Altitudinal zonation of Himalayan vegetation

Topic: Natural Vegetation and Forests of India · NCERT: Class 11, Ch 5 "Natural Vegetation"

Meaning

Altitudinal zonation of Himalayan vegetation is the way plant life on the Himalayas is arranged in belts by height. Deciduous forest grows in the foothills. Above it come oak–chestnut, chir pine, deodar, blue pine–spruce and alpine trees and pastures. Above about 4,000 m, only mosses and lichens grow.

It matters because one Himalayan slope shows every vegetation type, from tropical to tundra (cold, treeless land). This explains where timber, resin, handicraft woods and summer pastures come from. It also explains problems such as spring forest fires in Uttarakhand.

Explanation

Why vegetation changes with height

Temperature falls with altitude (height above sea level).
As you climb, the air gets cooler.
Cooler air changes how much heat and moisture plants get.
So different plants grow at different heights, in belts stacked one above the other.
Climbing is like moving towards the poles.
Going up a high mountain is like travelling from the equator towards the poles.
So tropical, temperate and tundra plants can all appear on one slope.
The Himalayas have room for every belt.
They lie at about 27°–36°N.
They rise from low foothills to peaks over 8,000 m.
So they hold every belt from tropical forest to tundra.

The belts, from lowest to highest

Altitude	Climate type	Vegetation	Use / note
Foothills	Tropical	Deciduous forest (trees that shed leaves in the dry season)	Shiwalik and Terai margins
1,000–2,000 m	Wet temperate	Evergreen broadleaf oak and chestnut	Oak holds water and feeds hill springs
1,500–1,750 m	Warm temperate	Chir pine	Main commercial tree: timber and resin
Higher temperate zone	Temperate	Deodar, chinar, walnut	Deodar for building; chinar and walnut for Kashmir handicrafts
2,225–3,048 m	Cool temperate	Blue pine, spruce; temperate grasslands	Mixed conifer belt
3,000–4,000 m	Alpine	Silver fir, juniper, pine, birch, rhododendron; alpine pastures	Near and above the tree line
Above ~4,000 m	Tundra	Mosses and lichens	Below the snowline

Chir pine is a conifer (a tree that bears cones and has needle leaves). It gives:
timber, for buildings and furniture
resin, a sticky sap used to make turpentine and rosin
Deodar (Himalayan cedar, Cedrus deodara) is a true cedar of the genus Cedrus, and pure stands grow at about 1,900–2,700 m [2].
Its wood is strong and lasting, and it resists rot.
It is used for buildings, bridges and railway sleepers.
Alpine trees near the tree line grow short and twisted. The reasons are cold, wind and a short growing season.

Overlaps, the tree line and tundra

Belts can overlap.
The wet temperate belt (1,000–2,000 m) and the chir pine belt (1,500–1,750 m) share the same heights.
Which one grows depends on rainfall, slope and soil.
Chir pine takes over on drier slopes.
Tree line: the height above which trees cannot grow, because it is too cold and windy. Above it there are only grasses, shrubs, mosses and lichens.
Alpine pastures: natural grasslands above the tree line, at about 3,000–4,000 m and higher. They turn green only in summer, after the snow melts.
Himalayan tundra is caused by height. Arctic tundra is caused by latitude.

Aspect changes the pattern too

Aspect means the direction a slope faces.
South-facing Himalayan slopes are greener.
Monsoon winds from the Bay of Bengal and the Arabian Sea hit the southern face.
Moist air is pushed up the slope and cools, and rain falls on the side facing the wind (the windward side).
North-facing slopes are in rain shadow (the dry side behind a mountain), so they get less rain.
Result: forest is thicker on the south-facing slopes.
So each belt can be denser or thinner at the same height, depending on which way the slope faces.

Where it occurs

Himalayas (about 27°–36°N): the full set of belts, from tropical to tundra.
Foothill deciduous belt: Shiwalik and Terai margins.
Oak–chestnut belt: northeast hills, hilly West Bengal and Uttarakhand.
Chir pine belt: Uttarakhand, where its needles feed spring forest fires.
Deodar: endemic to the western Himalayas, meaning it grows naturally only there. This covers Jammu and Kashmir, Himachal Pradesh, Uttarakhand and nearby areas.
Chinar and walnut: the temperate belt of Kashmir.
Alpine pastures (bugyals): in Uttarakhand, alpine meadows are called bugyals. Examples are Bedni Bugyal and Ali Bugyal in Chamoli district, on the Roopkund trek route.
Transhumance on alpine pastures: transhumance means moving herds up to mountain pastures in summer and down to the valleys in winter.
Gujjars: Jammu and Kashmir, Himachal Pradesh, Uttarakhand (buffalo, cattle)
Bakarwals: Jammu and Kashmir (goats, sheep)
Gaddis: Himachal Pradesh, Dhauladhar range (sheep, goats)
Bhotiyas: Uttarakhand, Kumaon–Garhwal border valleys (sheep, goats, yaks)
Contrast in south India: the Western Ghats, Nilgiris (about 11°N) and Anaimalai hills are mostly about 1,500 m high.
Even the highest peaks are lower than the Himalayan alpine belt: Anamudi (2,695 m, Kerala) and Doddabetta (2,637 m, Tamil Nadu).
So they have only subtropical and temperate belts, with no alpine or tundra belt.
World contrast: the Alps (about 45°–47°N, Europe), where sunshine, not rain, decides which slope is forested.

Don't confuse with

Latitudinal zonation (Arctic tundra): vegetation changes because of distance from the equator. Himalayan zonation is caused by height, so tundra appears at about 4,000 m even at 27°–36°N.
Southern mountain forests (sholas): these are stunted evergreen patches in the Nilgiri, Anaimalai and Palani hills. They have only subtropical and temperate belts, with no alpine or tundra belt.
Aspect in the Alps: in the Alps the sunny south slope is settled and farmed, and the shady north slope stays forested. In the Himalayas the south slope is more forested, because monsoon rain matters more than sun.
Tree line vs snowline: the tree line is where trees stop. Above it, alpine pastures, mosses and lichens still grow below the snowline.

Prelims Hooks

Order from lowest to highest: deciduous forest → oak–chestnut (1,000–2,000 m) → chir pine (1,500–1,750 m) → deodar → blue pine and spruce (2,225–3,048 m) → silver fir, birch, rhododendron (3,000–4,000 m) → mosses and lichens.
Deodar is endemic to the western Himalayas, not the eastern Himalayas. It is a true cedar (Cedrus), and pure stands grow at about 1,900–2,700 m [2].
Chir pine gives resin and timber. Its resin-rich needles drive spring forest fires in Uttarakhand.
Trap: the oak–chestnut belt (1,000–2,000 m) and the chir pine belt (1,500–1,750 m) overlap. Chir pine takes the drier slopes.
South-facing Himalayan slopes have thicker forest than north-facing ones, because they face the monsoon winds.
Bugyal is the Uttarakhand name for an alpine meadow (Bedni, Ali). Pairs to remember: Gaddis – Himachal Pradesh; Bakarwals – Jammu and Kashmir; Bhotiyas – Uttarakhand.

Mains Points

Altitude and aspect control vegetation (GS-I):
Temperature falls with height, so the Himalayas hold belts from tropical forest to tundra.
Monsoon rain makes south-facing slopes wetter and greener.
In the Alps, sunshine is the main control, so the pattern is reversed.
Colonial forestry and fire risk (GS-III):
The British replaced native oak with chir pine, because pine paid more as timber and resin.
Pine's dry, resin-rich needles feed spring fires in Uttarakhand. Fire clears out oak, so pine spreads further and the cycle repeats.
Losing oak weakens hill springs.
Responses include collecting pine needles, bringing back broadleaf trees and community fire watch.
Fragile alpine pastures (GS-I/III):
The alpine belt supports transhumance by Gujjars, Bakarwals, Gaddis and Bhotiyas.
Trekking, camping and overgrazing strip the turf on bugyals such as Bedni and Ali. Bare soil then washes away, and thin alpine soil recovers very slowly.
This calls for limits on how many people and animals a pasture can carry (carrying capacity) and for regulated tourism.

Related concepts

Montane forests: Himalayan zonation and the southern hills

Sources

1Class 11, Ch 5 "Natural Vegetation" (primary)
2Deodar — Britannicabritannica.com · tier 3