Terrestrial environments Flashcards
Lecture 3
What is dessication?
maintians water balance and minimizes water loss
- waxy plant cuticle.
- dry skin, arthropods, reptiles, mammals, birds
- habitat preferences of soft bodies invertabrates
drink/ eat water / take up water from roots
What is the effect of gravitational forces?
need structural materials to remain erect
- internal skeletons in animals (size limitations)
- cellulose for plants
Why are terrestrial conditions more variable that aquatic environments?
Temperature (Kalahari Summer 20-45degrees winter <0)
Rainfall
- organisms need to cope with a wide range of conditions.
Why does plant cover influence the vertical distribution of light?
The amount of light available is relative if there is a shadow or. cave, air itself doenst influence light in the same way that water does.
amount of light reflected and absorbed by leaves in different levels of canopy depends on SA (surface area -leaf size and shape) and leaf orientation (angle of leaves relative to the sun)
affects how much light reaches the ground.
What is PAR?
checkout graph in slides
photosynthetic available radiation - available light available for photosysthesis to occur.
what are plant adaptions found on forest floor?
They are evergreen or adapted for less light.
Characteristics of soil?
*Medium for plant growth
*site of decomposition
*provides habitats for many organisms
*controls the fate of water
soil is a three dimensional unit - unconsolidated, crumbed rock resting on a base of hard unweathered rock.
How does soil form?
Processes
results form the breaking down of parent rock (consolidated rock)
Mechanical weathering - water (ice wedging, abrasion), temp, wind, organisms (plant root growth) - breaks rock into smaller pieces but doesnt chemically change its composition.
Chemical composition - dead organisms, soil organisms, water & oxygen (water can dissolve rock. O2 reacts with Fe forming FeO which changes the colour and texture of rock) - changes the chemical composition of the rock breaks rocks and forms minerals.
What is parent material?
Influencing soil forming
Underlying bedrock
Glacial deposits
Imported Material
* wind: sand/silt
* gravity: down slopes
*flowing rivers
What are biotic factors?
Influencing soil forming
plants transfer light energy into carbon and transported into soil
*roots dig and burrow, bring nutrients to surface, breaks parent material, stabilises soil.
Animals burrow and dig
Fungi and bacteria decompose organisms.
How does climate influence soil forming factors?
Temp affects rates of biochemical reactions
amount of rain directly influence mechanical breakdown and indirectly impacted by plants
How does typography influence soil forming factors?
How does time influence soil forming factors?
takes a long time for good soil to develop but very easy to quickly drain it of nutrients.
What does soil depth depend on?
- slope
- weathering / breaking down parent rock
- parent rock / material
- vegetation
Where are deep soils found?
Grassland
bottom of slopes
alluvial plains (flood plains)
What is soil texture made up of?
Sand - largest soil particles
Clay - smallest component
Silt - middle sized soil particles.
Pore space
- the movement of air and water in and through the soil
- penetration of roots and plants
Grain size influences how well soil holds onto water.
be able to interpret the triangle graph
What is the moisture holding capacity of soil?
Saturation - all spaces and to excess water is in soil
Field capacity (FC) - when water fills all the pore spaces and are held to each soil grain by capillary action - works against gravity.
Wilting point (WP) - when plants can no longer extract water from the soil.
Available water capacity (AWC) - FC - WP
water that the plant uses.
NB graph
Silty clay - has very high water retention
Loam - available water capacity is the highest
Sand - low water rention due to small surface area
Consider the specific impact of human activity on the characterisitcs of soil
pesticides kills soil invertabrates increasin gthe compaction of soil
consider the potential direct consequneces of human impact on soil chracteristics.
reduces water penetrating soil.
