Plant geography and vegetation zones of the Himalaya



The Moon and Thamserku (6608 m), Dudh Kosi Valley, eastern Nepal. In the upper alpine zone, very few plants grow, mostly lichens. The altitudinal record among seed plants is held by a species of sandwort, Arenaria bryophylla, which was found on Mt. Everest in 1921, at an altitude of 6,180 m. (Photo copyright © by Kaj Halberg)




During the Tertiary Period, c. 65 million years ago, a vast ocean, the Tethys Sea, stretched across what is today the northern part of the Indian Subcontinent, separating the huge Asiatic continent to the north from a smaller continent to the south – what is today India.

About 5 million years later, continental drift caused the smaller continent to be pushed beneath the larger continent. The Tethys Sea shrunk, as the continuous continental drift was pressing huge land masses upwards. This was the beginning of the process, which created the highest mountain range in the world: the Himalaya.

Most authorities consider Nanga Parbat, a mountain in northern Pakistan, as the westernmost peak in the Himalaya. Many others, however, also include the Karakoram Mountains further north, although, strictly speaking, they are not part of the Himalaya proper. The easternmost part of the range is c. 2,600 km to the south-east, in the northern tip of Myanmar.

In Sanskrit, himalaya means ’the abode of snow’ – a suitable name, as the 14 peaks on Earth, which exceed 8,000 m altitude, are found in this mountain range, including Sagarmatha (8850 m), in the West known as Mt. Everest, in Tibet as Chomolangma, K 2 (8611 m), in the West also called Godwin Austen, in Sinkiang Dapsang, Kangchendzonga (8586 m), Lhotse (8511 m), Makalu (8463 m), Cho Oyu (8201 m), Dhaulagiri (8167 m), Manaslu (8163 m), Nanga Parbat (8125 m), Annapurna I (8091 m), and Shishapangma (8013 m), also called Gosainthan.

The mountain folding is an ongoing process, and, parallel to the Himalaya proper, lower mountain ranges have been formed. The middle range, in Nepal called Mahabharat, reaches an altitude of c. 3,000 m, whereas the southern range, in India called Siwalik, and in Nepal Churia, reaches c. 1,800 m. The flat lowland at the foot of the mountains, which in many places is less than 100 m above sea level, is called Terai.

The rivers of the Asiatic Continent, which were originally running north-south into the Tethys Sea, managed to cut channels through the newly created land at about the same pace, as the land was rising.

Traditionally, the Kali Gandaki Valley, situated in central Nepal between the peaks of Annapurna I (8091 m) and Dhaulagiri (8167 m), is regarded as the deepest canyon in the world – although it is not nearly as dramatic as the Grand Canyon in the United States, or the Fish River Canyon in Namibia.

When these mountains were formed, many lakes were created, the major part of which have long since been drained by continuing erosion. One example is the Kathmandu Valley, which, until c. 40,000 years ago, was a huge lake. The majority of today’s lakes are reservoirs, and most of the natural lakes are rather small, some examples being Dal Lake in Kashmir, Hem Kund in Uttarakhand, and Lake Rara in western Nepal. As opposed to the Himalaya proper, the Tibetan Plateau has an abundance of natural lakes, big and small, most of which are more or less salty.



View of the Kali Gandaki Valley, looking south from the small town of Kagbeni. (Photo copyright © by Kaj Halberg)




Factors affecting plant life
The Himalaya is the meeting-point of two bio-geographical regions. In most areas of the mountain range, flora and fauna from the Indo-Malayan Region are dominant, but in Kashmir, Ladakh, and northern Pakistan, and elsewhere at altitudes above c. 3,500 m, there is a large element of species from the West and North Asian Palaearctic Region.

The Himalaya is home to an overwhelming abundance of plant species. In Nepal alone, c. 6,500 species of seed plants have been found, and the number in the entire mountain range exceeds 10,000. To this number, hundreds of species of ferns, clubmosses, mosses, and lichens must be added.

In his book Forests of Nepal, Stainton describes 35 different plant communities, which can be grouped into six altitudinal zones. As local conditions of the terrain have a huge influence on the micro-climate of a specific area, these zones often overlap several hundred metres in altitude. The most important factors, which affect distribution of plant species, are altitude, precipitation, latitude, sun exposure, soil composition, and, to a great extent, human influence on Nature.

Most of the plant species mentioned below are dealt with in detail on the pages Plants: Himalayan flora 1, 2, and 3.




The tropical zone
Tropical conditions prevail from the Terai, up to an altitude of c. 700 m (excepting Pakistan and Kashmir, both of which are too far north for tropical conditions). In the Terai, the forest is dominated by a dipterocarp, named sal (Shorea robusta), and many other species, including khair acacia (Senegalia catechu), silk-cotton tree (Bombax ceiba), Indian rosewood (Dalbergia sissoo), and Mallotus philippinensis, of the spurge family (Euphorbiaceae). Formerly, vast areas of the Terai were covered in swamps and grassland, containing more than one hundred grass species.

Until around 1950, a deadly form of malaria was raging in the Terai and the lower foothills, causing this area to be sparsely populated. Since then, draining and spraying with pesticides have largely eliminated the disease, and the major part of the area has been converted into farmland. Today, the indigenous flora and fauna of this zone is almost exclusively restricted to nature reserves.



Heavily grazed forest of sal (Shorea robusta) in the Terai, the tropical lowland of southern Nepal. With the exception of nature reserves, the indigenous flora and fauna of this zone is found in ever decreasing areas of forest, in which huge herds of cattle are ravaging. (Photo copyright © by Kaj Halberg)



Early in spring, the flowering sal trees of the Terai are a spectacle to behold. (Photo copyright © by Kaj Halberg)




The subtropical zone
In the eastern part of the Himalaya, the subtropical zone is found up to c. 1,800 m altitude, whereas in the western part, in northern Pakistan, it reaches about 1,400 m. Numerous forest types are found in this zone, including dry deciduous, wet deciduous, dry evergreen, and wet evergreen, and in the easternmost part of the mountains subtropical rainforest. Several of these forest types are again divided into sub-groups, often named after the dominant tree species.

In the western part of the Himalaya, from the Indian State of Himachal Pradesh eastwards to central Nepal, the dominant tree species in the lower foothills is sal (see above), which, above c. 1,000 m, is replaced by the chir, or long-leaved, pine (Pinus roxburghii). Other characteristic species of this zone include a species of olive, Olea cuspidata, a camel’s-foot tree, Bauhinia variegata, a coral tree, Erythrina stricta, and Butea monosperma, the latter two belonging to the pea family (Fabaceae).

The eastern part of the mountains is far more humid than the western part. Dominant species include Schima wallichii of the tea family, two chestnut species, Castanopsis indica and C. tribuloides, both with edible fruits, Terminalia crenulata of the leadwood family, Lagerstroemia speciosa of the loosestrife family, a screw palm, Pandanus nepalensis, a date palm, Phoenix humilis, a cycad, Cycas pectinata, and tree ferns, such as Cyathea spinulosa.

Following the intensive malaria control, the major part of the foothills are today inhabited, and most of the forest has been cleared and converted into farmland. The remaining forest is widely utilized for timber, firewood, fodder, and grazing. In many places, plantations of important timber species, such as sal, chir pine, and Schima wallichii, have been established.



Buddhist shrines, called chortens, are Tibetan style stupas. Religious relics, e.g. bones or hairs from a holy man, are often buried beneath such shrines. These chortens are covered in fallen needles of chir pine (Pinus roxburghii). (Photo copyright © by Kaj Halberg)




Lower temperate zone
This zone is situated in the middle mountain range, the Mahabharat, between 1,400 and 2,700 m altitude. Although this region is densely populated and extensively cultivated, some forest has been preserved, often dominated by species of oak (Quercus), which the local people make use of for countless purposes: timber, foliage for fodder, acorns for food and medicine, bark for tanning etc. Nepalese alder (Alnus nepalensis), which is a true pioneer species, often forms light forests along rivers and in landslides.

In the wetter part of the mountains, from central Nepal eastwards, the most common species in this zone are an oak, Quercus lamellosa (by some known as Cyclobalanopsis lamellosa), and blue pine (Pinus wallichiana). Other species include Lithocarpus pachyphylla of the beech family, the tall Rhododendron arboreum, a maple, Acer campbellii, ten species of magnolia, of which M. campbellii is the most common, three species of Deutzia, of the hydrangea family, several species of Prunus, and many others. The trees are often densely draped with epiphytes, especially lichens, ferns, mosses, begonias, and orchids of the genera Coelogyne and Dendrobium.

Further west, the climate is much drier, the vegetation being dominated by three oak species, Quercus semecarpifolia, Q. floribunda, and Q. incana, and others, including blue pine, Himalayan spruce (Picea smithiana), Himalayan cedar, or deodar (Cedrus deodara), Indian horse-chestnut (Aesculus indicus), common walnut (Juglans regia), maple species, and members of the laurel family, such as Machilus odoratissima. Today, this forest type is highly threatened, covering only about 55,000 km2.

The understorey and clearings are often covered in shrubs, including two beautiful members of the heath family, Pieris formosa and Gaultheria fragrantissima, various species of St. John’s wort (Hypericum), indigo plants, Indigofera, and brambles, Rubus, the latter genus comprising no less than c. 45 species.



Nordindien 1997
Following a rain shower, a double rainbow stands like an arch over an oak forest in the Indian State of Uttarakhand. (Photo copyright © by Kaj Halberg)



Magnolia campbellii, displaying gorgeous white flowers in April-May, is quite common in the lower temperate zone in eastern Himalaya. (Photo copyright © by Kaj Halberg)



No less than c. 45 bramble species (Rubus) are found in the Himalaya. Among these, Rubus ellipticus, which is very common in open, slightly eroded areas at lower altitudes, produces the most delicious fruits, here shown by my guide, Dil Bahadur Pantha. (Photo copyright © by Kaj Halberg)




Upper temperate zone
Vast areas of this zone, between c. 2,400 and 3,500 m, are covered in mixed forests of various trees, including oak species, blue pine, two species of yew (Taxus), Himalayan spruce, Himalayan hemlock (Tsuga dumosa), and especially Himalayan silver fir (Abies spectabilis), which is a very important timber tree. In the westernmost part of the mountains, West Himalayan silver fir (Abies pindrow) and chilgoza pine (Pinus gerardiana) are also important trees.

Rhododendron species, notably R. arboreum and R. barbatum, also form forests. During their flowering period, in March-April, large tracts of forest have a reddish or pinkish tinge from millions of rhododendron flowers. Incidentally, the former species is the national plant of Nepal, called lali guras.

In this zone, the forest floor is often covered in dense shrubs of various species of dwarf bamboo, especially of the genera Arundinaria and Thamnocalamus. Conspicuous shrubs include species of Viburnum and barberry (Berberis), and a beautiful, yellow-flowered bush of the pea family, Pipthanthus nipalenses. Due to their bizarre appearance, Arisaema species, of the arum family, stand out among the herbs. No less than c. 16 species of these remarkable plants can be encountered. Clusters of epiphytic orchids are often found on trunks of older trees, chiefly four species of Pleione.



Monsoon clouds envelop upper temperate forest at an altitude of c. 3,500 m, near Gopte, Langtang National Park, central Nepal. (Photo copyright © by Kaj Halberg)



Magnificent old moss-clad trunks of Himalayan hemlock (Tsuga dumosa) on a mountain ridge named Propang Danda, near Gosainkund, central Nepal. (Photo copyright © by Kaj Halberg)



Various species of dwarf bamboo often form dense shrubs on the forest floor in the upper temperate zone. (Photo copyright © by Kaj Halberg)




Subalpine zone
This zone is found at various altitudes, mostly between 3,000 and 4,200 m. The forests here are dominated by Himalayan birch (Betula utilis) and Himalayan silver fir, in places mixed with Himalayan spruce, species of whitebeam (Sorbus), East Himalayan larch (Larix griffithiana), and the rare Nepalese larch (L. himalaica), which is restricted to a small area on the border between Nepal and Tibet. The forest floor is often covered in dense shrubs of dwarf bamboo.

In drier areas, three species of juniper, Juniperus indica, J. recurva, and J. semiglobosa, form open forests. Shrubs like barberry, honeysuckle (Lonicera), and the fragrant Daphne bholua var. glacialis, grow here and there. Herbs include species of larkspur (Delphinium), primrose (Primula), saxifrage (Saxifraga), Bergenia, and various composites, including the beautiful genera Cremanthodium and Ligularia.



Forest of Himalayan birch (Betula utilis) at an altitude of c. 3,000 m, eastern Nepal, prior to foliation. In the centre, a single Rhododendron campylocarpum is glowing intensely, displaying hundreds of yellow flowers. (Photo copyright © by Kaj Halberg)



Nepal 2013
East Himalayan larch (Larix griffithiana) is common in the subalpine zone, from eastern Nepal eastwards. (Photo copyright © by Kaj Halberg)




Alpine zone
The alpine zone is above the tree limit, from c. 3,700 to 4,000 m, bordering areas of eternal snow and ice. Here you find dwarf shrubs like two junipers, Juniperus recurva and J. squamata, besides species of honeysuckle, barberry, and rhododendron, members of the pea family, and Gerard’s joint-pine (Ephedra gerardiana).

During the rainy season, between June and September, the alpine meadows display a wonderful selection of herbs, comprising species of primrose, cinquefoil (Potentilla), poppy (Meconopsis), larkspur, saxifrage, roseroot (Rhodiola), umbellifers, members of the pea family, composites like Aster, edelweiss (Leontopodium), and Saussurea and many others. Various members of the gentian family can be seen as late as November.

In snow-free areas above c. 5,500 m, the majority of plants are lichens. A few seed plants, however, are also able to survive the harsh conditions. The altitudinal record is held by a species of sandwort, Arenaria bryophylla, which was found on Mt. Everest in 1921, at an altitude of 6,180 m.



Above the tree limit is the alpine zone, which houses many dwarf shrubs, such as Rhododendron setosum, shown here. (Photo copyright © by Kaj Halberg)




The major part of the Himalaya receives most precipitation during the monsoon, from late May to late September. The monsoon is a humid wind, travelling over the Indian Subcontinent from the Bay of Bengal, as well as from the Arabian Sea. Part of the rain fall takes place on the plains of India, but the majority falls on the southern slopes of the Himalaya.

In the eastern part of the mountains, the monsoon begins in late May, in Nepal in mid-June, and in the far west, in northern Pakistan, not until early July. In the eastern part, the monsoon ends late September, whereas in Pakistan it ends as early as the beginning of this month. In the western part, however, quite a lot of precipitation falls in the winter, whereas rain at this time of the year is sparse in the eastern mountains.

In Darjiling, West Bengal, the mean annual rainfall is 3,100 mm, of which only 518 mm falls outside the monsoon season. For comparison, Srinagar, in Kashmir, experiences a mean annual precipitation of 661 mm, of which only 195 mm falls during the monsoon.

As a result of the abundant rainfall in the eastern Himalaya, the flora of this region is extremely varied and lush. As you move west, the number of species diminishes gradually. In the westernmost parts of the mountains, you encounter a number of genera, which are mainly found in Iran and around the Mediterranean, i.e. areas with dry summers. These western species include a lily, Eremurus himalaicus, a tulip, Tulipa stellata, and two species of eryngo, Eryngium billardieri and E. biebersteinianum.

When the monsoon has passed over the highest parts of the Himalaya, almost all rain has fallen, and the Tibetan Plateau north of the mountains receives very little precipitation. This plateau, the major part of which is situated at altitudes between 3,500 and 4,500 m, is criss-crossed by mountain ranges. Politically, most of this habitat is a part of China, although a small part of it is found in Pakistan, India, Nepal, and Bhutan.

Plants in this area are adapted to the dry climate. Shrubs grow here and there, among others comprising species of juniper and honeysuckle, the pretty Rosa webbiana, and prickly members of the pea family, such as Caragana and Astragalus. Lush vegetation of willow (Salix), a species of false tamarisk (Myricaria squamosa), and Tibetan sea-buckthorn (Hippophae tibetana), is only encountered along streams. Herbs are numerous, comprising species of cranesbill (Geranium), primrose, lousewort (Pedicularis), columbine (Aquilegia), Corydalis, and others.



Plant hunting during the monsoon can be a very wet experience. These women in the Marsyangdi Valley, central Nepal, seek shelter from heavy rain beneath plastic sheets. Before the introduction of plastic items in the Himalaya, banana leaves, or other large leaves, would serve the same purpose. (Photo copyright © by Kaj Halberg)



A caravan of horses on its way up the Konze La Pass (4905 m), Ladakh. On the Tibetan Plateau, rivers form green, meandering lines across the barren landscape. (Photo copyright © by Kaj Halberg)




It is a widespread misconception that the Himalaya runs west-east – in fact the course of the mountain chain is northwest-southeast. The difference in latitude between northernmost Pakistan and the southernmost spurs of the Himalaya, in eastern Nepal, is almost ten degrees – similar to the distance between Hamburg and Rome. For this reason, the climate in north-western Himalaya is more temperate than further southeast.

As a rule, the tree limit, as well as the snow limit, of the western area is 300 to 400 m lower than further east. Snowfall is common in Srinagar, Kashmir, whereas it never snows in Kathmandu, which is situated at the same altitude, but 6.5 degrees latitude further south. Not surprisingly, far more species of North Asian and European origin are found in the northwestern region than in the southeastern.



Himalayan birch (Betula utilis), its branches draped with old man’s beard lichens (Usnea), Nanda Devi National Park, Uttarakhand. In the background Changabang (6864 m), a white granite peak. (Photo copyright © by Kaj Halberg)




Sun exposure
In steep mountains like the Himalaya, slopes facing north receive much less sunlight than south-facing slopes, the latter having a tendency to dry out in the intense sunshine, whereas north-facing slopes retain much moisture. Therefore, as a rule, north-facing slopes have far more plant species than south-facing ones. While a north-facing slope is usually clad in dense forest, often only tough grasses and a few other drought-resistant plants, such as woody, cactus-like species of spurge (Euphorbia), are able to grow on a south-facing slope.



This cactus-like candelabra spurge, Euphorbia royleana, grows on a dry slope near Uttarkashi, Uttarakhand. (Photo copyright © by Kaj Halberg)




Soil composition
It may come as a surprise that many plant species in the Himalaya do not have a special preference, regarding soil composition. Chir pine, for instance, grows on acid as well as calcareous soil, which is also the case for many species of rhododendron, which, among gardeners, are normally considered to prefer acid soil. This said, many species do prefer to grow on either acid or calcareous soil. One example is the Himalayan cypress (Cupressus torulosa), which is only found on calcareous soil.



Himalayan cypress prefers to grow on calcareous soil. This picture is from the Upper Kali Gandaki Valley, Annapurna, Nepal. (Photo copyright © by Kaj Halberg)




Human influence
Below c. 2,500 m altitude, the Himalaya is densely populated, and the human influence on nature is tremendous. Large tracts of forest have been cleared for farmland, and many trees are felled for timber or firewood. Many plantations have been established, but not sufficient to fulfill the demand.

Most of the remaining natural forest is utilized for extensive grazing, and the foliage is lopped of various tree species, also for fodder. Numerous grazing grounds have been established in the upper valleys, utilized between June and September, and the surrounding forests bear the imprint of extensive usage for firewood and timber for temporary huts. Grazing eliminates many plant species, whereas others, especially toxic or spiny ones, benefit from it, including Iris kemaonensis, Anemone rivularis, Astragalus candolleanus, primrose species (Primula), and poppies of the genus Meconopsis.

Many areas are regularly burned to promote growth of grasses for fodder. These fires often spread to the surrounding forest, and certain tree species, such as silver fir, hemlock and cypress, are much harmed by them. Large individuals of chir pine can survive a fire, while young trees are killed. The opposite effect is seen on blue pine. Fires kill older trees, but promote germination of the seeds. In areas with regular fires, large tracts are covered in young forest of blue pine, often with dwarf bamboo beneath. Agriculture benefits numerous weeds, of which many are also found in Europe and North America.

In the major part of the Himalaya, areas with natural vegetation cover steadily decreases, and today, most of the indigenous forest is found in the eastern part of the mountains, especially in Bhutan and the Indian State of Arunachal Pradesh, the former having a forest cover of no less than 70%. Percentage of forest cover decreases gradually, as you go west. Between 1990 and 1995, the forest area in Nepal decreased by one fourth (11,000 km2), and in 1995 the forest cover had reached a low of c. 25%. In Pakistan, the situation is critical. In the Karakoram Mountains, less than 20,000 km2 of forest is left, and this area is diminished year by year.

For thousands of years, local inhabitants of the Himalaya have been utilizing plants for traditional medicine, and collecting these plants is still a very common practice. Several species are seriously threatened by over-collecting, including Sinopodophyllum hexandrum of the barberry family, a species of sagebrush, Artemisia brevifolia, and a composite, Saussurea costus. Some species diminished by 80% in just ten years. An Indian NGO, the Pragya Project, is trying to protect these species through cultivation of seriously threatened species, education of locals, and establishing local groups to promote a sustainable usage of the plants.

Since the 1970s, the magnificent landscapes of the Himalaya have been a much coveted goal for trekkers. Within a few years, numerous tourist groups began camping in the mountains, and local villagers established small hotels, where individual trekkers could eat and sleep.

Especially during the 1980s and 1990s, these thousands of tourists had a significant effect on the vegetation. On average, c. 10 kilos of firewood was used per trekker per day. Naturally, this wood was collected in the surrounding forest, and along the most popular trekking destinations, forests soon bore the stamp of overuse.

In the 1990s, new restrictions were introduced to reduce the effect on the forest. Camping groups must now bring stoves and kerosine for cooking, and individual trekkers are instructed to frequent hotels, which utilize solar energy or hydro-electricity for cooking and for heating water for showers.



In the Himalaya, huge tracts of forest have been cleared to make room for the growing population. This picture shows terraced fields in Garhwal, Uttarakhand. (Photo copyright © by Kaj Halberg)



This forest on a mountain slope near Hellok, Tamur Valley, eastern Nepal, has recently been felled and burned, and now a woman is sowing maize in the ashes. Despite being extremely destructive to the fragile ecology of the mountains, slash-and-burn cultivation is still widespread in the Himalaya. (Photo copyright © by Kaj Halberg)



Iris kemaonensis, which grows between 2,800 and 4,200 m altitude, is the commonest among 11 iris species in the Himalaya. Irises are poisonous, and grazing animals avoid them, for which reason they often grow on pastures. (Photo copyright © by Kaj Halberg)




Paradise for botanists
Despite the massive influence on the vegetationen of the Himalaya, by locals as well as tourists, these mountains are no less than a paradise for botanists. Only a few other places on the Planet, one is able to experience so many climatic zones – and, with that, a tremendous variety of plants – within a limited area.

To experience the magnificent flora of the Himalaya, it is often necessary to get away from densely populated areas. As a large part of the mountains are without roads, you must often walk rather long distances to reach the botanically interesting areas. However, a dense network of trails is criss-crossing the mountains, as the locals, for thousands of years, have been transporting goods on the back of porters, horses, mules, or yaks.

In popular tourist destinations, such as Kathmandu and Pokhara in Nepal, Manali in Himachal Pradesh, Leh in Ladakh, and Darjiling in West Bengal, it is possible to hire porters or horsemen to transport tents, cooking equipment, food etc. to areas without hotel facilities.



The Himalaya is no less than a paradise for botanists. In this picture, my guide Ganga Thapa is standing among lush vegetation at an altitude of c. 3,000 m in the Rolwaling Valley, eastern Nepal, comprising a yellow species of poppy, Meconopsis paniculata, a whitish umbellifer, Pleurospermum benthamii, and a red lousewort, Pedicularis megalantha, besides numerous ferns. (Photo copyright © by Kaj Halberg)



Plant hunting in upper alpine valleys can be a harsh experience. In this picture, we are camping among spiny shrubs of barberry (Berberis) and junipers (Juniperus) at an altitude of c. 4,000 m in the Upper Ghunsa Valley, eastern Nepal, not far from the third-highest mountain in the world, Kangchendzonga (8586 m). (Photo copyright © by Kaj Halberg)




References (Nos. 115, 166, 301, 401, 403, 501, 502, 701) (Nos. 514, 1020, 1021)
Berthelsen, A. 1998. Rejsen til den blå sø. Gads Forlag. (In Danish)
Polunin, O. & A. Stainton 1984. Flowers of the Himalaya. Oxford University Press
Stainton, J.D.A. 1972. Forests of Nepal. John Murray, London




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