Chapter 22: Decomposition & Nutrient Cycling

 

A generalized model of nutrient cycling

 

 

Retranslocation or reabsorption nutrients.........

 

 

 

 

Decomposition.........

 

Decomposing organisms are categorized into groups based on size and function
Microflora: bacteria and fungi
Invertebrate detritivores
Microfauna and microflora
Mesofauna
Macrofauna
Megafauna

 

 

Bacteria are the dominant decomposers of dead

 animal matter

 

 

Fungi are the major decomposers of plant matter

 

 

 

 

 

 

Results of a litterbag experiment in central Virginia.

Looks at decomposition of fallen leaves.

 

 

 

 

Organic matter decomposes at different rates

 

 

 

The carbon form available affects the consumption (or decomposition) rates:
Glucose
Cellulose and hemicellulose
Lignin*

 

*Lignin:

     C9H10O2, C10H12O3, C11H14O4

 

 

 

An experiment that studied rate of carbon decay in straw found the following........

Variation in rates of decay of different classes of carbon compounds

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Nutrients in Organic Matter Are Mineralized During Decomposition

 

 

If the nitrogen content of the litter material is high, then mineralization may exceed the rate of immobilization from the onset of decomposition

 

 

 

 

 

Humus

 

 

Mulch vs. Compost vs. Humus

 

 

 

The rhizosphere