2-3 Nutrient Cycles: Nitrogen and Phosphorus

Question 1

What are the different nitrogen-containing molecules? Which are gasses? Inorganic? And which are available to plants?

Answer 1

Gasses:
- dinitrogen (N2) - 78% of atmosphere
- Ammonia (NH3)
- Nitrous Oxide (N2O) - powerful
- Nitrogen Dioxide (NO2)
- Nitric Oxide (NO)

Inorganic - available to plants :
- Ammonium (NH4+)
- Nitrate (NO3-)
- Nitrite (NO2-)

Question 2

Major reservoirs and fluxes in the nitrogen cycle?

Question 3

What is the nitrogen fixation by bacteria makes atmospheric N available to the biosphere?

Question 4

What are the needs for fixation?

Answer 4

Including P, energy, nitrogenase, and leghemoglobin, which maintains a low O2 environment in nodule

Question 5

What do humans have increased through the Haber-Bosch process and cultivation of legumes?

Answer 5

N-availabilty

Question 6

What are the three major processes that move biological N to the atmosphere

Answer 6

Volatilization, denitrification, combustion

Question 7

How does N deposition vary?

Answer 7

geographically, areas of high concentration

Question 8

What are the N-associated processes within ecosystems:

Answer 8

Mineralization, nitrification, and assimilation/immobilation, including associated bacteria metabilsm, inputs, and outputs

Question 9

Compare and contrast NH4+ and NO3-

Answer 9

interaction with soil particles, describes the consequences of nitrate leaching

Question 12

What are the different nitrgoen-containing molecules? Which are gasses? Inorganic? Which are available to plants?

Question 13

What are the major reservoirs and fluxes in the nitrogen cycle?

Question 14

What makes atmospheric N available to the biosphere?

Answer 14

Nitrogen fixation by bacteria

Question 15

What are the needs for fixation?

Answer 15

P, Energy, nitrogenase, leghemoglobin (maintain a low O2 environment in nodule)

Question 16

How have humans increased N-availabilty?

Answer 16

Through the Harbor-Bosch process and cultivation of legumes

Question 17

What are the three major processes that move biological N to the atmosphere?

Answer 17

volatilization, denitrification, combustion

Question 18

How does N deposition vary geographically, including high areas of concentration?

Question 19

What are the N-associated processes within ecosystems?

Answer 19

mineralization, nitrification, and assimilation/immobilization
include associated bacteria metabolism inputs and outputs

Question 20

Compare and contrast NH4+ and NO3-? What are their interactions with soil particles?

Question 21

What are the consequences of nitrate leaching?

Question 22

What are the major pools and fluxes of phosphorus?

Answer 22

There is no gaseous form of P so it does not cycle globally

Question 23

What is the soil P availability to plants like?

Answer 23

Soil P is unavailable to plants because it is immobilized, absorbed (chemically bound to the soil), or otherwise unavailable due to pH

Question 24

How does mycorrhizae and pH effect P availability to plants?

Answer 24

Mycorrhizae and/or pH changes due to liming can improve P availability to plants

Question 25

What is sediment a major source of?

Answer 25

P in aquatic systems and bio systems and bioavailable P increases with seasonal turnover, bottom feeding fish activity, & motorboats

Question 26

‘Peak phosphorus’

Answer 26

P must be mined for agriculture

Question 27

Colimitations

Answer 27

plants are typically more limited by N and microbes more limited by P.

Question 28

How does colimitation contribute to Liebig’s Law of the Minimum

Question 29

What does nutrient saturation lead to?

Answer 29

Nutrient saturation leads to plant diversity loss in terrestrial systems.
leads to eutrophic waters and contribute to dead zones

Question 30

What methods reduce nutrient export?