Unit 5: Soil Systems & Society Flashcards
What are four reasons why soil is important?
- All of the food we consume depends on soil
- Soil is a habitat for many organisms
- Soil stores both water and nutrients for ecosystems
- Soil filters the water that passes through it and alters its chemistry
How long can the formation of 1 cm of soil take to renew?
15-100 years (depending on climate)
pedosphere
soil sphere; a thin bridge between the biosphere and lithosphere
How is soil produced?
soil is produced by the weathering of rock, deposition of sediments, and decomposition of organic matter
How long does it take for soil to be produced?
200-1000 years
What are the four main components of soil?
- mineral particles from underlying rock
- organic remains that have come from plants and animals
- water within the spaces between the grain
- air within the spaces between the grain
What is the soil ratio of solids to pore spaces?
Soil is typically a 50:50 mixture of solids and pore space
What is the function of air in soil?
provides oxygen for organisms and plant roots
What are the 4 functions of water in soil?
- allows dissolved mineral salts to be available to plants
- rapid downward movement of water causes leaching
- rapid upward movement causes salinization
- large volumes of water in the soil can cause water logging leading to anoxic conditions and acidification
leaching
minerals dissolved in water move through soil
What is a function of rock particles in soil?
provides the skeleton of the soil
What are the 3 functions of humus in soil?
- gives the soil a dark color
- as it breaks down, it returns mineral nutrients back to the soil
- absorbs and holds on to a large amount of water
What are the 2 functions of soil organisms in soil?
- decompose dead organic matter
- larger soil animals help to mix and aerate soil
What kinds of organisms reside in soil?
soil invertebrates, microorganisms, and large animals
What are two kinds of rock particles?
insoluble and soluble
What are examples of insoluble rock particles?
gravel, sand, silt, clay, and chalk
What are examples of soluble rock particles?
mineral salts, compounds of nitrogen, phosphorus, potassium, sulphur, magnesium, etc.
humus
partially decomposed bodies of dead plants and animals
What elements make up the air in soil?
mainly nitrogen and oxygen
From where does water enter soil?
water either seeps down from precipitation or moving up from underground sources by capillary action
soil horizons
separate zones (horizontal layers) within soil
soil profile
cross-section view of soil
O Horizon
surface litter
A Horizon
top soil