booklet 2a Flashcards
where can tropical rainforests be found
tropical rainforests can be found in areas north and south of the equator, with most of them lying between 10N and 10S.
largest tropical rainforest in the world
amazon basin in south america (brazil / peru)
what are the 2 major rainforest regions in china
yunnan / xishuang banna
climatic characteristics of tropical rainforests in terms of temp
high annual mean temp (bc the angle of the sun is large in the tropics throughout the year → large input of solar radiation) [also as the sun is directly overhead on the equator → no winter in equatorial regions]
small annual range of temperature (1C)
little seasonal variation in air temp
hot all year round
climatic characteristics of tropical rainforests in terms of rainfall
high annual rainfall (as large energy inputs create a turbulent and unstable atmospheric condition → convection rain)
little seasonal variation in rainfall
wet all year round
where does convection rain form and where is it commonly found
convection rain forms on heated (ground) surfaces → the most common type of rain that falls in tropical deserts / rainforests
formation of convection rain
formation of convection rain :
1. during daytime intense sunlight heats up the earth’s surface
2. air temp is high near the ground
3. air is heated up and it expands and rises
4. strong vertical air currents form
condensation level
5. air temp falls to dew point and the air becomes saturated
6. excess water vapour in the air condenses and forms clouds
7. cooler air sinks to replace the rising air, forming strong convection currents
8. strong convection currents help water droplets develop into thick and heavy clouds
9. heavy convection rain forms
characteristics of convection rain
- commonly occurs in continental regions + tropical regions during summer
- usually occurs in the late afternoon (as it is hotter then) when the convection current is the strongest
- short duration
- often accompanied by thunderstorms
how do trees in tropical rainforests affect humidity and rainfall?
trees intercept rainfall and absorb large amounts of water from the soil, releasing most of the water thru evapotranspiration → helps the atmosphere stay moist and humid (high humidity in the air favours the formation of clouds and rainfall)
climatic factors
latitude / angle of the sun
distance from the sea
altitude
relief
how does the angle of the sun affect the climate in tropical rainforests
overhead sun for most of the year → high concentration of sunlight), w/ minimum seasonal variation
how do onshore winds affect the climate in tropical rainforests
onshore winds are full of moisture → high relative humidity ++ high temp → high evapotranspiration rate
climate in tropical rainforests
equatorial / tropical humid climate
what is the climate-vegetation relationship
as the amount of annual rainfall decreases, the vegetation cover changes from dense to sparse. there are fewer varieties of plants and fewer layers in vertical structure. the plants become shorter in height and there are fewer trees. the savanna is a transitional region b/w the rainforests and the desert
characteristics of vegetation + plants + animals in tropical rainforests
the hot / wet equatorial climate supports dense forests, w/ many diff kinds of plants growing in the hot + humid environment (TRFs are the habitat of over 50% of the world’s plants / animals) over 5k kinds of plant species and contains ⅓ of the world’s bird species → rich in biodiversity
forest are evergreen and plants grow continuously in the year bc there are no hot/cold/dry/wet seasons
5 layers of the tropical rainforest
emergent
canopy
young tree
shrub
ground
characteristics of the emergent layer
- (up to 50m in height)
- uppermost layer
- trees are very tall and have straight tree trunks
- crowns are in an umbrella shape
- widely spaced
characteristics of the canopy layer
- a layer of dense + tall trees
- oval shaped crowns that are closely packed / overlapping → continuous
- long + wide branches → absorb sunlight
- blocks up to 90% of sunlight
characteristics of the young tree layer
- (seldom exceed 15m in height)
- fairly dark in this layer bc sun rays are blocked by the canopy layer
- plants are short + thin + widely spaced (as sunlight provides nutrition; less sunlight → thinner + shorter)
- conical crown
- have much larger leaves compared to those in the canopy layer to absorb sunlight for nutrition
- saplings need to wait for larger plants / trees to die so they can grow into the gap in the canopy
- trunks are slender + slim
characteristics of the shrub layer
- (less than 5m in height)
- dark, as it is below the young tree layer
- high relative humidity (it is much cooler compared to the top 3 layers)
- some shrubs / ferns / other pants which don’t need much sunlight can be grown here
- humid, low evaporation rate (microclimate)
characteristics of the ground layer
- (surface / forest floor)
- very dark and damp
- little vegetation (few plant can survive only moss / fungi)
- many creepy crawly animals
- rotting leaves + dead animals accumulate to form a layer of dead organic matter → litter
- soil is infertile bc the large amount of rain → minerals + nutrients are washed away
features of leaves in tropical rainforests and its purposes
- broad leaves (especially in lower layers) → to absorb more sunlight
- drip tip → shed water quickly
- waxy surface → waterproof
features of roots in tropical rainforests and its purposes
- buttress roots (big roots on the side of the trees) → helps to support the tree + prevent it from falling
- shallow + extensive roots → strong competition w/ other vegetation + shallow soil in TRF → dense short shallow roots help absorb nutrients + water on / near the surface
- aerial roots → grown from plant stems / leaf tissues
features of trunks in tropical rainforests and its purposes
- straight tree trunk so they can grow tall
- branchless + smooth → more water falls down / run off from the top of the tree ++ put efforts into growing tall to gain more sunlight
special plants in tropical rainforests
epiphytes
climbers
stranglers
parasites
what are epiphytes
live on other plants for support (as they can survive w/o soil)
can grow above ground level → for access to sunlight
harmless to host plant
what are climbers + give example
woody plant
located in the soil at ground and use trees / other means for vertical support
wind their way up the trees to the canopy to get access to well lit areas
eg. liana
what are stranglers
compete w host tree for sunlight space and nutrients → absorb all nutrients from the tree
harmful to host
takes up the space of the host tree to avoid competition (also known as killer trees that start life as epiphytes)
what are parasites
plants that do not produce their own food but instead obtain their food from the host plant
what lifestyles do indigenous tribes lead and why
indigenous ppl have a subsistence lifestyle, bc they hunt and grow only what they need to subsist / survive
process of the slash and burn farming method
- farmers from an indigenous tribe choose a suitable site in the rainforest
- small area of land in the forest is cleared (by cutting down trees to burn them) by burning the vegetation
- farmers spread the ash over the cleared soil (as rainforest soil is rather infertile, ash acts as a natural fertiliser to increase soil fertility)
- they start planting crops on the soil, and they grow well in the nutrient rich soil
- after 4-5 years the nutrients in the soil are exhausted and crop yield drops
- farmers move onto a new area of forest. the old plot is left fallow to recover its vegetation as the nutrient cycle is restored
characteristics of slash and burn farming system
arable / extensive / subsistence / low-tech / non-sedentary
why is the vegetation burned after the plot is cleared
farmers burn the vegetation once the plot has been cleared to remove tree stumps etc. + ash acts as a good fertiliser for the farmers afterwards → improve yield / fertility / productivity
why do indigenous tribes need to move around
need to move bc crop yield is reduced when the land is exhausted of nutrients
what is an alternative name for the slash and burn method
the method of shifting cultivation
