SOIL PROCESSES AND PLANT NUTRIENT CYCLING

Question 1

Senescence

Answer 1

• The final stage of leaf (or plant) development, involving the death of cells
• In leaves, this is often accompanied by colour change (due to the breakdown of chlorophyll)

Question 2

Translocation

Answer 2

• The process of redistribution of nutrients within a plant (e.g., from soil into stem and leaves)

Question 3

Retranslocation (resorption)

Answer 3

• The process of redistribution of nutrients from senescing parts of a plant into perennial tissues

Question 4

Litter

Answer 4

• (dead plant and animal matter) decomposes in the soil, where microbes break it down. This process releases essential nutrients like nitrogen, phosphorus, and carbon back into the soil, making them available for plants. Litter also supports the nutrient cycle.

Question 5

Order of Decomposition Rates:

Answer 5

Rapid Decomp:
1. Sugars, starches, simple proteins
2. Hemicellulose
3. Cellulose
4. Fats & waxes
5. Lignins & phenolic compounds
Slow Decomp:

Question 6

Fragmentation

Answer 6

• Physical break down of litter materials into smaller pieces
• Smaller pieces have greater surface area for microbial processes
• Mediated by soil ants, earthworms, etc

Question 7

Leaching

Answer 7

• The process by which water carries phosphorus deep enough into the soil that it is beyond the reach of plant roots

Question 8

Catabolism

Answer 8

• After fragmentation, microbes break complex organic molecules down into simpler organic molecules
• Done through the release of enzymes
• Lock & key or oxidation
• Chemical / biological process

Question 9

Humification

Answer 9

• Small amounts of decomposed organic compounds (sugars, hemicellulose, cellulose) remain, which serves to increase the proportion of decomposition-resistant lignins
• The remaining matter is called humus (dark in colour, and not identifiable)

Question 10

Mineralization

Answer 10

• The process by which organic phosphorus is converted into inorganic (plant-available) phosphate (PO43-)

Question 11

Rhizosphere

Answer 11

• Is the zone in a soil that is directly affected by root secretions and associated soil microorganisms

Question 12

Reclamation

Answer 12

• The process of converting disturbed or damaged land to its former or other productive uses
• Encompasses all disturbed components of an ecosystem, including but not limited to: soils, hydrology, flora, and fauna

Question 13

Restoration (ecological restoration)

Answer 13

• The process of assisting recovery and management of ecological integrity
• Includes consideration of biodiversity, ecological processes and structures, regional and historical context, and sustainable cultural practices

Question 14

Remediation

Answer 14

• The process of improving a contaminated site to prevent, minimize, or mitigate damage to human health and/or the environment (removal of contaminants)
• Encompasses strategies that remove, destroy, contain, and transform

Question 15

Nutrient Availability

Answer 15

• Limited organic matter can reduce the availability of nutrients for plants.

Question 16

Mineralization Rates

Answer 16

• Low organic matter results in slower mineralization = limited nutrient release.

Question 17

Water Availability

Answer 17

• Soils with less organic matter retain less water and drain more easily, reducing water in the rhizosphere.