BIOM-360 Lecture Notes - Lecture 8: Sapric, Lignin, Humus
2 May 2018
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Nutrient Cycling
Element re-use is the base for a living planet.
Carbon Cycle
C sources (C release): respiration
Microbial decomposition, industry.
C sinks (consume C): photosynthesis
Plants, bacteria, protists, chemolithoautotrophs.
C reservoirs: rocks, oceans, oil, plants, humus (dead matter waiting to be decomposed)... accounts for
more C than living organisms.
For organic matter to accumulate, photosynthesis has to exceed respiration.
Organic compounds are degraded to CO2 and CH4.
Both are potent greenhouse gases so their accumulation leads to rises in temperature.
Degradation of Organic Matter
Influenced by presence of nutrients in environment (O2) and presence of appropriate microbial
communities.
Mineralization → decomposition of organic matter to simpler inorganic compounds (CO2, NH4), making
them available.
Soil → the product of decomposition, a very slow process.
Lignin Degradation
Lignin → complex organic molecule in plant cell walls.
Degrades under oxic conditions (bacteria and decomposing fungi).
WIthout anything to decompose, lignin accumulates to form peat bogs and muck soils.
Document Summary
Element re-use is the base for a living planet. C reservoirs : rocks, oceans, oil, plants, humus (dead matter waiting to be decomposed) accounts for more c than living organisms. For organic matter to accumulate, photosynthesis has to exceed respiration. Organic compounds are degraded to co 2 and ch 4 . Both are potent greenhouse gases so their accumulation leads to rises in temperature. Influenced by presence of nutrients in environment (o 2 ) and presence of appropriate microbial communities. Mineralization decomposition of organic matter to simpler inorganic compounds (co 2 , nh 4 ), making them available. Soil the product of decomposition, a very slow process. Lignin complex organic molecule in plant cell walls. Degrades under oxic conditions (bacteria and decomposing fungi). Without anything to decompose, lignin accumulates to form peat bogs and muck soils. All naturally produced organic n is of microbial origin.
