Decomposition

Question 1

Define ‘allometry’.

Answer 1

Use robust relations between an easy-to-measure parameter (e.g., stem diameter) and a component of NPP, e.g., foliage biomass.

Question 2

How does ‘Eddy Covariance’ work?

Answer 2

The business end of a canopy tower:

a sonic anemometer plus a gas sampler connected to an IRGA allows CO2 flux to be estimated by ‘eddy covariance’.

Question 3

What is ‘Light Detecting and Ranging (LIDAR)’?

Answer 3

Vegetation heights and ground topography estimated by measuring time delay between transmission of a laser or radio pulse and detection of the reflected signal.

Question 4

How do satellite techniques for remote sensing work?

Answer 4

Reflectance of red and near-infra-red (NIR) radiation is altered by different vegetation types. This can be used to estimate ground cover using satellite-borne sensors.

Question 5

Define ‘Leaf Area Index (LAI)’.

Answer 5

LAI is the total one-sided area of leaves

per unit ground area.

Question 6

Define ‘ decomposition’

Answer 6

The breakdown of complex organic material into simple products.

Question 7

What is the importance of decomposition?

Answer 7

• Detritus is a primary energy & nutrient source for many microbes and animals
• Releases nutrients for subsequent plant, microbial, and animal consumption
• Facilitates soil formation
• Balance between primary production and decomposition influences ecosystem and global C budgets.

Question 8

Compare fermentation in eukaryotes with Bacteria and archaea.

Answer 8

Eukaryotes are only able to sustain fermentation for shorter periods.
Whereas bacteria and archaea can sustain fermentation for longer periods.

Question 9

What happens to a dead leaf?

Answer 9

1. Soluble materials are leached out.
2. UV radiation causes photo-oxidation.
3. Animals fragment the litter.
4. Animals and microorganisms metabolize the litter leading to mass loss.

Question 10

Define ‘aerobic’.

Answer 10

More complete decomposition and mineralisation to inorganic compounds.

Question 11

Define ‘anaerobic’.

Answer 11

Less complete decomposition, mixture of organic and inorganic compound.

Question 12

What do animals, as decomposers, do?

Answer 12

• Fragment detritus and mix soil.
• Produce waste products that microbes decompose.
• Host microbes in their digestive tracts.
• Stimulate decomposition.

Question 13

What do fungi, as decomposers, do?

Answer 13

• Main initial decomposers of dead plant material.
• Hyphae allow growth into new substrates and over surfaces.
• Secrete enzymes to allow fungal penetration of leaf cuticles into C- and nutrient-rich cells.
• Some can decompose lignin and other complex molecules.
• Dominate soil microbial biomass in acidic soils.
• Almost absent from anaerobic habitats - they require O2.
• Mycorrhiza-forming fungi are symbiotic with plant roots.

Question 14

What is destructive harvesting?

Answer 14

Collect plant material and dry in the oven. Weight it and plot graph. The rate of change = plant production rate.

Question 15

Define saprotrophs.

Answer 15

Organisms which live on dead material.