BISC201 - Exam 2 Decomposition

Decomposition: breakdown of organic matter into simpler, non-organic forms and energy

Litter bags, calculating decomposition constant

  • dM/dt = -kM

    • M= current mass

    • k = decomposition constant → higher k = faster decomposition

    • dM/dt = change in mass over time

How temperature/precipitation affect decomposition rate

  • Overall rates of decomposition increase with temperature and precipitation, variation between habitats and species

Decomposition on land and in water

  • Fast-moving water speeds up decomposition through physical breakdown of litter

  • Still water slows decomposition, colder, and less oxygen

  • Decomposition of fallen leaf material is an important source of productivity for aquatic systems

Aerobic decomposition

  • Organic compounds converted to energy and CO2 in the presence of oxygen through oxidation

  • Same basic process as respiration, just using dead material

  • More efficient than anaerobic, more energy produced, faster

3 steps of anerobic decomposition

  • More complex, produces CO2 and methane, less efficient, less energy produced, slower

  • 1) hydrolysis: water breaks down larger molecules (carbohydrates, protein) into simpler molecules (simple sugars, Amino acids)

  • 2) fermentation: creates alcohol, simple organic acids (Carboxylic acid, carbonic acid) and releases CO2

  • 3) methanogenesis: alcohol/acids converted to CO2 and methane

C:N ratios in leaf litter

  • Lignins, tannins, phenolics, and cellulose in leaves

  • Nitrogen limiting nutrient in leaf litter

  • Too little nitrogen slows decomposition

  • Lower C:N ratio = higher palatability

  • High amounts of lignin, cellulose = low palatability

Succession in leaf litter

  • 1) large arthropods (beetle, larva, ants, isopods, millipedes)

  • 2) small arthropods (mites, springtails)

  • 3) fungi and bacteria

Decomposers: can be classified by size, body size limits, what size fragments they can consume

  • Epiedaphic: soil surface

  • Eudaphic: deep soil

  • Hemiedaphic: both

Succession of insects on decomposing animals

  • 1) blow flies, flesh flies, house flies

  • 2) Scavenger flies, rove beetles

  • 3) Burying beetles

  • 4) Predatory beetles (feeding on larva)

  • 5) Fungi, dermestid beetles