AUENV 233 Lecture Notes - Lecture 2: Colloid, Silt, Sapric
30 May 2018
School
Course
Professor
Lec 2 Soil Science AUENV 233
[effective] Precipitation + temperature
Effective Precipitation
▪ Water is required for weathering – especially for every chemical weathering process
▪ Needs to enter profile
▪ ALSO need to percolate through soil
▪ The greater the depth of reach, the greater the depth of weathering
What are the implications for dry regions?
▪ Water evaporates, brings salt to the surface. → This would require irrigation.
Factors affecting Precipitation
a.) Seasonal distribution [of precip] – if precip spread out eel oer tie, does’t peetrate the
soil as deep as if it all comes down in one season.
b.) Temperature and evaporation – high evaporation and temperature stunts water from
penetrating deep. Or high plant use could prevent water going deep.
c.) Topography – slope could prevent absorption – could also make other regions more moist. Eg –
the bottom of a valley
d.) Permeability – sad [ater flos through], la [does’t let ater through]
Temperature
▪ More warm = more reactions/activity (the deeper the activity)
▪ For every 10 degree increase, reactions double → Q10
▪ Comparison across altitudes
▪ Temperature directly affect vegetation
Vegetation
Grassland
Forest
Higher turnover rate
Exists longer – more organic input
Eg – leaf litter
bacteria
Fungus instead to breakdown leaf litter and other inputs. This creates → E
layer (white layer)
▪ vegetation that grows in clumps – eg permafrost, dessert
o the roots extend outward around them trying to get all the nutrients and moisture they
can
o let’s the gro ad drop leaf litter right i the lup the’re groig
o creates more soil in the clump – clumps of nutrients
Organisms
Animals
find more resources at oneclass.com
find more resources at oneclass.com
▪ animals who biopederbate → insects are the most important, so many of them!
o Move material [nutrients] from the bottom horizons to the top
o Water can flow into burrows – more percolation
▪ Animals who aggregate soil
▪ Human effects
o Burning and clearing lands
o Removal of natural vegetation and tilling soil
o Adding water in arid regions
o Adding fertilizer to soils w low fertility
o Bulldozers are like glaciers? – reset soil formation process, down to bedrock
o Development of new soils – dredging into new soils
Relief
→Configuration of land surface
o Elevation
o Slope
o Aspect – direction the land [slope] is facing → amount of sun
▪ Less developed soils on south facing vs north facing
▪ Works with climate & vegetation
▪ Less developed on steep slopes
▪ Bottom of slopes depends on drainage & accumulation
▪ Salts – saliizatio at the otto of slopes…
Time
▪ Rates of weathering are SLOW – depedat o iteratios ad diff fators…
▪ oug or ature soils are ot liked to epliit ages
o dependant on horizons & formation – the deeper, the older/more developed
▪ resetting the clock = glaciation down to bed rock
How can you monitor the at different ages of the soil in one place [same climate, parents materials]?
▪ Alluvial plane – different terraces to monitor each level and each age of flood plain.
Processes of Soil Formation
1.) Transformations
▪ Chemical or physical modification of destruction & synthesis
▪ Involves weathering
o Eg – silicate clays, hydrous oxides of iron, organic matter
2.) Translocation
▪ Movement of materials laterally within a horizon or vertically from one horizon to another
o Eg – water movement (UP AND DOWN)
o Organic matter into A, B horizon
3.) Additions
▪ Inputs of material from outside sources
o Eg – plant leaves or roots
o Fertilizers
o Dust particles
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Effective precipitation: water is required for weathering especially for every chemical weathering process, needs to enter profile, also need to percolate through soil, the greater the depth of reach, the greater the depth of weathering. What are the implications for dry regions: water evaporates, brings salt to the surface. Seasonal distribution [of precip] if precip spread out e(cid:448)e(cid:374)l(cid:455) o(cid:448)er ti(cid:373)e, does(cid:374)"t pe(cid:374)etrate the soil as deep as if it all comes down in one season. b. ) Temperature and evaporation high evaporation and temperature stunts water from penetrating deep. Or high plant use could prevent water going deep. c. ) topography slope could prevent absorption could also make other regions more moist. Eg the bottom of a valley d. ) permeability sa(cid:374)d [(cid:449)ater flo(cid:449)s through], (cid:272)la(cid:455) [does(cid:374)"t let (cid:449)ater through] Temperature: more warm = more reactions/activity (the deeper the activity, for every 10 degree increase, reactions double q10, comparison across altitudes, temperature directly affect vegetation.
