5.1 introduction to soil systems Flashcards
how is soil a system and an ecosystem
system - inputs, flows, stores and outputs
ecosystem - has a living component
how is soil dynamic?
it is changing all the time:
- when wind blows it may be blown away
- water washes out nutrients - organic matter puts them back in again
etc.
what is the best soil for agricultures - what is it made of
loam
- more or less even mix of sand, silt and clay
different types of weathering
- physical weathering (breaking rocks down into smaller particle)
- chemical weathering
- biological weathering
what is soil made up of?
minerals, organic matter, air and water
what are soil’s four primary functions?
- medium for plant growth (supplies nutrients and water)
- major water storage and purification system
- provides a habitat for organisms
- modifies the atmosphere through respiration of the soil organisms and plant roots
what factors affect the characteristics of soil?
- climate
- organisms
- parent material
- time
how can climate effect soil characteristics?
precipitation/evaporation balance which determines the dominant direction of water movement
how can organisms effect soil characteristics?
soil organisms break down the dead organic matter and mix it into the upper layers of the soil
how can time effect soil characteristics?
the development of soil is a long and slow process - so it is considered a non-renewable natural capital - different stages of formation of soil can lead to different characteristics
definition of ecosystem
Ecosystem is a community of interdependent organisms and the physical environment they interact with. A community is a group of populations living and interacting with each other in a common habitat.
how is soil an ecosystem?
qualities that ecosystem and soil share:
- biotic factors interacting with abiotic factors
- biodiversity
- system: inputs, outputs, stores, flows
- transfers and transformations
- open system (energy and matter are exchanged)
- many species
- food web
what are some biotic elements of soil?
- mico-organisms (bacteria, algae and fungi)
- macro-organisms (earthworms, insects, mites, mammals etc.)
how do decomposers contribute to soil?
it creates plant nutrients and microbial remains - this binds the soil and gives it its crumb structure
what are inputs of soil?
- minerals
- organic matter
- gases
- water
elaborate on minerals as an input of soil
- comes from weathering of the parent material
- weathering: through physical, chemical and biological processes
elaborate on organic matter as an input of soil
- living organisms that are on and in the soil
- during succession early plants die - add organic material to the soil
- they add organic material to the soil and carry out some of the soil forming processes
elaborate on gases as an input of soil
- certain plants fix atmospheric nitrogen and change it into nitrates
- nitrogen fixation - forms an input into the soil system
- oxygen is removed and carbon dioxide is added to the soil
elaborate on water as an input of soil
precipitation
what are stores of soil
- organic matter
- organisms
- minerals
- air
- water
- nutrients
elaborate on organic matter as a store of soil
DOM - dead organic matter
- anything that once lived in an ecosystem becomes the organic matter store in the soil
- a store of nutrients that can be taken up by the plants to be used for growth
elaborate on organisms as a store of soil
- organisms add nutrients to soil when they deposit waste
- remove oxygen and add carbon dioxide to break down dead organic matter
what are the outputs of soil
- organic matter
- water
(water leaches minerals from soil) - gases
- wind physically removing soil by blowing it away
what are some processes, transfers and transformations?
- leaching and evaporation
(dry places - evaporation levels are high)
(leaching - nutrients are leached out of soil) - decomposition
(break down dead organic matter - release the plant nutrients) - weathering
(breakdown of parent material adds minerals to the soil)
