GHG IMPORTANCE OF SOILS Flashcards
how much carbon do soils contain in Pg? how much additional carbon does permafrost contain?
1500-2400 PgC (Peta= 10^15)
permafrost contains an additional ~1700 PgC
how much carbon do vegetation, oil reserves and atmosphere contain?
- 450-650 PgC
- 173-264 PgC
- ~730 PgC
why are soils known as ‘nature’s recycling system’?
- they return biomass and nutrients to forms that can be used by the next “generation” of life
how do soils support the growth of higher plants?
- they provide a medium for plant roots
- and supply nutrients that are essential for plant biomass and metabolism
soils support the growth of … plants by providing a … for plant roots and supplying … that are essential for plant … and …
higher
medium
nutrients
biomass
metabolism
soil properties are often in large part responsible for the types, … and biomass of … and microorganisms in ecosystems, and … the number of … (humans too) that vegetation can …
diversity
vegetation
indirectly
animals
support
what services are provided by soil?
- microbes
- fungal hyphae/fungi
- nematodes
- mites
- springtails
soils are home to phenomenal … and biodiversity
biomass
what is humus? what is the A horizon?
carbon that has resisted degradation
- very slowly decomposed
- plant and microbial origin
- provides soil with its dark colour, especially in the A horizon
- A horizon is almost biologically active layer, with higher organic matter and nutrients
which layer of soil is the most biologically active layer?
the A horizon
what is cation exchange capacity critical for?
nutrient retention
Colloids are the … particles: of … (mineral) or humus (organic), chemically …
smallest
clay
active
Bioavailable … is often limiting for soil fertility
Phosphorus
What factors can differ between soils?
- nutrient abundance and balance
- type of clay; proportion of various sized particles (sand, silt)
- pH (acidity, alkalinity)
- toxic elements
- salinity
- microbes
what are the differences between upland soil and wetland soil?
upland soil= elevated, largely used for agriculture
wetland= low-lying, wet soil
what are the uptakes and effluxes of forest soils?
CO2 uptake and storage through photosynthesis & prim production minus decomposition/respiration
CH4 uptake by methane-oxidising soil bacteria
CO2 efflux through autotrophic respiration (leaf, shoot and roots)
CO2 efflux through heterotrophic respiration (primarily from litter and SOM decomposition)
N2O efflux through microbial nitrification and denitrification processes
large, old trees do not act simply as senescent … reservoirs, but actively … large amounts of carbon compared to … trees
carbon
fix
smaller
what fraction of total global soil carbon do peatlands hold, despite only covering 3% of the Earth’s surface?
1/3
how much % of all atmospheric CH4 do peatlands emit annually?
about 10%
- high water-table (when precipitation is ample) leads to anoxia, slow decomposition, but greater CH4 emissions
why does Sphagnum peat decompose slowly?
- it is flooded, which makes it anoxic/anaerobic
- it is acidic
- it is nutrient poor
explain physical degradation in terms of pasture.
compaction due to hoof traffic often associated with over-grazing
bare soils are vulnerable to … and … erosion (physical degradation and erosion section)
wind
water
what are the factors of chemical degradation?
- depletion of organic matter and nutrients (from vegetation loss)
- contamination with chemical pollutants
- salinization (in dry areas, esp with irrigation)
- desertification (only occurs in arid, semi-arid and dry sub-humid areas)
what is salinisation?
- poor water management
- too much water evaporates from the surface
- salts left behind
- toxic to plants
