Definition of natural vegetation:
Plants that grow naturally in a place with little or no human interference.
Major types of natural vegetation:
=biome (the living or biotic part of an ecosystem, referring to both plants and animals found in an ecosytem)
1. forest biome (mainly trees, many varieties)
A. tropical rainforest
B. temperate deciduous forest
C. coniferous forest
2. grasslands (mainly grass, few varieties)
A. tropical grassland
B. temperate grassland
3. deserts （mainly sparse vegetation——scrubs, tough grasses in hot/ mosses, lichens in cold. Few varieties）
A. hot desert vegetation
B. cold desert vegetation (tundra)
What is climate?
Definition:
the atmospheric conditions of a specitic place over a considerable period of time.
Two main elements that affect plant growth:
Temperature
Precipitation
High——forest
moderate——grassland
little or no——desert
tropical rainforests
location:
near the Equator, between 10N and s of the euator
@ the Amazon Basin in South America, the Congo Basin in Africa and parts of Southeast Asia
features
high temperatures(27) and rainfall (1500ml/year)
structure of the forsest
emergent layer 30-50m tall, thick and straight trunks
canopy layer 15-30m wide, shallow and umbrella-shaped crowns——prevent sunlight
epiphytes, lianas and parasitic plants
understorey layer 6-15m narrower, oval-shaped crowns
parasitic plants
shrub layer up to 6m tree saplings and woody plants
undergrowth layer max 5m grasses, ferns, mosses and fungi
diversity of plant species
more than 750 species of trees and 1500 species of other plants (largest)
density
extremely dense
leaves
evergreen
waxy with drip tips
flowers and fruits
produce fruits throughout the year
colourful and sweet-smelling to attract insects for pollination and animals for seed dispersal
bark and braches
thin and smooth barks
branch only on the top one-third portion of the trunks
roots
shallow and spread widely
(buttress roots)
Tropical monsoon forests
Location
Places that experience the tropical monsoon climate, between 10-25 N and S
@ South Asia, Southeast Asia, southern China and northern Australia
Features
High temperatures(26)
rainfall(1500ml/year) with distinct wet and dry seasons
strictire of the forest
canopy layer
understorey layer
undergrowth layer
diversity of plant species
fewer than rainforest
density
less dense than rainforest
leaves
deciduous (shed during the dry season)
waxy with drip tips
flowers and fruits
flower and bear fruit during the dry season
bark and branches
thick and coarse bark
branches located around the middle of the trunks
roots
deep
Mangrove forests
Location
Places that experience the tropical climate, along sheltered coastal regions and places where rivers constantly deposit clay and silt, between 23.5 N and S
Structure of the forest
Three distinct horizontal zones
1. coastal zone growing in salt water, having breathing roots or aerial roots
2. middle zone prop roots or stilit roots
3. inland zone knee- like roots
diversity of plant species
salt-tolerant plants known as halophytes
four main species
density
dense and luxuriant
leaves
evergreen
broad with dirp tips
thick and leathery surfaces
flowers and fruits
colourful to attract insects to pollinate its flowers
roots
aerial roots k=prop roots and kneed roots
coniferous forests
location
between 60-70N
@ Alaska, northern Canada, northern USA, northern Scaninavia and Russia
features
temperatures can fall to -40 summer temperatures averaging 21
precipitation is often in the form of snow (300-635ml/year)
structures of the forest
no distinct layers 20-30m uniform in height
diversity of plant species
only a few
only a single species or a mix of at most two to three species grow in and area of coniferous forest
density
not dense
leaves
evergreen
needle-like leaves
flowers and fruits
cones
bark and branches
thick braks
flexible branches
roots
shallow, spreading roots
没有评论:
发表评论