Topic 4 Flashcards
Organisms on the land deal with significant losses of water due to ..
evaporation
Living cells contain..
75-95% water
Air has low..
density/viscosity relative to water (large gravitational forces)
How organisms survive gravitational forces
- cellulose/lignin reinforcing plants
- skeletons in animals
Foundation of all terrestrial life
SOIL
Soil
natural product formed by the weathering of rocks and the actions of living organisms
Soil controls
date of water in terrestrial ecosystems, break down waste products, release nutrients and habitat for organisms
Maintaining water balance is major driver of
evolution
What causes variation in the moisture-holding capacity of soil
- climate
- type of parent material
- topography
- aspect
- presence/absence and type of vegetation
Climate
directly influences the physical/chemical reactions in soil and water availability
Physical and chemical characteristics determine the..
properties of the soil
Texture is used to..
differentiate soil particle sizes
Sizes of soil
- gravel (2.0 mm)
- sand (.05 - 2.0mm)
- silt (.002 - .05 mm)
- clay (
Soils texture is a % of
sand, silt and clay components divided into texture classes
Soil texture determines
- soil fertility
- size of soil pore spaces
Large soil pores cause
rapid water infiltration, percolation, doing but have low holding capacity
Small soil pores cause
slow water infiltration, percolation and drainage but the soil does have higher holding capacity
Topography
slopped surface is less likely to hold moisture than flat ground due to gravity
Windward slopes receive
more precipitation
Vegetation alters
- light
- temp
- moisture
- wind movement
- structure
What is the dominant factor for terrestrial environments
absorption and reflection of light by plants
Amount of light at any depth in the canopy is affected by
the amount of leaf material above it
Quantity of light at varying heights can influence..
plant species composition, growth rate and interactions
Leaf area index (LAI)
measure often used to quantify the impact of leaf quantity on available light
Soil depth determined by
degree of weathering, type of parent materials, vegetation
Grasslands tend to have..
deep soils. low decomposition rate and large amounts of organic materials being added from roots underground
Forest tend to have..
thin soils. high decomposition rate and organic material added to surface
Soils which develop on slopes tend to be
shallow while those in plains tend to be deep
Initially soil development occurs within the
parent material
Over time the soil changes from the ..
surface down through the accumulation of organic material
Layers
termed horizons. collectively called the soil profile
O horizon
organic layer, made up of debris in various stages of decomposition
A horizon
called topsoil and composed of bother mineral and organic material
B horizon
called subsoil and contains less organic and more mineral components relative to the A
C horizon
layer of unconsolidated material and generally made of same material which the soil developed
