decomposition Flashcards
what is decomp
the physical and chemical breakdown of detritus into CO2 and inorganic
nutrients through chemical alteration, leaching and fragmentation
what does decomp balance
balance between primary production and decomposition strongly
influences carbon and nutrient cycling (no cycle, if no recycling
through decomposers)
what happens if no decomp? ex?
Detritus accumulation, the lack of availability of nutrients that are readily available and the
depletion of atmospheric carbon dioxide
Massive accumulation of cattle dung because dung beetle was evolved to using native
marsupials.
what three processes does decomp involve?
- Leaching by water
- Fragmentation
- Chemical alterations
Describe leaching by water
Mineral ions and soluble materials transported through soil, away from
decomposing OM
- Most important early in decomposition
- Pulsing by solubilization of decomposition
describe fragmentation
Fragmentation – physically breaking own the matter
- Freeze and thaw cycles
- Wet and dry cycles
- Surface area and volume such that as you break it down OM, surface
are gets larger compared to volume thus changes how minerals react
with ions in soil
what is impacted by break down of OM/SA
Photosynthesis - lower surface area to volume more allocation to
biomass of photosynthetic structures
- breaking down OM into smaller matter through fragmentation
increases surface area to volume ratio
- Soil texture -
describe chemical alteration
Changes chemical composition of detritus
- Primarily from microbes (bacteria and fungi)
- Less usable (organic) à usable (inorganic) forms
- Mineralization – the conversion of carbon and nutrients from organic
to inorganic
microbes? what do they do?
bacteria (animal material) and fungi (plant material) = microbes
- Secrete enzymes specialized to the niche to breakdown litter macromolecules into inorganic
forms to contribute to gross mineralization
what accounts for most decomp in aerobic environments
fungi
describe fungi
Intolerant to low O2 (if water is saturated there isn’t room)
- Secrete enzymes that penetrate plant cuticles and cell walls (lignin, cellulose,
hemicellulose)
How do fungi differ from bacterial
- Differentiates from bacteria because they have hyphal networks – allows them to import
and transfer nutrient over long distances - Tolerant lower availability of nutrients in a place due to transportation,
- Adapted to processing ligand and cellulose which are hard molecules hard to
break down
describe bacteria
-Specialized on labile substrates (animals)
- Tolerate low oxygen
- Differentiates from fungi such that they can continue processes under waterlog
conditions and low oxygen (Example: extreme soil compaction)
role of protozoans
- Predators of bacteria
role of nematodes
Predators of bacteria, fungi and also root herbivores (invertebrates)
describe mesofauna- two common types?
Taxonomically diverse
- Most common:
a) Springtails (Collembola): small insects that feed on fungi
b) Mites (Acari): trophically diverse, consume decomposing litter, predators of bacteria and
fungi
describe macofauna
- Ecosystem engineers that alter soil physical properties (tunnels change the flow of water,
change interactions between organisms)
-Earthworms (temperate) or Termites (tropical)
role of macrofauna
Fragment liter
-Alter soil structure
-Mix OM into the soil
how is decomp rate calculated?
Decomposition = Lt = L0 * e-kt
L = litter loss
decomp calc example
Lt= 30
Loe = 40
30/40 = e- k (12)
Ln (0.75)/12 = -k
-Ln (0.75)/12 = k
= 2.3% reduction per week
what is k=? higher k means?
K = litterfall/litterpool/ decomp constant
Higher k = higher decomp
Lower littler pool , less OM on ground , decoop is being done fast
how IS DECOMP measured as
Mass loss in litterbags
- Carbon dioxide release
- Mass balance (physical mass decomposition
look at graph of litter loss
ok
how does spatial variation in decomp work - soil surface
most decomp = soil surface
- litter inputs concentrated
- greater temporal variation in temp and moisture and decomp rates
- principally by fungi (aerobic env)
