Chapter 21: Decomposition and Nutrient Cycling Flashcards
Pathway of an element or nutrient through the ecosystem, from assimilation by organisms to release by decomposition;
See also internal cycling
nutrient cycling
Breakdown of complex organic substances into simpler ones
decomposition
Recycling of nutrients within a plant
retranslocation or resorption
4 major groups of invertebrate detritivores, classified by body width
- Microfauna and microflora
- Mesofauna
- Macrofauna
- Megafauna
< 100 micrometers
Includes protozoans and nematodes inhabiting the water in soil pores
microfauna and microflora
> 20 millimeters
Dominated by earthworms and snails
megafauna
Between 100 micrometers and 2 millimeters
Includes mites, potworms, and springtails that live in soil air spaces
mesofauna
Between 2 and 20 millimeters
Includes annelid worms
macrofauna
Dead plant tissues
plant litter
A widely used approach to examine the rate of decomposition of dead plant tissues (plant litter) using litterbags;
Results are measured as % original mass remaining as a function of time
litterbag experiment
Areas of accumulated leaf litter in stream ecosystems;
Term also refers to litterbags used in stream decomposition experiments
leaf pack
Organic matter that, upon death, their bodies break up and dissolve within 15 to 30 minutes, too rapidly for any bacterial action to occur;
Provides a source of fixed carbon for decomposition;
Major sources of this organic matter are the free-floating macroalgae, phytoplankton, and zooplankton inhabiting the open water
dissolved organic matter (DOM)
Microbial breakdown of humus and other organic matter in soil to inorganic substances
mineralization
Conversion of an element from inorganic to organic form in microbial or plant tissue, rendering the nutrient unavailable to other organisms
immobilization
Difference between the rates of mineralization and immobilization
net mineralization rate
The ratio of carbon to nitrogen (grams of carbon per gram of nitrogen)
C/N ratio
Typical C/N ratios of plant litter and bacteria and fungi
For plant litter:
About 50:1 to 100:1
For bacteria and fungi:
About 10:1 to 15:1
Describes a region of the soil where plant roots function;
It is an active zone of root growth and death, characterized by intense microbial and fungal activity
rhizosphere
Dead organisms and other organic matter that, in the still and open water of ponds and lakes and in the ocean, drift toward the bottom;
On its way, they are constantly ingested, digested, and mineralized until much of the organic matter settles on the bottom in the form of humic compounds
particulate organic matter (POM)
Process of supplementing carbon to microbial decomposers in the rhizosphere, enhancing the decomposition of soil organic matter, and subsequently releasing mineral nutrients for plant uptake by microbial grazers
soil microbial loop
Farming systems that alternate periods of annual cropping with extended fallow periods;
Also referred to as shifting cultivation;
Fire is used to clear fallow areas for cropping
swidden agriculture
Fertilizer composed of organic matter derived from plants or animals
organic fertilizer
Fertilizer that provides nutrients in an inorganic or mineral form (referred to as chemical fertilizers when it is of synthetic origin)
inorganic fertilizer