Natural Vegetation- Geography

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  • Topic: Root, Mangrove, Water
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Natural Vegetation

Tropical Rainforests
10º North and South of the Equator
High rainfall and temperatures (over 1500 mm yearly; about 27º) Typically located in the Amazon Basin in South America, Congo Basin in Africa and parts of Southeast Asia such as Indonesia and Malaysia. ~400 species per hectare

5 distinct layers:
Emergent: 30m to 50m; tall thick straight trunks
Canopy: 15m to 30m; wide, shallow, umbrella-shaped crowns form a continuous leaf cover, preventing sunlight from penetrating into the lower layers Understorey: 6m to 15m; narrower, oval-shaped crowns, trees grow where gaps in the canopy allow sunlight to penetrate Shrub: Up to 6m; Tree saplings and woody plants

Undergrowth: Up to 5m; Fungi, mosses, grass, ferns

Epiphytes: grow along tree branches to get more sunlight (e.g. Birds’ nest fern and orchids)

Lianas: thick woody vines that wind around trees for sunlight (up to lengths of 90m)

Parasitic plants: Strangling fig wraps itself around the trunk of the host tree and competes with it for nutrients and sunlight, eventually killing the host tree

Leaf litter: leaves that fall from trees decompose quickly to form a layer of humus

Humus: rich in nutrients, supports abundant vegetation growth

Making furniture and other objects: Keruing, meranti, chengal, kapur (species of trees)

Tropical rainforests are extremely dense.

Leaves are:
evergreen,
large and broad to increase surface area for photosynthesis
waxy with drip tips to allow rainwater to drain off easily, preventing harmful bacteria from growing. (Protects the plant from diseases; the high rainfall and temperature of the tropical rainforest promote rapid growth of bacteria)

Flowers are colourful and sweet-smelling to attract insects for pollination and animals for seed dispersal.

Bark and Branches:
barks are thin and smooth (no need for protection against weather) branches only on the top 1/3 of the trunks

Roots:
shallow and spread widely(do not need to reach deeply for water and nutrients) some have buttress roots (thick and spread out widely to support the great weight of trees) Tropical Monsoon

High temperatures(about 26º) and rainfall (over 1500mm yearly) Distinct wet and dry seasons
10º N and 25º S of the Equator
~200 species per hectare

3 layers:
Canopy: 15m to 30m in height; more spread out than in Tropical RF; epiphytes, lianas, parasitic plants here Understorey: 6m to 15m
Undergrowth: Up to 6m; bamboo thickets and grasses grow densely

Most trees are commercially available hardwoods, sal, teak and sandalwood. sal for fuelwood, sandalwood for incense making.

Crowns do not interlock to form continuous canopy.

Wet season: more dense
Dry season: sparse (plants shed their leaves)

Leaves:
are deciduous (shed during dry season to minimise water loss due to transpiration) are waxy with drip tips to allow rainwater to drain away to prevent the growth of bacteria and protects the plants from diseases (high temp. and rainfall of the tropical climate promotes rapid growth of bacteria)

e.g. narrow leaves of the bamboo plant minimise water loss through transpiration (adaptation for dry season)

Trees will flower and bear fruit during the dry season

thick and coarse bark protects the tree from the heat and dryness during the dry season (e.g. prevents forest fires)

Branches are located at the middle of trunks.

Deep roots to tap water sources deep underground.
Mangroves

23.5ºN and S of the Equator

Horizontal layers:
Costal-> Middle -> Inland Zones

Coastal: Avicennia and Sonneratia, adapted to growing in saltwater= breathing roots or aerial roots

Middle: Rhizophora, prop roots or stilt roots

Inland: Bruguiera, knee-like roots

mangroves are dense and luxuriant with a dense continuous canopy, undergrowth is thus sparse

Leaves are broad with drip tips, and are also thick and leathery to minimise water loss due to transpiration

Avicennia: Salt...
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