APBI 200 Final

Regosol order diagnostic process horizon

• no B horizon (Ah straight to C) and can have repeating Ah/C/Ah layers

• weak soil development

• young soils that occur in every ecozone but are rarely dominaant

• found in areas with unstable land

Brunisol order diagnostic process and horizon

• leaching, formation of iron and alumnium

• modified b horizon (Bm, Bfj, and Btj)

• more developed than regosols but not fully mature

Luvisol order diagnostic process and horizon

• clay accumulation in B horizon (Bt). very big difference in texture between A and B because of this.

• deciduous and mixed boreal forests or in forest-grassland transition zones for mild-cold areas

Chernozem order diagnostic process and horizon

• limited leaching and more accumulation of organic matter in the topsoil (Ah greater than 10cm)

• grassland vegetation and continental climates

Solonetz order diagnostic process and horizon

• sodium salt accumulation in B (Bn and Bnt)

• grass or grass-forest cover

• saline parent materials

• same ecosystem as chernozems but they are much higher in Na content

Podzol order diagnostic process and horizon

• Fe and Al accumulation in B (Bf, Bhf, Bh) orange colour

• found in the canadian shield and in areas with high precipitation. often in coniferous forest vegetation.

Gleysol order diagnostic process and horizon

• reducing anaerobic conditions due to fluctuating water table in B, aka surface water accumulates. (Bg)

• reduction of iron and other metals which changes soil colour to greyish

Organic order diagnostic process and horizon

• organic mater at least 40cm thick or 60cm for Of (Of, Om, Oh)

• found in forests and wetlands, or in areas with leaf litter accumulation

Cryosol order diagnostic process and horizon

• Presence of permafrost within 1-2m of the surface (Bz/y or Cz/y)

• found in northern canada

Vertisol order diagnostic process and horizon

• cracking and mass movement of materials due to shrink/swell of clays during wetting/drying cycles (Bss or Css or Bv or Cv)

size of macro organisms

>2mm organisms

size of meso organisms

0.2-2mm organisms

size of micro organisms

<0.2mm organisms

heterotrophs

organisms that use organic compounds as a source of energy and carbon

autotrophs

organisms that get carbon from CO2 and energy from photosynthesis or oxidation of various elements/compounds

litterfall

dead leaves/branches/twigs that fall and add organic matter and nutrients to soils

roots

consume oxygen, water, nutrients. release co2 and organic substances. once dead they return organic matter and nutrients to the soil

earthworms

burrowers of soil that mix and aerate the upper soil horizons. fecal casts contribute to development of granular aggregates

nematodes (threadworms)

parasitic organisms that feed on bacteria and excrete excess nitrogen as inorganic N. this increases net mineralization.

mites

help litter decompose. some are predators. used as biological control agents

collembola

mesofauna that are fungal grazers and help with decomposition of soft organic residues.

millipedes

help with decomposition and litter shredding

centipedes

mostly predators, some eat decaying plant material

algae

autotrophic and abundant in wet soils near surface (b/c they need light for photosynthesis). produce lots of SOM and help with the formation of soil aggregates.

protozoa

feed of bacteria, fungi, or fragmented organic litter. enhance N cycling by eating bacteria and releasing N into soil. control disease in soil by regulating bacteria and fungi populations. food source for other soil organisms.

fungi

heterotrophic aerobic organisms. important in decomposition of organic compounds. form symbiotic associations (mycorrhizae) with plants. can act as plant pathogens. major role in forming humus and in aggregate stabilization.

hyphae

threadlike fillaments in fungi

mycelium

a network of hyphae

bacteria

important in the decomposition of dead organic matter and mineralization of nutrients like N and S to forms available to plants.

actinobacteria

filamentous bacteria that decompose SOM and can sometimes fix atmospheric N.

cyanobacteria

have chlorophyll and do photosynthesis. many can fix N and form symbiotic associations with algae and protozoa.

archaea

important in C and N cycling

rhizosphere

zone around the roots where soil microorganisms are concentrated

sources of soil N

• biological fixation

• deposition through precipitation

• addition of organic matter

• synthetic fertilizer

losses of soil N

• leaching

• plant harvesting

• gasseous losses (volatilization and denitrification)

• erosion (wind and water)

Transformation processes of N

• mineralization/immobilization

• ammonium fixation

sources of soil S

• organic residues

• fertilizers

• throughfall and absorbtion

losses of soil S

• harvesting

• erosion

• leaching

• volatilization

• coal/oil burning

transformations of S

• mineralization/immobilization

• redox

sources of P

• organic residues

• fertilizers

losses of P

• harvesting

• runoff

• erosion

transformations of P

• mineralization/immobilization

• desorption/adsorbtion

• mycorrhizal association

sources of K

• fertilizer

• organic residues

losses of K

• runoff

• erosion

• leaching

• harvesting

transformations of K

• throughfall

• leaching