2.5 - Climate and Natural Vegetation Flashcards
Climate
Average weather conditions over a long period of time in a specific region
Location of hot deserts
- 15° - 30° north and south of the equator (tropical and sub-tropical)
- North Africa - Sahara, Southern Africa - Kalahari and Namib, Australia. Middle East
Annual percipitation in hot deserts
below 250 mm
Temperature range in hot deserts
- Daytime temperatures can reach 50°C but average around 25°C
- Night-time temperatures below 0°C
- Diurnal range is large up to 45°C
- Annual range is around 15°C
Seasons in hot deserts
Summer and winter
Humidity in hot deserts
Low often between 10-30%
What factors influence the climate of hot deserts?
- High pressure all year which means the air is descending and warming so precipitation does not occur because the air is not rising
- Prevailing winds are often from over land masses which means they contain little moisture
- Some deserts are in a rain shadow so there is little rainfall
- Cold ocean currents on the west side of continents may reduce summer temperatures due to the cooling effect of the ocean
Rain shadow
The prevailing wind travels across the mountains and sinks on the leewards (wind sheltered) side. This means there is no rising air and so no rainfall.
Explain the Hadley Cell
- Air rises at the equator and when it reaches the upper atmosphere it moves north and south
- The air cools and starts to sink
- This creates a zone of high pressure at about 30 degrees north and south of the equator
- Due to the sinking air, warm air cannot rise, condense and form clouds. This results in high aridity
Adaptations and their explanations of camels
- long eye lashes, hairy ears and closing nostrils help to keep out sand
- thick eyebrows which stand out and shade eyes from the sun
- wide feet so they don’t sink in the sand
- they can go without water for over a week because they can drink gallons in one go
- they can go months without food - they store fat in their humps
- body temperature can change to avoid losing water through sweating
- they are well camouflaged
- thick fur helps to keep them warm at night
Adaptations and their explanations of cacti
- thick, waxy skin to reduce loss of water and to reflect heat
- large, fleshy stems to store water
- thorns and thin, spiky or glossy leaves to reduce water loss due to their small surface area
- spikes protect cacti from animals wishing to use stored water
- deep roots to tap groundwater
- long shallow roots which spread over a wide area
- plants lie dormant for years until rain falls
Food web
System of interconnected food chains
Food chain
shows the different species of an organism in an ecosystem, and what eats what
Consumer
an animal that eats a plant or another animal
Producer
An organism that makes food. This is usually a green plant, because plants can make their own food by photosynthesis
Describe the soil profile of a hot desert
- Desert soils are thin, sandy, rocky and generally grey in colour
- Desert soils are very dry
* When it does rain they soak up the water very quickly - The surface of the soil may appear crusty. This is due to the lack of rainfall.
- As it is so hot water is drawn up to the surface of the soil by evaporation
- As the water evaporates, salts are left behind on the surface of the soil.
- There is a surface layer of sand or pebbles, with low hummus levels in it.
- This is followed by a dry brown-reddish layer, as you get deeper this contains fragments of rock.
- Then there is solid rock.
How are plants and soil interdependent in a desert climate?
- Plants rely upon soils for their nutrients
* the soils rely upon plants to provide extra nutrients through dead vegetation and fixing chemicals from the air into the soil - Plants help soils retain more water, by providing shade from the searing desert sunlight
- Plants tie the soil together, preventing soil erosion and excessive leaching of nutrients in wetter periods
- Oases exist in low points in the desert
* where water can be found closer to the surface and some agriculture is possible
What is a tropical rainforests and its characteristics (4)?
The Tropical Rainforest is a forest occurring in tropical areas of heavy rainfall.
Characteristics
* abundant with many species of wildlife and vegetation
* cover less than two percent of the Earth’s surface
* home to some 50 to 70 percent of all life forms on our planet
* are the most productive and most complex ecosystems on Earth.
Location of tropical rainforests
Tropical rainforests are located between 10°N and 10°S of the Equator
* largest rainforests are in the Amazon in Brazil (South America), Demographic Republic of Congo (Africa) and Indonesia (South East Asia) and are also found in Hawaii and the islands of the Pacific & Caribbean
Annual percipitation in tropical rainforests
over 2000 mm
Temperature range in tropical rainforests
- low range of mean monthly temperatures - 26-28°C
- Constant high temperatures
- Diurnal range is about 7 degrees celcius
Seasons in tropical rainforests
No seasons - hot and wet all year round
Humidity in tropical rainforests
High - usually over 75-80%
Factors influencing the equatorial climate (4)
- The midday sun is almost directly overhead all year meaning there is maximum insolation
- Low pressure all year which leads to rising air, condensation, cloud formation and high precipitation levels
- Dense vegetation cover leads to high levels of evaporation and transpiration
- The warm air stores large amounts of water vapour until the temperatures start to cool in late afternoon which then leads to heavy, daily convectional rainfall
Explain trade winds
Winds blow into the equatorial region from high pressure areas to the north and south.
The winds from the north blow from the north-east and the winds from the south blow from the south-east
Explain convectional rainfall
When the land warms up, it heats the air above it. This causes the air to expand and rise. As the air rises it cools and condenses. If this process continues then rain will fall.
Describe the soil of tropical rainforests
- Most of the soil is not very fertile.
- A thin layer of fertile soil is found at the surface where the dead leaves decompose
* It is red in colour because it is rich in iron. - Due to heavy rainfall the nutrients are quickly washed out of the soil.
Layers of vegetation in tropical rainforests
- Ground level
- Shrub layer
- Under canopy
- (main) canopy
- Emergents
Emergents
The tallest trees and are usually over 50 metres tall.
* e.g. The Kapok tree
(main) Canopy
The sea of leaves blocking out the sun from the lower layers.
* it contains over 50% of the rainforest’s wildlife (e.g. birds, snakes and monkeys)
Under canopy
Mainly contains bare tree trunks and lianas
Shrub layer
Has the densest plant growth
* contains shrubs and ferns and other plants which need less sunlight
* samplings of emergents and canopy trees can also be found here
Ground layer
The forest floor is usually dark and damp
* it contains a layer of rotting leaves and dead animals called litter
* this decomposes rapidly (within 6 weeks) to form a thin humus, rich in nutrients
* below this upper soil layer the soil lacks nutrients
* this is because nutrients are rapidly absorbed by vegetation
Biosphere
the surface of the earth made up of plants, animals living or have lived
Ecosystem
the interaction between the living (plants and animals) and non-living (sunshine, air, water, rocks) components
Biomes
Large scale global ecosystems e.g. TRF or desert
Biodiverse
the wide range of living things (flora and fauna) that an ecosystem supports
Leaching
Soils in the rainforest are mainly thin and poor. Nutrient levels in the soil are low due to the leaching (washing away of nutrients) by the heavy equatorial rain. This leaching means that the lower layers of the soils lack the nutrients and minerals the lush vegetation needs.
The nutrient cycle in tropical rainforests
- Heavy rain each day is intercepted by canopy
- Many leaves fall
- Leaves decay rapidly to form humus
- Nutrients added to the soil by leaching
- Rich soil
- Rapid tree growth
Adaptations of Lianas
These are woody vines that have roots in the ground but climb up the trees
* This is to reach the sunlight. Their leaves and flowers grow in the canopy.
Adaptations of Tree Trunks
Trunks are tall and thin
* This allows trees to reach the sunlight. The bark on these trees is smooth to allow water to flow down to the roots easily.
Adaptations of Buttress Roots
Large roots have ridges
* This creates a large surface area that help to support large trees.
Adaptations of Drip Tips
Plants have leaves with pointy tips.
* This allows water to run off the leaves quickly without damaging or breaking them.
Adaptations of Epiphytes
These are plants which live on the branches of trees high up in the canopy
* They get sunlight from the canopy while they get their nutrients from the air and water, not from the soil.
Adaptations of Sloth
The sloth uses camouflage and moves very slowly
* This makes it difficult for predators to spot.
Adaptations of Spider Monkey
The spider monkey has long, strong limbs and a prehensile tail
* This to help it to climb through the rainforest trees. To find food and escape predators
Adaptations of Flying Frogs
The flying frog has fully webbed hands and feet, and a flap of loose skin that stretches between its limbs
* This allows it to glide from plant to plant to find food and evade predators on the ground below.
Adaptations of Toucan
The toucan has a long, large bill
* This allows it to reach and cut fruit from branches that are too weak to support its weight.
Adaptations of Jaguar
They are excellent swimmers, camouflage fur and large claws
* This helps them to be an effective hunter, and climb tress to catch prey.
Reasons why Tropical Rainforests are important (3)
- Regulate the composition of the atmosphere - this helps to offset the effect of climate change by taking in carbon dioxide through photosynthesis and releasing oxygen
- Influence the hydrological cycle - rainforests provide water for people. Trees act as a water store by intercepting rainfall. They release water into the atmosphere by evapotranspiration. Tree roots also increase infiltration, allowing increased amounts of water to percolate to groundwater stores and develop aquifers
- ** Maintain soil health ** - TRFs produce rich fertile top soils due to the rapid leaf fall and decomposition which rapidly recycles nutrients. These soils can be used to grow cassava and maize which is the staple diet of the local people.
Deforestation
The permanent destruction of forests in order to make the land available for other uses
Global statistics of deforestation of tropical rainforests
- Rainforests once covered 14% of the Earth’s land surface now they only cover 6%
- It is estimated that 137 plant, animal and insect species are lost every day due to deforestation
- Experts estimate the remaining rainforests could be lost in under 40 years
6 causes of deforestation of tropical rainforests
- hydroelectric power
- agriculture and farming
- mining
- settlements
- logging
- road building
How does hydroelectric power cause deforestation?
Building of dams and reservoirs to provide electricity on the Amazon Basin has resulted large areas of forest being flooded.
* e.g. The flooding of the Balbina dam in Brazil resulted in the loss of 920 square miles of tropical rainforest.
How does logging cause deforestation?
Trees are cut down for timber
* Tropical rainforests are cut down so that valuable trees like mahogany can be accessed and sold for timber to make furniture.
* Other trees are cut down for making paper products.
How does mining cause deforestation?
There is clearance of land to obtain precious minerals
How does road building cause deforestation?
The construction of access roads for farmers, loggers and miners results in large parts of the tropical rainforest being destroyed
How do settlements cause deforestation?
As populations grow, more space is cleared for housing and construction space.
How does agriculture and farming cause deforestation?
Huge areas are cleared for plantations such as soy or palm oil as well as cattle
* these areas are used both for arable and pastoral farming
