Soils : Soil formation

the five primary formation factors of soil

-climate(cl)

- organisms(o)

- relief(r)

- parent material(p)

- time(t)

parent material

- all materials, both weathered and unweathered, from which the soil formed

lithosequence

soils that differ primarily as a result of parent material as a soil-forming factor.

Alluvium

material deposited by a stream

Till

The sediments deposited directly by a glacier (clay to boulders)

- unstratified and unsorted

outwash

material deposited by meltwater from a glacier

- well.sorted and stratified

Eolian Deposits

wind-deposited soil material, mostly silt and fine sand (dust)

lust

wind blown silt

aerosolic dust

-A type of eolian material that is very fine (about 1 to 10 micrometers)

-Finer than most loess.( not thick)

- contribute substantial amount of CaCo3 to the US west

dividing line between silt and clay

*425 micrometers

*20 micrometers

organisms function in soil

the summation of plant disseminules reaching the soil site or the potential vegetation, it is approximated by a list of species growing in the surrounding region that could gain access to the site

soil organisms soil formation factor

- influence aeration, acidity, temperatures, moist/dry conditions, nutrients

ecosystem engineers

- alt. of physical env.

- burrowing animals=huge macropore

- soil inversion(ants, earthworms), stir up soil

- dung beetles= enhance nutrient cycling

Earthworms

- most imp. macro fauna in soil

- enhance decomposition

- stimulate microbe activity

- nutrient cycling

- inorganic to unstable nutrients

-mix soil

Topography (relief)

-change in elevation

aspect

- which way slope faces

- can give you a microclimate

---> vegetation impact

- hemisphere specific

Influence of aspect greatest at

40-60 degrees latitude; not by equator

warmest

S, W slope

coldest

NE slope

processes influenced by soil temp.

- water availability( frozen)

- heat availbitily

flat line area

-vertical horizonation

-thicker soils

-residual

slope

- thinner soils

- shallow

bottom of slope

thick, lots of transported material, potential to have more horiznation

convex

curved outward

concave

curving inward

climate

the regional climate= mean annual precipitation and mean annual temp.

soil moisture influences

- precipitation

-form of precipitation

- seasonal variability

- transpiration and evaporationrate

- slope

- aspect

-depth of soil profile

- texture

high evaporation and high plant use

nothing gets into soil

low evaporation and low plant use

more rainfall

soil temp influences

- lat/altitude

- absorption& reflection of incoming solar radiation

- elevation

- seasonality

- cloud cover

- air pollution

- soil color, veg cover, aspect

Time

is the only thing that can't be controlled

young soil

any numerical age, bad horizonation

mature soil

good horizonation; any numerical value

climates with young soil that is old

cold and dry

climates with mature soil that is young in age

rainforest( warm and wet)

humans influence on soil

-changes to soil class, texture, etc.

-human-made soil horizons( plowing)

-new parent material

-dep. soil disturbance

- top soil changes( erosion)