Geography [[Weather and Climate]] 4.2

[[4.2 Features and Climates of an ecosystem]]

*Rainforest
- high hummidity
- 29-30
- range = 4 degrees
- rain all year
- 2000 mm rain per year
- Tall, broad evergreen trees
- canopied forests with layered structure
- rapid nutrient cycling
- biomas 45.0jg/m

*Savanna Forest
- 23-33
- range = 10 degrees
- 10 months of rainfall
-800-900mm rain per year
- mixed grasslands with trees
- clearings of woody shrubs and tall trees
- drought resistant trees
- biomass 9.0kg/m

*Savanna Grassland
- 23-33
- range = 10 degrees
- 7 months of rainfall
-800-900mm rain per year
- mixed grasslands with trees
- clearings of woody shrubs and tall trees
- drought resistant trees
- biomass 9.0kg/m

*Sahel Scrubland/Semi Desert
- 22-36
-range=14 degrees
- 3-5 months of rainfall
- 300-500 mm rain per year
- Tall Savanna grass
-Isolated drought
- protection agaisnt fire/animal predators
- biomas 4.0

*True Desert
- 10-40
- range = 30 degrees
- 0mm annual precipitaion
- low humidity
- 0-100 (flash floods) rain per year
- Xerophytic plants to adapted to arid conditions
- limited species
- Biomas 0.6 kg/m

Geography [[Weather and Climate]] 4.2

[[4.2 What management problems does the seasonality of climates cause?]]

Life styles are completely controlled by the need to find water, and the need to know where the nearest supply of water is should the original source fail.
Thus, one of the main management problems is the management of water.

There are three types of Rivers:
1)Ephermeral Stream: desert/semi desert. Irregular flow in short episodes
2) Intermittent Streams: wet/dry seasons with relaible patterns
3) Perennial Streams: sustains base flow with source in wet area.

Coping with different rainfall patterns: different strategies

1) Storage
- store of water or food - underground river tapping

2) Migration/Evacuation
- Leave areas fir period when rain stops

3) Technology strategy
- transport water from ekse where

Management Case Studies:

Equitorial Climate:
*Hunters and Gatherers
* Slash and Burn

Savanna
*The Maasai
- water obtained from springs fed by snowmelt from Kilimajaro
- water sources are seasonal
- major droughts occur as deficit is present in water budget
- tribes move seasonally

Semi Desert
*Burkina Faso
- threat of droughts or famine
- rainfall confined to 2 months
- length and total rainfall unreliable

*North Kenya
- rainfall too low and unreliable to support settled agriculture
- Rain in heavy localised downpours
- Tribes migrate to new grass growth after downpour

Mediterranean
*The Nile
- Annual Flooding
- Summers dry but too hot
- Labour intensive
- Aswan Damn built to allow control of water
- Technology strategy/Storage
- no annual deposition of fertile silt by flood water so fertislisers needed.

Geography [[Weather and Climate]] 4.2

[[4.2: The relationship between Climate and Seasonality]]

Ecosystems: natural units in which the life styles and cycles of plants and animals are linkedto each other and to the non-living constituents of the environment to form natural living systems.

Natural Vegetation (Climax Community): Vegetation which will develop which is dominiated by plants which, of all those avaliable can
compete most successfully in the exsisting physical environment.
Biomes: Large global ecosystems relted to major climate zones.

The world Biomes:

* Tundra *Temperate Grassland *Tropical Rainforest *Taiga *Evergreen woodland *Savanna *Temperate deciduous forest *Desert


Adaptions of vegetation to Climate


- In sufficient rainfall, trees dominate
- the higher the rainfall and temperature the taller the tees and the larger the leaves
- higher the rainfall and the temperature the higher the rate at which plants produce organic matter
- in low or seasonal rainfall, plants develop xerophytic features
*Reduced leaf areas
*Sunken Stomata
*Long root system
*Slow growth rate
*Fire resistant trunks and seds
*Root storage system
- In seasonal climates, plants loose their leaves.

Geography [[Weather and Climate]] 4.2

[[4.2 Why seasonal climates and how does the effect vegetation?]]

The Climates:

Mediterranian

Hot Desert

Savanna

Equitorial Climate

Mediterranian:

July= subtropical high pressure leading to hot and dry climate

December = Polar Low Pressure leaidng to warm and wet climate

Hot Desert

July = Subtropical high pressure leading to hot and dry climate

December = Subtropical high pressure leading to hot and dry climate

Savanna

July = Equitorial LowPressure leading to hot and wet climate

December = Subtropical high pressure leading to hot and dry climate

Equitorial Climate

July = Equitorial LowPressure leading to hot and wet climate

December = Equitorial LowPressure leading to hot and wet climate

[[Water Budget Diagrams]]

A: Water Surplus

-Precipitation is greater thanpotential evapotranspiration

- Soil Water store is full

B: Soil Water Utilisation

- p.EVT greater than precipitation

- water store used up by plants

D: Soil Moisture Deficiency

- Soil Moisture store used up

- precipitation absorbed: no run off

- river levels fall/dry up

E: Soil Moisture Recharge

- water stores start to fill

F: Field Capacity reached

- ground water stores used

Geography [[Weather and Climate]] 4.2

[[4.2 Why do seasonal variaty o f climates occur?]]

Equinox: 12 hours of daylight and 12 hours of darkness which occurs when the sun is directly above the equator.

Position of the Sun::

22nd December = Over Tropic of Capricorn = winter solstice

21st March = Over Equator = Vernal Equinox

21st June = Over Tropic of Cancer = Summer Solstice

23rd Spetmeber - Over Equator = Winter Equinox

The Tropicsheya: 231/3 N and 231/3 S

* Area inbetween the tropics of Cancer and Capricorn where at at least one occasion throughout the year the sun will be directly overhead.

* The closer the place to the tropic of cancer or capricorn, the closer together the times the sun is overhead.

- As the sun moved north, so do the pressure belts as they are due to the suns heating of the air

- sun moves through 47 degrees of latitude each year

Pressure belts move 5 degrees north and south of their central locations.

In June, the pressure belts have moved north

In December, the pressure belts have moved south

- The weather systems move with the pressure belts.

Geography [[Weather and Climate]] 4.2

[[4.2 Why do seasonal variations of climate occur?]]

The theoretical model of air rotation based on a non-rotating earth:

The actual model of air rotation on a rotating earth:

The ITCZ at the equator:

Pressure, Rainfall and frontal zones:

Tri-cellular Model of Air movement:

Geography [[Weather and Climate]] 4.2

[[4.2 Why do seasonal variations of climate occur?]]

Coriolis force = the effect that the rotationm of the earth has on any moving body.

*Northen Heisphere - air is deflected to the right by the coriolis force

*Southern hemisphere - air is deflected to the left by the coriolis force

*Where the winds meet at the equator they are rising, due to heat and spiral effect

* Air sinks and some heads back to the poles and some heads to equator

Front = the meeting of two types of air. Eg, the meeting of the warm tropical air and the cold polar air at the polar front. Here, the warm air rises up over the cold air.

Convergence = two lots of air coming together and rising leading to low pressure

Divergence = two lots of air meeting and sinking leading to high pressure.

Intertropical Convergence Zone (ITCZ): area of converging air at the equator

Antucyclones = areas of high pressures

Low Pressure formed by sinking air gives wet weather and leads to depressions

High pressure formed by rising air gives dry weather and leads to anticyclones

* Pressure belts are effected by the distribution of land and sea due to the ability of land/sea to warm up/cool down