Forestry & Forest Sciences · Forest Ecology & Biology · also Forest Types of India, Forest Geography, Vegetation of the World
How forests are classified and mapped: world biomes and forest formations, and national forest-type classifications such as Champion and Seth's for South Asia.
In the exams: ICAR AICE-JRF 59 Unit 1 (forest types, world forest types, phytogeographical regions); ICAR AIEEA-PG Group 09 (types, classification); IFoS Forestry Paper I Section A (temperate, tropical, mangrove and cold-desert silviculture)
Forests differ enormously across the world, from the dark spruce taiga of Siberia to the multi-layered rain forests of Borneo, from the deciduous teak forests of central India to the mangroves of the Sundarbans. Forest types and biogeography is the subject that describes these differences, explains them in terms of climate, soil, history and disturbance, and organises them into classifications that foresters, ecologists and planners can use. A forest type is a unit of forest that is recognisable by its composition, structure and site, and that can be mapped and managed as a whole.
The subject has three parts. The first is global: the world's forest biomes and the floristic regions of the world and of South Asia. The second is classification: the principles of physiognomic, floristic and ecological classification, and in particular the revised classification of the forest types of India by H. G. Champion and S. K. Seth, which remains the standard framework for working plans and examinations in South Asia. The third is mapping and conservation: how forest cover is mapped and reported nationally, as in the Forest Survey of India's State of Forest Report, and how biodiversity hotspots and endemism guide conservation priorities. The ecological processes that shape forests, such as succession, productivity and disturbance, are covered in forest ecology; the silviculture of individual species and forest types is covered in silviculture of species and silvicultural systems.
The subject is examined in ICAR's AICE-JRF forestry paper (forest types, world forest types and phytogeographical regions), in ICAR's AIEEA-PG (types and classification), and in the UPSC Indian Forest Service Forestry optional, which asks about the silviculture of tropical, temperate, mangrove and cold-desert forests. State forest service papers ask for Champion and Seth type groups, characteristic species and distribution. Figures such as areas and percentages change with each assessment and differ between sources; the manual gives them as approximate and names the source.
A biome is a major regional ecosystem characterised by its dominant vegetation life form and climate, such as tropical rain forest, savanna or boreal forest. Whittaker's biome diagram places the world's biomes on axes of mean annual temperature and mean annual precipitation, showing forests where precipitation is sufficient for trees, savannas and shrublands where it is lower or more seasonal, and deserts where it is lowest. The Holdridge life zone system classifies vegetation by biotemperature, annual precipitation and the ratio of potential evapotranspiration to precipitation; Köppen's climate classification is also widely used to relate climate to vegetation. Fire, soils and herbivores modify the climatic pattern, so forest, savanna and grassland can occur under the same climate.
According to FAO's Global Forest Resources Assessment 2020, forests cover about 4.06 billion hectares, roughly 31 per cent of the world's land area. FAO defines forest as land of more than 0.5 hectare with trees taller than 5 metres and canopy cover of more than 10 per cent, or trees able to reach these thresholds, not predominantly under agricultural or urban use. By climatic domain, the tropical domain holds the largest share of the world's forest area, followed by the boreal, temperate and subtropical domains.
The boreal forest, or taiga, forms a broad belt across northern North America, Scandinavia and Russia, between the tundra and the temperate zone. Winters are long and cold, the growing season short, and soils often acidic, nutrient-poor and underlain by permafrost in the north. The forests are dominated by a few conifer genera, spruce (Picea), fir (Abies), pine (Pinus) and larch (Larix), with broadleaves such as birch, aspen and poplar. Larch, a deciduous conifer, dominates large areas of eastern Siberia where permafrost and extreme cold prevail. Fire and insects are the main natural disturbances. Boreal forests store much of their carbon in soils and peat.
Temperate forests occur in the mid-latitudes. Temperate deciduous broadleaved forests, dominated by oaks, beeches, maples, ashes, limes and chestnuts, cover much of eastern North America, Europe and East Asia, where rainfall is spread through the year and winters are cold enough for trees to shed leaves. Temperate coniferous forests occur in mountains and in regions with dry summers or poor soils. Temperate rain forests, among the tallest and most biomass-rich forests on earth, occur in very wet, mild oceanic climates, as on the Pacific coast of North America (Douglas-fir, Sitka spruce, western hemlock, western red cedar, coast redwood), southern Chile, Tasmania and New Zealand.
Mediterranean-type climates have mild, wet winters and hot, dry summers. They occur in five regions of the world: the Mediterranean Basin, California, central Chile, the Cape region of South Africa, and south-western and southern Australia. Their vegetation is dominated by sclerophyllous (hard-leaved) evergreen trees and shrubs adapted to summer drought and frequent fire, such as holm oak, cork oak and stone pine around the Mediterranean, and forms shrublands with regional names: maquis and garrigue in the Mediterranean, chaparral in California, matorral in Chile, fynbos in the Cape and kwongan in Australia. Despite their small total area, these regions are exceptionally rich in plant species and endemism.
Tropical moist forests, including tropical rain forests, occur near the equator where temperatures are high all year and rainfall is abundant with no long dry season. The largest blocks are the Amazon basin, the Congo basin and the forests of South-East Asia, including the dipterocarp forests of the Malay archipelago. They have the highest productivity, biomass and tree species diversity of all forests, with complex vertical structure, buttressed trees, lianas and epiphytes. Most nutrients are held in the biomass, and soils are often old and poor.
Tropical dry forests occur where a long dry season of several months alternates with a wet season, as in monsoon regions of South Asia, parts of Africa, Central America and northern Australia. Many trees shed their leaves in the dry season. These forests, including the teak and sal forests of India, have been more heavily cleared and degraded than moist forests because their climate and soils suit agriculture and settlement. With decreasing rainfall and increasing fire and grazing, tropical dry forests grade into savanna woodlands, thorn forests and scrub.
Savannas are tropical and subtropical ecosystems with a continuous grass layer and scattered trees, covering large parts of Africa, South America, Australia and South Asia. They occur under climates that could support forest in some places and not in others, and the boundary between forest and savanna is maintained by a combination of rainfall seasonality, soil, fire and herbivory. Frequent grass fires kill tree seedlings and saplings and keep the canopy open; where fire is excluded, many savannas in wetter regions gradually turn into forest. This has led ecologists to regard forest and savanna as alternative stable states under the same climate, a view that matters for afforestation programmes: planting trees in ancient, species-rich savannas and grasslands can destroy valuable ecosystems rather than restore forest, so the original vegetation of a site must be understood before planting.
Phytogeography, or plant geography, studies the distribution of plants and the reasons for it. Floristic classifications divide the world into regions with distinctive floras, defined by the presence of endemic families, genera and species rather than by vegetation structure. The widely used scheme developed by Ronald Good and refined by Armen Takhtajan recognises six floristic kingdoms: the Holarctic (most of the northern hemisphere outside the tropics), the Palaeotropical (tropical Africa, Asia and the Pacific), the Neotropical (tropical America), the Cape (the south-western tip of Africa), the Australian, and the Holantarctic or Antarctic (southern South America, New Zealand's subantarctic islands and Antarctica). The Cape kingdom is by far the smallest yet has an extraordinarily rich and endemic flora. Kingdoms are divided into regions and provinces.
Historical factors, especially continental drift and past climate change, explain many distributions. Plants of Gondwanan origin, such as southern beeches (Nothofagus) and Podocarpus, occur on now-separated southern continents. Biogeographic boundaries, such as Wallace's line between the faunas and floras of Asia and Australia, mark long separations.
India lies at the meeting point of the Indo-Malayan, Palaearctic and Afrotropical influences, which gives it a mixed and rich flora. Early botanists divided India into botanical or phytogeographical regions; D. Chatterjee's 1939 scheme is the classic one, recognising regions such as the Eastern Himalaya, Western Himalaya, Indus plain, Gangetic plain, Central India, Deccan, Malabar, Assam and the Andaman Islands.
For conservation planning, the Wildlife Institute of India's biogeographic classification by Rodgers and Panwar (1988), revised by Rodgers, Panwar and Mathur (2002), divides India into ten biogeographic zones: the Trans-Himalaya, Himalaya, Indian Desert, Semi-Arid, Western Ghats, Deccan Peninsula, Gangetic Plain, North-East, Coasts and Islands, each subdivided into provinces. This zonation was used to assess the coverage of India's protected area network. Each zone has characteristic forest types: the Western Ghats and North-East contain most of the tropical evergreen forests, the Deccan Peninsula is dominated by dry and moist deciduous forests, the Trans-Himalaya by cold desert vegetation, and the Coasts and Islands by mangrove, littoral and island forests.
The same broad patterns continue across South Asia. Nepal and Bhutan span tropical sal forests in the Terai and lower hills through subtropical chir pine and broadleaved forests, temperate oak, fir and hemlock forests, to subalpine birch and rhododendron and alpine scrub, compressed into a short horizontal distance by steep elevation gradients. Bangladesh has tropical semi-evergreen hill forests in the Chittagong Hill Tracts, moist deciduous sal forests in the centre and north, and the Bangladesh part of the Sundarbans mangroves. Sri Lanka has wet evergreen forests in the south-west, which share many species with the Western Ghats, dry monsoon forests in the north and east, and montane cloud forests. Pakistan's forests range from coastal mangroves of the Indus delta and riverine forests to subtropical scrub, chir pine and temperate conifer forests of the north-west Himalaya and Hindu Kush.
In mountains, temperature falls with elevation, roughly by about 6 °C for every 1,000 metres in many regions, so vegetation belts succeed each other with height in a pattern that resembles the change with latitude. The Himalaya show this especially clearly: from tropical and subtropical forests in the foothills and valleys, through subtropical pine and broadleaved forests, temperate broadleaved and conifer forests, subalpine fir and birch, to alpine scrub and meadows and finally rock and snow. The elevations of the belts differ between the wetter eastern and drier western Himalaya, between outer and inner ranges, and between north- and south-facing slopes; south-facing slopes are warmer and drier, so belts lie higher on them. Understanding zonation helps foresters predict which species will succeed at a planting site and how belts may shift with climate warming.
Classification groups forests into units that are similar enough to be described, mapped, managed and compared. Different purposes need different classifications: a global vegetation map needs broad structural units; a working plan needs units that predict growth and silvicultural response; a conservation plan needs units that capture biodiversity. Most practical systems combine several criteria.
Physiognomic classification uses the structure and appearance of vegetation: the dominant life form (trees, shrubs, herbs), height, density of the canopy, leaf type (needle-leaved or broadleaved) and leaf habit (evergreen or deciduous). Examples are the global formation classes of tropical evergreen forest, deciduous forest, woodland and savanna, and the UNESCO international classification of vegetation (1973), which arranges formations hierarchically by these features. Physiognomic units can be recognised from a distance and from remote sensing without species identification, which makes them useful for broad mapping, but they can group floristically very different forests.
Floristic classification uses species composition. The Braun-Blanquet or Zürich-Montpellier school of phytosociology defines plant associations by characteristic and differential species, recorded in relevés (sample plots) and organised in tables; associations are grouped into alliances, orders and classes. Simpler floristic units are named by their dominant species, such as sal forest, teak forest or oak-rhododendron forest. Floristic units capture biodiversity and site conditions well but require botanical expertise and may change with disturbance.
Ecological classification uses site factors, such as climate, landform, soil and moisture, alone or together with vegetation. Habitat type classification, developed by R. Daubenmire in the north-western United States, classifies sites by their potential climax vegetation, so that a disturbed site can still be assigned to its habitat type. Ecological land classifications in Canada, Europe and elsewhere stratify landscapes into regions, districts and site types by climate, geology, soil and vegetation together. Ecoregions, such as those mapped by the World Wildlife Fund, combine biogeographic history with ecological conditions.
Champion and Seth's classification of Indian forests, described in the next chapter, is a combined system: its major groups are climatic, its type groups are largely physiognomic, its types are defined floristically, and it adds edaphic, seral and degradation categories that capture site and disturbance.
H. G. Champion published a preliminary survey of the forest types of India and Burma in 1936. With S. K. Seth he revised it as A Revised Survey of the Forest Types of India, published in 1968, which remains the standard reference. The classification is hierarchical. At the top are major climatic groups (tropical, subtropical, temperate, subalpine and alpine), divided into 16 type groups, which are further divided into subgroups and some two hundred individual forest types. Types are named and coded: the type group number, a letter for the subgroup, and a type number, with additional symbols for edaphic types (E), seral types (S) and degradation stages (DS). For example, a code beginning with 3C indicates a subgroup of the tropical moist deciduous type group.
The type groups are: 1 tropical wet evergreen; 2 tropical semi-evergreen; 3 tropical moist deciduous; 4 littoral and swamp; 5 tropical dry deciduous; 6 tropical thorn; 7 tropical dry evergreen; 8 subtropical broadleaved hill; 9 subtropical pine; 10 subtropical dry evergreen; 11 montane wet temperate; 12 Himalayan moist temperate; 13 Himalayan dry temperate; 14 sub-alpine; 15 moist alpine scrub; 16 dry alpine scrub. Groups 1 to 7 are tropical, 8 to 10 subtropical, 11 to 13 temperate and 14 to 16 subalpine and alpine.
Champion and Seth based their primary units on climatic climax vegetation, recognising that a forest's potential composition is set by climate, especially rainfall amount and seasonality and temperature, which change with latitude and elevation. Within each climatic type they recognised edaphic types determined by soil and water (such as riverine, swamp and laterite forests), seral types representing stages of succession (such as early riverain khair-sissoo forests on new alluvium), and degradation stages produced by fire, grazing, lopping and cutting (such as scrub and grassland derived from forest). This made the classification useful for management, because a forester could recognise both the potential of a site and its current state.
The tropical type groups cover most of India's forest area, with the tropical dry deciduous and tropical moist deciduous groups together accounting for the largest share, followed by the thorn, semi-evergreen and wet evergreen groups; temperate, subalpine and alpine types are confined to the Himalaya and a few southern mountains. The Forest Survey of India has mapped forest types across the country using the Champion and Seth framework and published atlases of forest types, with area estimates that should be taken from the latest report. The classification is used in working plans to describe each compartment, in examinations, and in ecological research. It has limitations: some types are defined from limited data, boundaries between types are gradual, and much forest has been altered since the 1960s, so that the mapped type may describe the potential rather than the present vegetation.
Champion and Seth described forest types as related to the climate of the early and mid-twentieth century. As climate warms and rainfall patterns change, the potential vegetation of many sites will change too: treelines may rise, drought-sensitive moist types may contract towards wetter areas, and fire regimes may intensify in dry forests. Modelling studies for India have projected shifts in the boundaries of forest types under future climate scenarios, with large uncertainties. In practice this means that type maps should be updated, that species chosen for planting should suit the likely future climate as well as the present one, and that connectivity between forest patches along elevation and moisture gradients becomes more important, so that species can move. Monitoring of permanent plots across type boundaries provides the evidence needed to detect such shifts.
Tropical wet evergreen forests develop where annual rainfall is high, commonly above about 2,500 millimetres, and the dry season is short. In India they occur in the Western Ghats, the North-East and the Andaman and Nicobar Islands. They are tall, dense, multi-storeyed forests with a closed evergreen canopy often 40 metres or more high, many tree species, abundant climbers and epiphytes, and buttressed trunks. Characteristic genera include Dipterocarpus, Hopea, Mesua, Calophyllum, Artocarpus, Myristica and, in the North-East, Dipterocarpus and Shorea species. Regeneration is mostly of shade-tolerant species in gaps, and management has been mainly protective, with selection-cum-improvement fellings in the past.
Tropical semi-evergreen forests are transitional between wet evergreen and moist deciduous forests, occurring where rainfall is somewhat lower or the dry season longer. They contain a mixture of evergreen species and deciduous species such as Terminalia, Lagerstroemia and Tetrameles, and are found along the Western Ghats, in the North-East, Odisha and the Andamans.
Tropical moist deciduous forests occur where annual rainfall is roughly 1,500 to 2,000 millimetres or so, with a distinct dry season during which the dominant trees shed their leaves. They are among the most important timber forests of India. Sal (Shorea robusta) forms extensive moist deciduous forests in the north and north-east, the Terai and Bhabar of the sub-Himalayan tract, and parts of central and eastern India; teak (Tectona grandis) forms moist teak forests in the Western Ghats and central India. Associated species include Terminalia, Dalbergia latifolia, Pterocarpus marsupium, Lagerstroemia, Adina and bamboos. Fire, grazing and past over-cutting have degraded much of this type.
Rainfall figures used to separate tropical types are approximate: the boundaries depend also on the length of the dry season, temperature, soil water and fire, and different authors give different ranges.
Tropical dry deciduous forests occur where rainfall is lower, roughly 1,000 millimetres or a little more down to about 750 millimetres, with a long dry season. They form the most extensive forest type group in India, covering much of the Deccan plateau, central India, the drier parts of the Gangetic plain and the lower Western Ghats. The canopy is lower and more open than in moist forests, and trees are leafless for a long period. Characteristic species include dry teak, Anogeissus latifolia, Terminalia tomentosa, Boswellia serrata, Hardwickia binata, Diospyros melanoxylon (tendu), Buchanania lanzan, dry sal in some regions, and bamboos such as Dendrocalamus strictus. Many species coppice well, and these forests have long supplied fuelwood, poles, fodder and non-timber products under coppice and coppice-with-standards systems.
Tropical dry evergreen forests are a distinctive small type on the Coromandel coast of Tamil Nadu and Andhra Pradesh, where much of the rain falls from the north-east monsoon; they consist of low, dense evergreen trees and shrubs such as Manilkara hexandra and Memecylon, and survive mostly as small remnants, often in sacred groves.
Sal and teak, the two most important timber species of Indian tropical forests, form distinct types across a range of rainfall. Sal is gregarious, forming nearly pure stands over large areas; it occurs in moist deciduous forests of the sub-Himalayan tract, the North-East and eastern India, and in dry deciduous forests of central India and the eastern plateau, where it is shorter and more open. It prefers deep, well-drained soils and avoids waterlogging and heavy clays. Teak occurs naturally in peninsular India (and in Myanmar, Thailand and Laos), not in the Himalaya or the North-East, in moist and dry deciduous forests, usually mixed with other species rather than in pure stands, and is planted far beyond its natural range. In central India the two species occupy largely different areas, sal mainly to the east and teak mainly to the west and south, with a zone where both occur. Both species show many forms of degradation, from fully stocked high forest to coppice scrub, which Champion and Seth recognised as degradation stages within the types.
Between the tropical and temperate belts lie the subtropical forests of the lower Himalaya and the North-East, roughly between about 1,000 and 2,000 metres, though limits vary with latitude and aspect. Subtropical pine forests are dominated by chir pine (Pinus roxburghii) in the western and central Himalaya, a fire-adapted, light-demanding species tapped for resin, and by Khasi pine (Pinus kesiya) in the Khasi hills and North-East. Subtropical broadleaved hill forests, found in the North-East, the Nilgiris and other hills, contain oaks, chestnuts (Castanopsis), Schima and laurels. Subtropical dry evergreen forests in the drier north-western Siwaliks and outer hills consist of low scrubby forest with wild olive (Olea ferruginea) and Acacia modesta.
Himalayan moist temperate forests occur roughly between 1,500 and 3,300 metres in the outer and middle Himalaya where monsoon rainfall is substantial. In the western Himalaya they include oak forests dominated by ban oak (Quercus leucotrichophora) at lower levels, moru oak (Q. floribunda) higher up and kharsu oak (Q. semecarpifolia) near the upper limit, together with conifer forests of deodar (Cedrus deodara), blue pine (Pinus wallichiana), silver fir (Abies pindrow) and spruce (Picea smithiana). The eastern Himalaya has wetter temperate forests rich in oaks, magnolias, rhododendrons, hemlock (Tsuga) and fir. Montane wet temperate forests also occur in the southern hills, notably the shola forests of the Nilgiris, Anamalais and Palnis, stunted evergreen forests in sheltered valleys forming mosaics with grasslands.
Himalayan dry temperate forests occur in the inner valleys behind the main ranges, in the rain shadow where monsoon rainfall is low and much precipitation falls as winter snow, as in parts of Kinnaur, Lahaul, Chamba and Kashmir. They are open forests of chilgoza pine (Pinus gerardiana), deodar, blue pine and junipers, with dry shrubs.
Subalpine forests form the upper belt of tree growth, roughly from about 3,000 to 3,800 metres or higher, up to the treeline. They are dominated by fir (Abies spectabilis), birch (Betula utilis, whose bark was used for writing manuscripts) and rhododendrons such as Rhododendron campanulatum, with junipers in drier areas. Above the treeline lie moist alpine scrub of dwarf rhododendrons and junipers with alpine meadows in the wetter Himalaya, and dry alpine scrub of junipers, Caragana and other spiny shrubs in the dry inner and trans-Himalayan regions. The treeline is set mainly by low growing-season temperature, and is expected to shift upwards with climate warming, though grazing, fire and local conditions also matter.
Temperate and alpine forests protect the headwaters of major rivers, stabilise steep slopes and support pastoral communities. Their management in India is dominated by protection, regeneration and control of grazing and fire, with commercial felling largely stopped in many Himalayan states, as noted in silvicultural systems.
Mangroves are forests of salt-tolerant trees and shrubs growing in the intertidal zone of sheltered tropical and subtropical coasts, estuaries and deltas. They are adapted to saline, waterlogged, anaerobic, unstable mud by special roots, salt regulation and reproduction. Pneumatophores, vertical breathing roots rising from the mud, are typical of Avicennia and Sonneratia; stilt or prop roots arching from the trunk support Rhizophora; knee roots occur in Bruguiera; buttresses and plank roots occur in others. Some species, such as Rhizophora, exclude salt at the roots, while others, such as Avicennia, excrete salt through leaf glands. Many mangroves are viviparous: the seed germinates while the fruit is on the tree, and the propagule falls and floats until it lodges in mud.
The Sundarbans of India and Bangladesh, in the delta of the Ganga, Brahmaputra and Meghna, is the largest single mangrove forest in the world and a World Heritage site; it is named after sundari (Heritiera fomes) and is home to the tiger. Other major Indian mangroves include Bhitarkanika in Odisha, the Godavari and Krishna deltas, Pichavaram in Tamil Nadu, the Gulf of Kachchh and the Andaman and Nicobar Islands. India's mangrove cover, as reported by the Forest Survey of India, is of the order of 5,000 square kilometres; the latest State of Forest Report should be consulted for current figures. Mangroves protect coasts from storms and erosion, support fisheries and store large amounts of carbon in their soils, but have been widely cleared for aquaculture, agriculture and settlement.
Littoral forests grow on sandy beaches and dunes just above the tidal zone, on well-drained but nutrient-poor, salt-sprayed soils. Typical species include Calophyllum inophyllum, Thespesia populnea, Pongamia pinnata, Pandanus, Barringtonia and, in the Andamans and elsewhere, Casuarina equisetifolia, which is also planted widely for shelterbelts and fuelwood along the Indian coast. Ground cover includes creeping plants such as Ipomoea pes-caprae and Spinifex that bind sand. Coastal shelterbelts reduce wind and salt spray inland, and plantations after the 2004 tsunami and cyclones have been promoted for coastal protection, though their effectiveness depends on width, structure and site.
Swamp forests occur on waterlogged freshwater sites. Myristica swamps, dominated by species of Myristicaceae with stilt and knee roots, are rare relict freshwater swamp forests in the Western Ghats of Kerala, Karnataka and Goa. Other swamp forests occur in the North-East and in the Terai. In Champion and Seth's classification, mangrove, beach and freshwater swamp forests are included in type group 4, littoral and swamp forests.
Mangrove management emphasises protection, restoration and sustainable use. Restoration succeeds best when hydrology, the natural flow of tides and fresh water, is restored first and species are planted at the right elevation in the tidal frame; planting mangroves on mudflats or seagrass beds where they did not grow often fails. Harvest-based management, such as the clear-felling system with small coupes in the Matang mangroves of Malaysia (see silvicultural systems), shows that sustained yield is possible where tidal conditions are maintained. Community involvement, regulation of aquaculture and protection of the landward margin for future inland migration with sea-level rise are central to modern mangrove conservation.
Within a mangrove forest, species are often arranged in zones parallel to the shore, related to how often and how long each zone is flooded by tides, to salinity and to soil. In many Indo-Pacific mangroves, Avicennia and Sonneratia colonise the seaward and pioneer zones on soft mud, Rhizophora occupies frequently flooded middle zones, Bruguiera and Ceriops lie further inland, and Heritiera, Excoecaria and others grow on the landward margin where flooding is less frequent and fresh water more available. Zonation differs from place to place and is not always distinct, and the causes include tidal elevation, salinity, propagule dispersal, predation of propagules by crabs, and competition. Recognising the natural zonation of a site is the basis for choosing species when restoring mangroves.
Tropical thorn forests develop where annual rainfall is low, roughly below 750 millimetres, with a long, hot dry season, in north-western India (Rajasthan, Gujarat, Punjab and Haryana), and in the rain shadow of the Western Ghats in the Deccan. They are open, low forests and scrub of spiny, small-leaved, often deciduous trees and shrubs: Acacia species (including Acacia nilotica and A. senegal), Prosopis cineraria (khejri), Capparis decidua, Ziziphus, Salvadora and Balanites, with drought-resistant grasses. Heavy grazing, fuelwood collection and the introduced Prosopis juliflora, now invasive across large areas, have greatly changed them.
The Thar desert of Rajasthan and adjoining Pakistan has very low and erratic rainfall, high temperatures and sandy soils. Its vegetation includes trees such as khejri, which is valued for fodder, fuel and soil improvement and is central to traditional agroforestry and to the culture of the Bishnoi community, rohida (Tecomella undulata), ber (Ziziphus) and Salvadora; shrubs such as Calligonum polygonoides and Leptadenia pyrotechnica that bind sand; and grasses such as sewan (Lasiurus sindicus). Afforestation in the desert relies on drought-hardy species, water harvesting, sand-dune stabilisation with shelterbelts and microcatchments, and protection from grazing.
The cold deserts of India lie in the trans-Himalaya: Ladakh, Lahaul and Spiti, and parts of Kinnaur and northern Sikkim, in the rain shadow of the Great Himalaya. Precipitation is very low and falls mostly as snow; winters are extremely cold, the growing season is short, solar radiation is intense and soils are thin and poor. Natural vegetation is sparse dry alpine scrub and steppe: junipers, Caragana, Artemisia, Ephedra, Myricaria and sea buckthorn (Hippophae), with willows and poplars along streams. Willows and poplars are traditionally planted along irrigation channels for fuel, fodder and timber. Sea buckthorn is valued for its berries, soil binding and nitrogen fixation through Frankia.
Silviculture in cold deserts depends on irrigation water from snow-fed streams, protection from grazing, the use of hardy species and planting stock suited to the short season, and careful timing of planting in spring or early summer. Survival is often limited by drought, frost heaving and browsing.
Dry-zone forestry shares principles across hot and cold deserts: choose drought-hardy, preferably local species; harvest water with trenches, half-moons and microcatchments; plant larger pits with good soil working; protect plantations from grazing; and use shelterbelts to reduce wind erosion. The techniques are described in forest nursery and plantation establishment and restoration of difficult sites. Because dryland vegetation recovers slowly, its conservation and the rights of pastoralists who depend on it are as important as planting.
Two quite different measures of forest are reported in many countries. Recorded forest area, or forest land, is land legally designated as forest in government records, such as reserved, protected and unclassed forests in India, whether or not it actually carries trees. Forest cover is land actually carrying tree canopy above a defined density, as seen on satellite images, whatever its legal status or ownership. The two overlap but differ: some recorded forest is degraded and treeless, and some tree-covered land, such as orchards, plantations on private land and village woodlots, lies outside recorded forest. Clear definitions are essential when comparing figures.
The Forest Survey of India publishes the India State of Forest Report (ISFR) every two years. It maps forest cover from satellite imagery, at present medium-resolution data of the Indian Remote Sensing satellites, interpreted at a scale of 1:50,000 with a minimum mappable unit of one hectare. Forest cover is defined as all lands more than one hectare in area with a tree canopy density of more than 10 per cent, irrespective of ownership, legal status and land use. Forest cover is divided into three density classes: very dense forest, with canopy density of 70 per cent and above; moderately dense forest, 40 to 70 per cent; and open forest, 10 to 40 per cent. Scrub is degraded land with canopy density below 10 per cent. Tree cover, the patches of trees outside recorded forest smaller than one hectare, is estimated separately by sampling, and forest cover plus tree cover is reported as total forest and tree cover.
Recent reports have placed India's forest cover at around 21 to 22 per cent of the country's geographical area, and total forest and tree cover at around a quarter of it; the exact figures change with each report and with improvements in methods. The reports also give state-wise figures, mangrove and bamboo cover, carbon stocks, forest fire data and growing stock from the national forest inventory.
Satellite-based forest cover mapping has known limitations. The 10 per cent canopy threshold counts plantations, orchards and tree crops as forest cover, so an increase in cover can hide the loss of natural forest. Medium-resolution imagery may miss small clearings and degradation within a canopy, and changes in data and methods between reports can create apparent changes. Critics have therefore argued for reporting natural forest, plantations and tree crops separately and for using higher-resolution imagery. Users should read the methods section and compare like with like.
Other countries publish similar national reports, and the FAO Global Forest Resources Assessment compiles national data every five years using FAO definitions. Independent global maps, such as annual tree-cover loss maps produced from Landsat imagery by university and NGO partners, give consistent global comparisons but use different definitions (tree cover rather than forest land use), so their figures do not match national reports directly.
Besides mapping forest cover, the Forest Survey of India carries out a national forest inventory of growing stock on a systematic grid of sample plots, inventories trees outside forests, estimates bamboo resources, assesses forest carbon stocks for national reporting, and runs a forest fire alert system based on satellite detection of active fires. These datasets complement cover maps: cover shows where tree canopy exists, while inventory shows what the forests contain and how much wood and carbon they hold. Inventory design and estimation are covered in forest inventory and sampling. State forest departments add their own working plan data, which are more detailed but are not collected in a uniform way across states.
A species is endemic to an area if it occurs naturally there and nowhere else. Endemism can be measured at any scale, from a single mountain to a continent. Areas of high endemism are irreplaceable for conservation because their species cannot be protected elsewhere. Palaeoendemics are old lineages that were once widespread and now survive in restricted areas, often as relicts; neoendemics are recently evolved species that have not yet spread. Islands, isolated mountains and old, stable landscapes tend to have high endemism. In India, the Western Ghats, the Eastern Himalaya, the North-East and the Andaman and Nicobar Islands are centres of plant endemism; the Western Ghats are especially rich in endemic amphibians, freshwater fish and flowering plants.
The biodiversity hotspot concept was introduced by Norman Myers in 1988 to identify regions where conservation investment would protect the most species per unit effort. In the widely used definition by Myers and colleagues (2000), adopted by Conservation International, a hotspot must contain at least 1,500 species of endemic vascular plants (more than 0.5 per cent of the world's total) and must have lost at least 70 per cent of its original natural vegetation. The original analysis identified 25 hotspots; later additions have brought the number to 36. Together they cover only a small fraction of the earth's land surface but hold a large share of its endemic plant and vertebrate species.
Four hotspots include parts of India: the Himalaya; Indo-Burma, which includes the North-East outside the Himalaya; the Western Ghats and Sri Lanka; and Sundaland, which includes the Nicobar Islands. India is also one of the world's megadiverse countries, a group of seventeen countries identified as holding the majority of the world's species.
Hotspots are one of several global prioritisation schemes. Others include high-biodiversity wilderness areas, which are species-rich but still largely intact; WWF's Global 200 ecoregions; Important Plant Areas; Key Biodiversity Areas; and endemic bird areas. Each uses different criteria and answers a different question. The hotspot approach has been criticised for focusing on plants and vertebrates, for using a large scale that hides variation within hotspots, and for directing attention away from intact areas. Within a hotspot, conservation planning still needs finer-scale data on species distributions, threats and protected-area coverage.
For foresters, hotspots and endemism mean that forest management in such regions must give special weight to protecting remaining natural forest, avoiding conversion to plantations, maintaining connectivity between fragments, and conserving rare and endemic species, often with the involvement of local communities and traditional protection such as sacred groves, discussed in forest ecology.
A student should be able to list Champion and Seth's sixteen type groups in order with their climatic group, name characteristic species and distribution for each, explain the difference between physiognomic, floristic and ecological classification, describe the world's forest biomes and their climates, recognise mangrove root types and species, give the ISFR definitions and density classes, and name India's biogeographic zones and hotspots. Field visits should include recognising forest types on the ground and relating them to rainfall, elevation and soil.
A forester five years into service describes each compartment's forest type in working plans using Champion and Seth codes, recognises degradation stages and edaphic or seral types and prescribes treatment accordingly, uses ISFR maps and state data to plan protection and afforestation, and manages special types such as mangroves, sholas, Myristica swamps and cold-desert plantations with the care they need.
A senior forester with twenty-five years' experience uses type and cover data at state or national level: setting priorities for conservation of rare types and hotspots, guiding afforestation to suit the potential type of each site, interpreting changes in forest cover reports for policy and explaining their limitations, and contributing to national reports to FAO and international conventions.
A researcher with long field experience studies the distribution and dynamics of forest types: updating classifications with new plot data and remote sensing, mapping shifts of treelines and types under climate change, analysing biogeographic history and endemism with molecular data, and improving the methods of national forest cover mapping. Such work informs revisions of type classifications and conservation planning.
This manual gives the type groups and representative species of Champion and Seth's classification but does not list all of its individual types and codes, which should be taken from the original work and the Forest Survey of India's forest type atlas. Areas, percentages and mangrove figures change with each State of Forest Report and FAO assessment and are given only approximately. Rainfall and elevation limits for types are approximate and vary between authors. Floristic regions within kingdoms, the forest types of other South Asian countries in detail, and the silviculture of individual species are not covered here; the latter belongs to silviculture-of-species.
Original practice questions written to the syllabus and pattern of the exams named in each question's examTags. They are not past papers and do not reproduce any board's questions.
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