extract of such soils taken as a mea- sure of salts is greater than 4.0 mmhos/ cm. Exchangeable sodium percentage is less than 15 and pH is less than 8.5. The soluble salts mainly consist of chlorides and sulphates of sodium, calcium and magnesium. Because of the white encrustation due to salts, the soil is called white alkali. The soil salinity or al- kalinity or both have many adverse effects, summarized below:
  • Causing low yield of crops or crop fail- ure in extreme cases.
  • The limiting of the choice of crops be- cause some crops are sensitive to salinity or alkalinity or both.

• Rendering the quality of fodder as poor, as at times the fodder grown on alka- li soils may contain a high amount of molybdenum and a low amount of zinc, causing nutritional imbalance and disess- es among live-stock.
  • Creating difficulties in the construction of buildings and roads and their mainte- nance.
  • Causing excessive run offs and floods due to low infiltration resulting in dam- age to crops.

SOIL EROSION AND CONSERVATION #

Soil erosion in India is a major cause of concern. Almost 130 million hectares of land i.e. approx 45% of total land is affected by serious soil erosion through gorge and gully, shifting cultivation, water logging etc. Soil erosion is the gradual removal of the top soil cover by natural agencies like water, wind etc or by manmade activities as alkanisation, salinization of soil, deforestation etc.

Soil erosion is almost universally reorganized as a serious threat to man’s well-being. The two main agents of erosion are wind and water. In the case of erosion by water, the major erosive agents are impacting raindrops and run-off water flowing over the soil surface. Erosion and sedimentation embody the processes of detachment, transportation and deposition of soil particles. Detachments are the dislodging of soil particles from the soil mass by erosive agents.

Most of the land area in the country shows evi- dence of degradation thus affecting the productive base of economy. Out of the total geographical area of 329 million hectares, 175 million hectares are considered degraded.

Although soil-erosion is frequent throughout the country, it operates most intensely in the hilly regions. The precipitation often occurs in torrents which instead of sinking into the ground as the light drizzles, wash away the top layers of the soil. The steep slopes of the hills further stimulate the eroding power of the rain water. The soils are very thin and all exposed slopes are susceptible to serious sheet erosion or gullying.

Erosion may be of little consequence for hilly tracts, but is of great significance to the plains. The whole basin of Kosi river is threatened by this erosion, as a result of which the rivers bring with them millions of tonnes of sand and debris annually. When the rivers reach the plains and below and the stream flow slackens the load is dropped and gets deposited in their beds. This leads to choking of river channels, which in turn increase the flood dan- ger and induces shifting of the course which brings disaster in train to the whole country-side.

Both surface erosion and deep gullying are considerably influenced by the type of soil in India, although a given soil type may not behave consistently under all conditions and no type of soil is entirely safe from erosion. Thus, sandy porous soil in the country are in general least subject to gradual weathering down by water action, since they are capable of absorbing a great amount of water in ordinary rains. On the other hand, if the rate of percolation is prevented by frost or by even thin strata of clay, the very lack of “binding” qualities in the sandy soils permit them to be moved at a very rapid pace. Again, however, the coarseness of the material may cause it to be deposited before it has been carried to any great distance.

The most potent and common causes for erosion in India are deforestation and overgrazing. Through- out the country, as population has increased, more and more forests have been destroyed mainly by graz- ing cattle feeding on grass and herbs and green bushes.

Effects of soil erosion #

• Loss of fertile top soil leading to gradual loss of soil fertility and agricultural productivity.
• Loss of mineral nutrients from soil through

leaching and flooding.

• Lowering of the underground water table and decrease in the percentage of soil moisture.
• Drying of vegetation and extension of arid lands.
• Increase in frequency of droughts and floods.
• Silting of river and canal belts.
• Recurrence of landslides.
• Adverse effect on economic prosperity and cultural development.

Soil conservation #

Soil conservation is maintaining good soil health, by various practices. The aim of soil con- servation methods is to prevent soil erosion, prevent soil’s overuse and prevent soil contamination from chemicals. There are various measures that are used to maintain soil health, and prevent the above harms to soil. Here are the soil conservation methods which are practiced for soil management.

Strategies #

There are many ways to conserve soil, some are suited to those areas where farming is done, and some are ac- cording to soil needs. Here are the various soil conservation methods that are practiced.

• Planting Vegetation: This is one of the most effective and cost saving soil conservation methods. By plant- ing trees, grass, plants, soil erosion can be greatly prevented. Plants help to stabilize the properties of soil and trees also act as a wind barrier and prevent soil from being blown away. This is also among strategies used for soil conservation methods in ur- ban areas, one can plant trees and plants in the landscape areas of the residential places. The best choices for vegetation are herbs, small trees, plants with wild flowers, and creep- ers which provide a ground cover.
  • Contour Ploughing: Contour farm- ing or ploughing is used by farmers, wherein they plough across a slope and follow the elevation contour lines. This method prevents water runoff, and thus prevents soil ero- sion by allowing water to slowly penetrate the soil.
  • Maintaining the Soil pH: The mea- surement of soil’s acidity or alkalin- ity is done by measuring the soil pH levels. Soil gets polluted due to the

addition of basic or acidic pollutants which can be countered by main- taining the desirable pH of soil.

• Soil Organisms: Without the activ- ities performed by soil organisms, the organic material required by plants will litter and won’t be avail- able for plant growth. Using benefi- cial soil organisms like earthworms, helps in aeration of soil and makes the macro-nutrients available for the plants. Thus, the soil becomes more fertile and porous.
  • Crop Rotation Practice: Crop rotation is the soil conservation method where a series of different crops are planted one after the oth- er in the same soil area, and is used greatly in organic farming. This is done to prevent the accumulation of pathogens, which occur if the same plants are grown in the soil, and also depletion of nutrients.
  • Watering the Soil: We provide water to plants and trees, but it is equally important to water soil to maintain its health. Soil erosion occurs if the soil is blown away by wind. By watering and settling the soil, one can prevent soil erosion from the blowing away of soil by wind. One of the effective soil conservation methods in India is the drip irrigation system which provides water to the soil without the water running off.
  • Salinity Management: Excessive collection of salts in the soil has harmful effects on the metabolism of plants. Salinity can lead to death of the vegetation and thus cause soil erosion, which is why salinity management is important.
  • Terracing: Terracing is among one of the best soil conservation methods, where cul- tivation is done on a terrace leveled section of land. In terracing, farming is done on a unique step like structure and the possibility of water running off is slowed down.
  • Bordering from Indigenous Crops: It is preferable to plant native plants, but when native plants are not planted then bordering

the crops with indigenous crops is necessary. This helps to prevent soil erosion, and this measure is greatly opted in poor rural areas.

• No-tilling Farming Method: The process of soil being ploughed for farming is called tilling, wherein the fertilizers get mixed and the rows for plantation are created. However, this method leads to death of beneficial soil organisms, loss of organic matter and compac- tion of soil. Due to these side effects, the no-till- ing strategy is used to conserve soil health.
  • Increased use of organic manure: Through manuring, the Indian farmers can check the deflection of soil nutrients, which takes place with continuous cropping. Manures can be animal and plant residues. They ensure yet another aspect of soil conservation viz, the building up of soil productivity.
  • Keeping the soil covered: Grasses are even

more firm protectors of soil than the trees.

• River embankments: By making river em- bankments, soil erosion can be reduced along the bank of the rivers.

Vegetation #

Located at tropical latitudes, the beautiful land of India is characterized by rainfall regimes and diverse temperature and climate. India’s climate helps in the growth of forests in the country. However, in the past thousand years, various types of human activities have altered the climatic formations in the country to a large extent. The natural vegetation in India primarily comprise of forests.

Vegetation growing in correspondence with dif- ferent environmental conditions is the natural veg- etation of a particular place. Several major factors such as soil, topography, temperature and rainfall have influenced the natural vegetation of India to a large extent. Depending on the atmosphere, weather, position and other factors, there can be several classification of India’s natural vegetation. The features that characterize the natural vegetation of India are the tropical deciduous forests, the tropical rain forests, the alpine and tundra vegetation, rain forests of Southern India, Himalayan vegetation, the desert region, the temperature forests and grasslands and many more.

(A)   Moist Tropical Forests #

These forests are found in the areas of quite high temperature and rainfall. The forests are dense, multi-layered and have many types of trees, shrubs and lians. These forests are further categorized into 4 types depending on the degree of wetness in the area and the dominant life form in the forest.

1. Tropical moist evergreen forests: These are climatic climax forests found common- ly in areas having annual rainfall above 250 cm and temperature 25-30°C. These forests are chiefly distributed on the western face of Western Ghats, Assam, Cachar, parts of West Bengal, northern Canara, Annamalai Hills and Coorg in Meysore and Andman Islands.

The characteristic feature of these forests is dense growth of very tall trees having height of more than 45 m. Climbers, lians, epiphytes and shrubs are abundant but herbs and grass- es are rare in these forests. The carpet layer of herbs and grasses cannot grow because very dense layer of leaf canopy of trees does not allow enough light to reach to the ground.

Dominant trees in forests of west coast are Dipterocarpus indica, Palaquim and Cellen- ia while in forests of Assam are Diptercarpus macrocarpus, D. turbinatus, Shorea assamica, Mesua ferrea andKayea

• Tropical moist semi-evergreen forests: These are also climatic climax forests found commonly in areas of annual rainfall 200- 250 cm and temperature 25-32°C.These for- ests are chiefly distributed along the Western Ghats, in upper parts of Assam and Orissa and in Andman Islands. These forests are more developed in the northern India than in southern India.

Characteristic feature of these forests is dense growth of evergreen trees intermixed with de- ciduous trees that shed their leaves for very brief period of relative dryness. Average height of trees in these forests is 25-35 m and shrubs are common. Forests have rich carpet layer of herbs, grasses ferns and orchids.

Dominant trees in these forests are Diptero- carpus alatus, Hopea, Terminalia and Salma- lia in Andman Island; Artocarpus, Miche-

liaand Mangifera in Orissa; Schima wallichii, Bauhinia, Phobe and Ammora in Assam.

• Tropical moist deciduous forests: These forests are found in the area having tempera- ture of 25-30°C and quite high annual rainfall of 150-200 cm spread over most of the year but periods of rain alternating with very short periods of dryness. In several areas, the for- ests have been converted into open savannahs due to intensive biotic factors. These forests are chiefly distributed in a narrow belt along Himalayan foothills, on the eastern side of Western Ghats, Chota Nagpur, Khasi hills, in moist areas of Kerala, Karnataka, soth- ern Madhya Pradesh, parts of northern Uttar Pradesh, Bihar and West Bengal.

Chief characteristic of these forests is domi- nance of deciduous trees that remain leafless for one or two months only along with lower story of smaller trees and evergreen shrubs.

Dominant trees of these forests in north India are Tectona grandis, Shorea robusta, Salmella and Dalbegia while in south India are Tectona grandis and Shorea spp.

• Littoral and swamp forests: These forests are found in wet marshy areas, in river deltas, in saline or other swampy areas and along the sea coasts. They are chiefly distributed in del- tas of large rivers on the eastern coast and in pockets on the western coast (Tidal forests), in saline swamps of Sundarban in West Ben- gal, coastal areas of Andhra and Orissa (Man- grove forests) and in less saline or non-saline swampy pockets throughout the India.

Chief characteristic of these forests is domi- nance of halophytic evergreen plants of vary- ing height with varying density of plants in different area.

Dominant plants of tidal and mangrove for- ests are Rhizophora, Bruguiera, Ceriops, Horitora, Avicennia, Nipa, Sonneratia and Acanthus. In less saline swamps, dominant plants are Ipomea, Phoenix, Phragmitis, Ca- suarina, Manilkara and Calophyllum. In other swamps, the dominant plants areBarringto- nia, Syzygium, Myristica, Bischofia, Trowia, Lagerstroemia, Sophora, Pandanus, Entada and Premna.

(B)   Dry Tropical Forests #

These forests are found in the areas where wet season is followed by a relatively long period of dryness during which trees remain leafless. These forests are dominated by smaller trees and shrubs and have abundance of shrubs or sometimes grasses. This category includes three types of forests.

1. Tropical dry deciduous forests: These for- ests are found in areas having temperature of 25-32°C and annual rainfall of 75-125 cm along with a dry season of about six months. Distribution of these forests in northern India is in areas of Punjab, Haryana, Uttar Pradesh, Bihar and Orissa. In the southern and central India, these forests are distributed in dry areas of Maharashtra, Tamilnadu, Karnataka and Madhya Pradesh.

Chief characteristic feature of the forests is open canopy of small (10-15 m high) trees and abundance of shrubs.

Dominant species of the forests in north India are Shorea robusta, anogeissus, Terminalia, Buchnnania, Somocarpus, Carissa, Emblica, Madhuca, Acacia, Aegle, Diospyros, Bauhin- ia, Eugenia, Zyzyphus, Lannea, Sterculia, Dendrocalamus, Salmelia, Adina, Grewia, Adathoda and Helicteres. In south India, dominant plants are Tectona grandis, Dal- bergia, Kydia, Terminalia, Pterospermum, Dillenia, Acacia, Diospyros, Anogeissus, Bo- swellia, Bauhinia, Chloroxylon, Hardwickia, Soymida, Gymnosporia, Zyzyphus, Dendro- calamus and Holorrhena.

• Tropical thorn forests: These forests are found in the areas of high temperature of 27-30°C and very low annual rainfall of 20- 60 cm with long periods of dryness. These forests are distributed in western Rajasthan, parts of Maharashtra, Madhya Pradesh and Tamilnadu.

Chief charateristic of such forests is sparse distribution of small (8-10 m high) mostly thorny trees with shrubs being more common than trees. The plants in these forests remain leafless for most of the year. They develop leaves only during the brief rainy season when grasses and herbs also become abundant.

Dominant plants in these forests are Acacia nilotica, A. leucophloea, A. senegal, Prosopis spicigera, P. juliflora, Albizzia and Capparis.

• Tropical dry evergreen forests: These for- ests are found in the areas of relatively high temperature and small rainfall available only during summers. The forests are distributed in some parts of Tamilnadu and Karnataka.

Chief characteristic features of the forests are dense distribution of mixed small evergreen and deciduous trees of 10-15 m height, ab- sence of bamboos and abundance of grasses.

Dominant plants in the forests are Memecy- lon, Maba, Pavetta, Foronia, Terminalia, Ixo- ra, Sterculia, Mesua and Schleichora.

(C)   Montane Subtropical Forests #

These forests occur in the areas where climate is cooler than tropical but warmer than temperate areas

i.e. on the hills between the altitudes of 1000 m and 2000 m. The forests are dominated by semi-xero- phytic evergreen plants. This category includes three types of forests.

1. Sub-tropical broad-leaved hill forests: These forests occur in relatively moist areas at lower altitudes on mountain ranges. Their chief distribution is in eastern Himalayas of West Bengal and Assam, hills of Khasi, Nilg- iri and Mahabaleshwar.

Chief characteristic feature of the forests is dense growth of evergreen browd-leaved trees with abundant growth of climbers and epiphytic ferns and orchids.

Dominant trees in the forests of north are Quercus, Schima and Castanopsis with some temperate species.

In the southern areas, dominants are Eugenia and members of family Lauraceae.

• Sub-tropical dry evergreen forests: These forests occur in areas having quite low tem- perature and rainfall. The forests are distrib- uted in the lower altitudes of eastern and western Himalayas.

Chief characteristic feature of the forests is presence of thorny xerophytes and small leaved evergreen plants.

Dominant plants in the forests are Acacia modesta, Dodonea viscosa and Olea cuspidata.

• Sub-tropical pine forests: These forests oc- cur at middle altitudes between 1500- 2000 m in Himalayas. They are distributed in western Himalayas from Kashmir to Uttar Pradesh. In eastern Himalayas, the forests occur in Khasi Jayantia Hills of Assam.

Chief characteristics of the forests are open formations of pine trees.

Dominant trees in the forests are P. roxburghii and Pinus khasiana.

(D)   Temperate Forests #

These forests are found in the areas having quite low temperature along with comparatively high humidity than the comparable areas of higher lati- tudes. The cause of high humidity is greater rainfall in Himalayas except in parts of Uttar Pradesh, Pun- jab, Himachal Pradesh and Kashmir where humidity is lower. The forests occur mainly in the Himalayas at altitudes 2000-4000 m. The forests are generally dominated by tall conifers or angiospermic evergreen trees with abundance of epiphytic mosses, lichens and ferns. The category includes three types of forests.

1. Wet temperate forests: These forests are found at altitudes of 1800-3000 m in the cool- er and humid mountains. They are distributed in the eastern Himalayas from eastern Nepal to Assam, in the western Himalayas from Kashmir to western Nepal and in Nilgiri Hills of south Indian.

Chief characteristic feature of the forests in the Himalayas is dense formation of ever- green, semievergreen broad-leaved and co- niferous trees of up to 25 m height. In south India, these forests are termed Shola forests and mostly have 15-20 m high broad-leaved trees with dense leaf canopy, abundant epi- phytic flora and rich herbaceous undergrowth.

Dominant trees in the forests of western Hi- malayas are angiosperms like Quercus, Bet- ula, Acer, Ulmus, Populus, Corylus, Caprinus etc. and conifers like Abies, Picea, Cedrus etc.

• Himalayan moist temperate forests: These forests are found at 1700-3500 m altitude in eastern and western Himalayas. These occur

in areas having annual rainfall above 100 cm but relatively less than that in areas of wet temperate forests.

Chief characteristic feature of the forests is presence of tall (up to 45 m high) conifers, oaks or their mixture along with thin partly deciduous undergrowth.

Dominant trees in the eastern Himalayas are Tsuga dumosa, Quercus lineata, Picea spinu- losa, Abies densa and Quercus pachyphylla. In the western Himalayas, dominants in low- er zones are Quercus incana, dialata, Cedrus deodara, Pinus wallichiana, Picea smithiana, Abies pindrew, Cotoneaster, Berberis and Spire while in the higher zones the dominants are Quercus semicarpifolia and Abies pindrew.

• Himalayan dry temperate forests: These forests occur in the regions of Himalayas having very low rainfall. They are distributed in both eastern and western Himalayas.

Chief characteristic feature of the forests is dominance of evergreen oaks and conifers. Undergrowth is formed by scrubs.

Dominant trees in the forests of comparative- ly drier western Himalayas are Pinus gerard- iana and Quercus ilex. In the comparatively wetter western Himalayan region, the dom- inants are Abies, Picea, Larix griffithia and Juniperus wallichiana.

(E)   Alpine Forests #

These forests are found in the regions of Himalayas having extremely low temperature and humidity. The forests are dominated by perennial and annual herbs and grasses though some trees may also be present in areas of relatively high humidity. Abundant lichen flora is characteristic feature of these forests. This category includes three types of forests.

1. Sub-alpine forests: These forests are found in open strands throughout the Himalayas be- tween the altitude 3500 m and the tree tine.

Chief characteristic feature of the forests is presence of some evergreen conifers and broad-leaved trees along with prominent shrub layer.

Dominant trees in the forests are Abies spec- tabilis, Rhododendron and Betula. Prominent

shrubs in the forests are Cotoneaster, Rosa, Smilax, Lonicera and Strobilanthus.

• Moist alpine scrub forests: These forests are found in the Himalayas above the tree line up to 5500 m altitude in somewhat moist areas.

Chief characteristic feature of the forests is dominance of dwarf, evergreen shrubby coni- fers and broad-leaved trees along with prom- inent shrub layer under them.

Dominant trees in the forests are Juniperus and Rhododendron

• Dry alpine forests: These forests are found in comparatively more dry areas of Himala- ya’s upto 5500 m altitude.

Chief characteristic feature of the forests is open formation of xerophytic scrubs with many herbs and grasses.

Dominant plants in the forests are Juniperus, Caragana, Eurctia, Salix and Myricaria.

Biosphere Reserves #

• A Biosphere Reserve is a unique and repre- sentative ecosystem of terrestrial and coastal areas which are internationally recognised within the framework of UNESCO Man and Biosphere (MAB) Programme.
  • There are 14 Biosphere Reserves in India . Four Biosphere Reserves, namely (i) Nilgiri;

(ii) Nanda Devi (iii) Sunderbans; and (iv) Gulf of Mannar have been recognised by the UNE- SCO on World Network of Biosphere Reserves.

Nanda Devi Biosphere Reserve #

• The Nanda Devi Biosphere Reserve situated in Uttaranchal includes parts of Chamoli, Almora, Pithoragarh and Bageshwar districts.
  • The major forest types of the reserve are tem- perate. A few important species are silver weed and orchids like latifolie and rhododendron.
  • The biosphere reserve has a rich fauna, for example the snow leopard, black bear, brown bear, musk deer, snow- cock, golden eagle and black eagle.
  • Major threats to the ecosystem are the collec- tion of endangered plants for medicinal use, forest fires and poaching.

Sunderbans Biosphere Reserve #

• It is located in the swampy delta of the river Ganga in West Bengal.
  • It extends over a vast area of 9,630 sq. km and consists of mangrove forests, swamps and forested islands.
  • Sunderbans is the home of nearly 200 Royal Bengal tigers.

In the Sunderbans, the mangrove forests are characterised by Heritiera fomes, a species valued for its timber.

Nilgiri Biosphere Reserve #

• The first of the fourteen biosphere reserves of India, was established in September 1986.
  • It embraces the sanctuary complex of Wyanad, Nagarhole, Bandipur and Mudumalai, the entire forested hill slopes of Nilambur, the Upper Nilgiri plateau, Silent Valley and the Siruvani hills. The total area of the biosphere reserve is around 5,520 sq. km.
  • The Nilgiri Biosphere Reserve possesses dif- ferent habitat types, unspoilt areas of natural vegetation types with several dry scrubs, dry and moist deciduous, semi- evergreen and wet evergreen forests, evergreen sholas, grasslands and swamps.
  • It includes the largest known population of two endangered animal species, namely the Nilgiri Tahr and the Lion-tailed macaque.
  • Good number of endemic and endangered plants are also found in this reserve.

Gulf of Mannar Biosphere Reserve #

• The Gulf of Mannar Biosphere Reserve cov- ers an area of 105,000 hectares on the south- east coast of India. The biosphere reserve comprises 21 islands with estuaries, beaches, forests of the nearshore environment, sea grasses, coral reefs, salt marshes and man- groves. Among the Gulf’’s 3,600 plant and animal species are the globally endangered

e.g. sea cow (Dugong dugon). Besides six mangrove species, endemic to Peninsular India are also endangered.