Montane forests: Himalayan zonation and the southern hills

Detail

1. What montane forests are and why they change with height

• Montane forests are the forests of mountains. Their type changes as you go higher.
• Why it happens:
• Air gets cooler as you climb. Temperature falls with altitude (height above sea level).
• Cooler air changes how much heat and moisture plants get.

• So different plants grow at different heights. They form belts that sit one above the other.

• Climbing a high mountain is like travelling from the equator towards the poles. You can see tropical, temperate and polar-type (tundra) vegetation on a single slope.

• NCERT splits them into two groups:
• Northern mountain forests (the Himalayas)
• Southern mountain forests (Western Ghats, Vindhyas, Nilgiris)

2. Altitudinal zonation of Himalayan vegetation

• Altitudinal zonation means plants are arranged in belts by height. Each belt has its own climate and its own plants.
• The Himalayas 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.

Altitude	Climate type	Vegetation	Where / use
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	Northeast hills, hilly West Bengal, Uttarakhand
1,500–1,750 m	Warm temperate	Chir pine	Main commercial tree: timber and resin
Temperate zone (higher)	Temperate	Deodar, chinar, walnut	Deodar for building; chinar and walnut support 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

• Note on overlap: the wet temperate belt (1,000–2,000 m) and the chir pine belt (1,500–1,750 m) overlap. 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.
• Tundra: cold, treeless land where only mosses, lichens and small plants survive. In the Himalayas it comes from height, not from latitude as in the Arctic.

3. Key trees of the Himalayan belts

Chir pine

• Chir pine is a needle-leaved conifer (a cone-bearing tree with needle leaves). It grows at 1,500–1,750 m.
• It is the main commercial tree of its belt:
• Timber, used for building and furniture

• Resin, a sticky sap used to make turpentine and rosin

• How chir pine spread and why it fuels fires:

• In colonial times the British planted chir pine in place of native oak, because pine paid more as timber and resin.
• Chir pine drops large amounts of dry needles full of resin. These carpet the forest floor.
• In the dry, hot spring (before the monsoon), these needles catch fire easily. This feeds spring forest fires in Uttarakhand.

• Fire clears out broadleaf plants such as oak. This helps pine spread further, so the cycle repeats.

• Oak forests hold water and feed springs. Losing oak to pine makes hill water sources weaker.

Deodar

• Deodar (Himalayan cedar, Cedrus deodara) is one of the true cedars of the genus Cedrus [2].
• It is endemic to the western Himalayas. This means it grows naturally only there (Jammu and Kashmir, Himachal Pradesh, Uttarakhand, and nearby areas).
• Pure stands of deodar grow at about 1,900–2,700 m (6,300–9,000 ft) [2].
• Its wood is strong and lasting, and it resists rot. It is used for buildings, bridges and railway sleepers.

Chinar and walnut

• Chinar (Oriental plane) and walnut grow in the temperate belt of Kashmir.
• They support Kashmir handicrafts: carved walnut-wood furniture and boxes; chinar wood and motifs.

Alpine trees

• Silver fir, juniper, pine, birch and rhododendron grow at 3,000–4,000 m.
• Trees here grow short and twisted near the tree line, because of cold, wind and a short growing season.

4. Aspect: why south-facing Himalayan slopes are greener

• Aspect means the direction a slope faces (north, south, east or west).
• How the Himalayan pattern forms:
• The south-west monsoon winds blow in from the Bay of Bengal and the Arabian Sea and hit the southern face of the Himalayas.
• Moist air is pushed up the slope. It cools, and it rains on the south-facing side (the windward side, the side facing the wind).
• The north-facing slopes lie on the far side of the ranges. They get less rain (they are in rain shadow, the dry side behind a mountain).

• Result: south-facing slopes carry thicker forest than the drier north-facing slopes.

• Contrast with the Alps (about 45°–47°N, Europe):

• In the Alps there is no monsoon. The main control is sunlight.
• The sunny south-facing slope is warmer, so people use it for villages, farms and vineyards.
• The shady north-facing slope is cooler and stays under forest.
• So in the Alps, forest is often thickest on the shady north side. In the Himalayas it is thickest on the south side, because rain matters more than sun there.

Feature	Himalayas	Alps
Main control	Rain from monsoon winds	Sunshine
South-facing slope	Wetter, denser forest	Sunny, settled, farmed
North-facing slope	Drier, thinner forest	Shady, forested

5. Alpine pastures and transhumance

• Alpine pastures are natural grasslands above the tree line, at about 3,000–4,000 m and higher. They are green only in summer, after the snow melts.
• Transhumance means moving herds with the seasons. Herders go up to high pastures in summer and come down to valleys in winter.

Community	Main area	Animals
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

• Bugyals: in Uttarakhand, alpine meadows are called bugyals. Examples are Bedni Bugyal and Ali Bugyal (Chamoli district, on the Roopkund trek route).
• Pressures on bugyals:
• More trekking and camping trample the turf.
• Overgrazing removes the grass cover.
• Bare soil then washes away on steep slopes. The thin alpine soil takes a very long time to recover.

6. Southern mountain forests

• They grow in the Western Ghats, Vindhyas and Nilgiris, mainly in Kerala, Tamil Nadu and Karnataka.
• Why they differ from the Himalayas:
• These hills are closer to the tropics. The Nilgiris lie at about 11°N, so the base climate is warm.
• They are only about 1,500 m high in general. A few peaks are much higher: Anamudi (2,695 m, Anaimalai hills, Kerala) and Doddabetta (2,637 m, Nilgiris, Tamil Nadu).
• Result: forests are temperate at higher levels and subtropical lower down. There is no alpine or tundra belt.

Feature	Northern (Himalayan)	Southern hills
Latitude	~27°–36°N	~8°–22°N
Height	Up to 8,000 m+	Mostly ~1,500 m; highest peaks ~2,700 m
Belts	Tropical to tundra	Subtropical to temperate only
Typical forest	Oak, chir pine, deodar, spruce, fir	Shola, with magnolia, laurel, cinchona, wattle
Grassland	Alpine pastures (bugyals)	High montane grassland around sholas

7. Shola forests

• Shola forest is made up of patches of stunted (short, slow-growing) evergreen forest. They grow in sheltered folds (valleys and hollows) of the Nilgiri, Anaimalai and Palani hills. Open high grassland surrounds them.
• The forest patches and the grassland together make a shola-grassland mosaic (a patchwork of the two habitats).
• The patches grow in hollows that are protected from the wind and hold more moisture. The open ridges and slopes stay as grassland.
• Important trees:
• Magnolia and laurel: native evergreen trees
• Cinchona: its bark gives quinine, a medicine for malaria

• Wattle: an introduced tree whose bark gives tannin (used to tan leather)

• Similar forests grow in the Satpura and Maikal ranges of central India.

Beyond NCERT: shola-grassland as a water sponge

• How the sponge works:
• The grassland and the shola soil soak up monsoon rain.
• They release the water slowly through the year.

• This feeds streams and rivers that flow down from the Western Ghats.

• The threat:

• Tea, eucalyptus and wattle plantations have replaced much of the grassland.
• Wattle spreads by itself into open grassland.
• With the grassland gone, the sponge works less well, and the hill streams carry less water in the dry season.

Prelims Hooks

• Order by height (lowest to highest) in the Himalayas: 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.
• South-facing Himalayan slopes are more thickly forested than north-facing ones, because they face the monsoon winds.
• Bugyal is the name for an alpine meadow in Uttarakhand. Examples are Bedni and Ali Bugyal.
• Community–state pairs: Gaddis – Himachal Pradesh; Bakarwals – Jammu and Kashmir; Bhotiyas – Uttarakhand; Gujjars – across the western Himalayas.
• Sholas are found in the Nilgiri, Anaimalai and Palani hills. Similar forests grow in the Satpura and Maikal ranges.
• Trap: cinchona and wattle are listed among the shola's economically important trees, but wattle is an introduced species that now invades the grassland.
• Chinar and walnut are linked to Kashmir handicrafts.

Mains Points

• Altitude and aspect control vegetation (GS-I): temperature falls with height, so the Himalayas hold tropical to tundra belts. Monsoon exposure makes south-facing slopes wetter and greener. In the Alps the controlling factor is sunshine instead, so the pattern is reversed.
• Colonial forestry and fire risk (GS-III): the British replaced oak with chir pine for timber and resin. Pine's resinous needle litter now feeds spring fires in Uttarakhand, oak's water-holding role is lost, and hill springs weaken. Answers to this include collecting pine needles, bringing back broadleaf trees, and community fire watch.
• Fragile high-altitude commons (GS-I/III): alpine pastures support transhumance by Gujjars, Bakarwals, Gaddis and Bhotiyas. Bugyals such as Bedni and Ali suffer from trekking and overgrazing, which calls for carrying-capacity limits and regulated tourism.
• Shola-grassland as water infrastructure (GS-III): sholas act as sponges that feed peninsular rivers. Tea, eucalyptus and wattle plantations have taken over much of the grassland. Restoration means removing invasive species and protecting the grassland as well as the forest patches.