Geography: Types of Natural Vegetation

Natural vegetation: plants that grow with little or no human interferance.
Ecosystem: community of living organisms
Biome: the living part of an ecosystem

Forests: Tropical Rainforest, Temperate Deciduous Forest, Temperate Coniferous Forests
Grasslands: Tropical Grassland and Temperate Grassland
Deserts: Hot desert and Cold desert  (tundra)

Climate: the atmospheric condition of an area over a considerable period of time
               ~Temperature and Precipitation
Global Distribution of Natural Vegetation: closely related to the latitudes.


Tropical Rainforest:
-tropical equatorial climate
-high temp: about 27 dc
-high rainfall: above 1500mm
-constant throughout the year
-between 10 d N & S of the EQ
-Amazon basin, Congo Basin and SEA Basin

~Structure of Forest
[] 5 Vertical Layer
[] Emergent Layer: 30-50m. Crowns above the canopy layer
[] Canopy Layer: 15-30m. Umbrella-shaped crowns, wide and shallow, forms a continuous leaf cover.
[] Understorey Layer: 6-15m. narrower, oval-shaped crowns, grow where gaps in the canopy layer allow sunlight to pass through.
[] Shrubs layer: up to 6m. Tree saplings and woody plants
[] Undergrowth Layer: Max 5m. Grasses, mosses, ferns and fungi. Very little sunlight reaches this layer.

Epiphytes: Bird's Nest Fern and orchids. Grow on trees for physical support. Rainwater and decaying leaves provides nutrients and water for the plant.
Lianas: Thick woody vines that wind around trees to reach for sunlight. Up to 90m in length.
Parasitic Plants: strangling fig wraps itself around the trunk of its host tree to compete for space, sunlight and nutrients. Cause the death of the host tree.
Fungi thrive in dark, moist places conditions. Grows and feeds on decomposed fallen logs.
Leaf litter forms a layer of humus.

~Diversity of plant species
750 tree species and 1500 other plants species per hectare.

~Density
Extremely dense. Grows very closely to one another. Abundant vegetation.
Due to high temp. and rainfall throughout the year.

~Leaves
Evergreen, constant high rainfall.
Do not shed leaves.
Broad to maximise surface area for photosynthesis.
Waxy with drip tips, to allow rainwater to drain off easily. Prevents harmful bacteria from growing.

~Flowers and Fruits
Produce fruit throughout the year.
Colourful and sweet-smelling, to attract insects for pollination and animals for seed dispersal due to the still air below the canopy.

~Bark and Branches
Thin and smooth barks.
Branches only at the top 1/3 portion of trunks.

~Roots
Shallow and spread widely as they do not need to reach deep into the soil for nutrients.
Buttress roots, to support the great weight of trees.


Tropical Monsoon Forest:
-tropical monsoon climate
-high temp: about 26 dc
-high rainfall: over 1500 mm
-distinct wet and dry seasons.
-between 10 d & 25 d N & S of the EQ
-Mangalore

~Structure of Forest
[] 3 Vertical Layer
[] Canopy Layer: 15-30m. More spread out.
[] Understorey Layer: 6-15m.
[] Undergrowth: Max 6m. Bamboo thickets and grasses grow densely during wet, but sparse during dry season.

~Diversity of Plants
Around 200 species of plants per hectare. Due to inconsistent rainfall

~Density
Abundant and more spreaded. Crowns do not interlock. Dense undergrowth. Luxuriant during wet season.

~Leaves
Deciduous, shed leaves during dry season to minimise water loss through transpiration.
Waxy with drip tip.
Narrow leaves of bamboo plant.

~Flowers and Fruits
Bear fruit during dry season while they are leafless.

~Bark and Branches
Thick and coarse to protect the tree from heat and dryness during dry season. Withstand extreme heat from natural forest fires.
Branches are located at the middles of trunks. Sunlight is able to reach the lower parts of the forest.


Mangrove Forests:
-tropical climate
-coastal areas
-high temp: about 20 dc-30dc
-high rainfall: 1000-2000mm
-between 23.5 dc N & S of the EQ

~Structure of Forest
[] 3 Horizontal Zones
[] 2-40m. Average height: 15m. Muddy soil cannot support tall trees
[] Coastal Zone: nearest to the sea. Adapted to saltwater. Flooded during high tide. Breathing/aerial roots. Avicennia and Sonnaratia
[] Middle Zone: Prop/stilt roots. Rhizophora
[] Inland Zone: Least tolerant to saltwater. Knee-like roots. Bruguiera

~Diversity of plants
HALOPHYTES

~Density
Dense and luxuriant due to high temp and rainfall. Continuous canopy, compete for sunlight.

~Leaves
Evergreen. No seasonal change.
Broad with drip tip. Allow water to flow off easily.
Thick and leathery. Reduce water loss through transpiration.
Salt secretors, Avicennia: secretes excess salt on their leaves which are removed by wind or rain.
Salt filtrators, Sonnaratia, Rhizophora, Bruguiera: absorbs salt and removes excess salt by storing it in old leaves which then fall off.

~Flowers and Fruits
Colourful to attract insects for pollination.
Buoyant, float on water to be washed away to a new coastal area.
Fruits of the Rhizophora germinate while they are still on their parent tree and drop directly on the ground to take root. Elongated structure with sharp tips.

~Roots
Aerial roots exposed duting low tide, allows to take in oxygen.
Prop/stilt roots provides support for the trees on muddy soil.
Kneed roots provides support for trees on soft soil.


Coniferous Forest:
-cool temperate continental climate
-60 d & 70d N of EQ.
-experience seasonal change
-summer: 21 dc
-winter: -40 dc
-precipitation:  300-635mm throughout the year.
-Scandinavia, USA

~Structure of Forest
No distinct layer. Grow generally uniform height (20-30m). Grow close together.
Little undergrowth. Low amount of sunight.

~Diversity of plant species
Only a few. Pine, spruce and fir. Trees grow in pure stands or a mix of 2-3 species in an area.

~Density
Low temp and precipitation cannot support dense vegetation.

~Leaves
Do not shed leaves.  So that photosynthesis can still take place whenever temp rises above 6 dc.
Needle-like leaves have small surface areas that help to reduce water loss through transpiration. Store water for use during winter.

~Flowers and Fruits
Trees bear cones, part of the reproductive system. Female cones produce seed while male cones produce pollen. Dispersed by wind or animal.

~Bark and Branches
Thick barks to protect them from long cold winter. Flexible branches that slope downwards to enable snow to slide off easily.
Conical shape of trees also helps them to withstand strong winds.

~Roots
Trees have shallow, spreading roots which enable them to absorb water from melting snow.