Chap 7 : Soil Aeration and Temperature
Key Terms:
Hydrophytes : plant species that have adapted to
waterlogged soils (ex:// rice)
Aerenchyma: tissue within plants that transport
oxygen to roots in situations of waterlogged soils
Mass flow: exchange of O2 into the soil. Influenced
by soil moisture, wind, and fluctuations in
barometric pressure
Diffusion: molecules moving from high concentration
to low concentration, which for soils is the transfer
of CO2 into the atmosphere and O2 into the soil
(Refer to Fig 7.3)
Anaerobic: absence of O2
Redox Potential: measured in volts or millivolts.
Occurs when a substance acquires or loses an
electron
Core cultivation: process to enhance soil aeration.
Remove core like structures from the surface
horizon to allow the gas exchange
Wetlands: soil saturated with moisture (seasonal or
year round)
Wetland delineation: finding the dry boundaries of
wetlands on the ground/ wetland mitigation
_
~ O2 is a strong oxidizing agent
Hydroperiod: the amount of time a wetland has
presence of surface water (seasonal wetland)
Hydric Soil: soils that begin to affect the growth of
plants due to the amount of saturation within them
Hydrophytic Vegetation: plants capable of living in
saturated soils and anaerobic conditions
Wetland Mitigation: creation/restoration of new/old
wetlands
Soil Solarization: controlled heating process, which
involves covering an area with plastic. The purpose
for this is to raise the surface soil temp to approx 5060 degrees C which helps to minimize weeds, pests,
etc
Frost Heaving: when soil thaws and then freezes
particles within the soil begin to rise (ex://rocks,
posts, rooted plants)
Albedo: reflected radiation from the land surface
Aspect: the direction a slope is facing (N,S,E,W)
Specific Heat: (heat capacity) heat characterized per
unit mass
Thermal conductivity: ability of a material to conduct
heat (influenced by moisture content and
compaction)
Important Points About The Chapter
~ Pore sizes alter H2O
~ Dry soils heat more
~ Interchange of CO2 and O2 is
percolation
quickly than wet soils
constant btw soil and
atmosphere
~ Well oxidized soils are
coloured red, yellow, and
reddish brown
~ CH4 and H2S are formed when OM
~ Tillage can cause macroporosity (as a
decomposes
long term effect)
~ H2O logged pores prevent diffusion of O2
~ Macropore space decreases the deeper
you move down a soil profile
~ Ethylene (C2H4) is toxic for plant roots
(occur when exchanges of gases btw
atmosphere and soil are too slow)
~ CO2 is very concentrated in soils
and can be toxic to plant processes
~ Warmer temp’s can cause depletion of
O2 and release abundant CO2
~ Excess moisture causes soil
to become waterlogged
Soil Aeration and Temperature
~ Plants are more affected by soil
~ Insufficient O2 can cause soils to
temp then surface air temp
have shades of gray and blue
~ Solar Radiation is the primary source of
~ Tree/potted plants require sufficient O2
reaching the roots
~ Microbial occurs most frequently at
warmer temperatures, such that areas of
slightly cooler temperature may perform
heating processes on crops
heating soil. Depending on where the soil
is located (slope aspect, under thick OM)
can all alter how much this radiation can
heat the soil
~ Hydric soils are defined by
periods of saturation, reduced
conditions, and hydric soil indicators
~ Soil temp can affect
productivity of vegetation (seed
germination and root functions)
~ Freeze/thaw can uproot plants,
posts, can cause roads to shift or crack
due to the expansion and compression
of the soil beneath during these F/T
processes.
~ Forest fires can heat soil temp fast
~ Mulch: can alter soil temp.
~ It is important for soil to be ventilated
but prevent H2O infiltration for
extended periods of time
Mulch is a natural erosion
controller of soil. Plastic mulch can
heat up soil temp
to allow for proper exchanges of gases
Geog 3080: Soils Chap. 7 Review By: Erin Y