#14 Decomposition, Nutrient Cycling, & Biogeochemical Cycles Flashcards
what is nutrient cycling?
the transformation of organic nutrients into mineral form and back into organisms through decomposition and mineralization
Define decompositon
the breakdown of chemical bonds in organic molecules, resulting in energy, carbon dioxide, and water.
which 4 processes make up decomposition
- leaching
- fragmentation
- structure changes (physical and chemical)
- ingestion/excretion
Decomposers are categorized based on ______?
size and function
______ are used to examine the decomposition of plant litter
litter bags
how are litter bags used by ecologists
a fixed amount of litter is put into the bags. The mass of litter remaining decreases continuously as time progresses and the rate of decomposition is related to the litter quality.
How do these carbon forms affect the decomposition rates:
- glucose and other simple sugars
- Cellulose and hemicellulose
- lignin (and others)
- glucose and other simple sugars: small, high quality sources of carbon, high-energy bonds.
- Cellulose and hemicellulose: structurally complex, more energy required to break bonds, moderate quality
- lignin (and others): very large and complex molecules, slow to decompose, low quality
what is the only group that can decompose lignin?
Basidiomycetes
For the following, what is their % carbon and how long does it take to break down?
- Proteins, simple sugars, soluble compounds
- Cellulose and hemicellulose
- Lignins
Proteins, simple sugars, soluble compounds: 15% carbon - decompose very quickly and non remaining in a few days
Cellulose and hemicellulose: 60% carbon - decomposed more slowly and were completely broken down in three weeks
Lignins: 20% carbon - the majority remained intact by day 80
the rate of organic decay is related to what three things?
- plant litter quality
- soil properties (texture and pH)
- climate (temperature and precipitation).
net mineralization rate
the difference between the rates of mineralization and immobilization.
NMR = mineralization rate - immobillization rate
mineralization
the transformation of nutrients contained in organic compounds into inorganic forms
- minerals in the soil to usable inorganic forms
Immobilization
the uptake and assimilation of minerals by microbial decomposers
(immobilizing and digesting the nutrients)
How is nitrogen released into the soil with respect to litter breakdown and mineralization/ immobilization
- Nitrogen starts at 100
- Nitrogen decreases as water soluble compounds are leached from the litter
- Nitrogen increases as decomposers immobilize nitrogen from outside the litter.
- The mineralization rate exceeds the immobilization rate and nitrogen is released into the soil
what is the (bio)geochemical cycle
the cyclic flow of nutrients from the nonliving to the living and back to nonliving components