Lecture 2: Soil habitat Flashcards
Soil formation (Dokuchaev equation)
soil=f(cl,o,r,p,t,…)tr
climate, organisms, parent material, relief, relative time
What is pedogenesis
exposed rock formes soil
what is weathering
degradation of material by chemical/physical processes accelerated by orgniams
newly developed soil layer
lithosol/entisol/rudisol
Over time formation of forst soil
colonisation of thin litter layer by lichens, mosses, liverworts
lithosol formed with shrubs increasing litter layer and weathering
deciduous forests alter parent material
rock cycle
magma forms igneous rock through crystallisation
exposed to weathering
form sedimentary rocks via erosion
heat and pressure make metamorphic rocks
igenous rocks
granite, basalt, gabbro
sedimentary rocks
limestone, sandstone, shale
metamorphic rocks
marble, slate, quartzite
weathering rind
biological processes occurring here with mycorrhizae helping
Soil horizons
litter
organic (O)
surface (A)
subsoil (B)
substratum (C)
bedrock (R)
what is O horizon
organic material with lots of humus
what is A horizon
OM accumulates and leaches
what is B horizon
deposited minerals and metal salts with less OM
what is C horizon
partly weathered parent material
what is R horizon
un-weathered parent material
soil composition
mostly mineral matter
water
air
less than 5% OM
mineral basis of soils
clay (smallest particles)
silt
sand
gravel (largest particles)
soil textural classes
form a triangle of clay, silt, sand %
why is soil texture important
helps define suitability for agriculture
what is clay-rich soil good for
water and nutrient retention
what are sandy soils good for
drainage
what are heavy soils
how hard to get plough through
insulators
minerals
solid chemical compounds
primary rock minerals
silicates
valency
fill up from outside shells
2,8,8 shells
hydrogen bonds
covalent hydrogen atoms bind to electronegative atoms
quite strong
silicates
silicon tetrahedrons
what type of silicates do soils have
phyllosilicates
what are phyllosilicates
2D mineral sheets of tetrahedrons/octrahedrons
3D covalently bonded combos of layers
sheet
combinations of planes of atoms (silica in tetrahedral sheet)
layer
combinations of sheets (MICA, two silica sheets and alumina sheet)
crystal
stacks of layers
interlayer space importance
fillied with ions, water, etc. and determines soil properties
kaolinite crystal
little interlayer space so little water in
muscovite crystal
covalent sandwich bonds
potassium ions weak bonds
can split sandwiches easily
chlorite crystal
strong bonds
low interlayer space
