L3 - Biogeochemical Cycles

Question 1

What are the unique properties of water?

Answer 1

1. Forces of attraction - hydrogen bonding
2. Water exists as liquid over range of temps
3. Liquid water slowly changes temp
4. Takes a lot of energy for water to evaporate
5. Liquid water can dissolve compounds
6. Water expands when It freezes

Question 2

Residence time

Answer 2

average length of time a substance spends in a reservoir under steady state conditions

Question 3

Saturation

Answer 3

all pores are full of water and gravitational water is lost

Question 4

Field capacity

Answer 4

when water is not flowing out but there is still water in the soil

Question 5

Wilting point

Answer 5

no more water can be removed

Question 6

What accounts for difference between PET and AET?

Answer 6

PET is high at equator however in some regions such as north Africa there is no water for evaporation

Question 7

What are the photosynthetic pathways?

Answer 7

1. C3 (Calvin cycle)
2. C4 (Hatch-Slack)
3. Crassulacean Acid Metabolism (CAM)

Question 8

How does rubisco catalyse respiration and photosynthesis?

Answer 8

Binds to O2 in respiration and to CO2 in photosynthesis
(Depends on pH and temp)

Question 9

What is carbon fertilisation?

Answer 9

More co2 intake in shorter time period of stomata opening

Question 10

negative feedback of carbon fertilisation?

Answer 10

increase in photosynthesis increases carbon storage, thus lowers co2

Question 11

positive feedback of carbon fertilisation?

Answer 11

increase in temperature increases decomposition and thus co2 concentrations

Question 12

Could co2 increase lead to decreased transpiration?

Answer 12

There are no clear observations of this. Increase in plant leaf area seems to counteract any decrease

Question 13

How can co2 increase improve water use efficiency?

Answer 13

More co2 is taken in during stomata opening and there is relatively less water loss.

Question 14

How does increased co2 impact stomata?

Answer 14

• Causes a decrease in stomatal conductance (gs) (rate of carbon intake)
• Smaller stomata
• Less water loss from stomata

Question 15

Why is nitrogen important?

Answer 15

1. Influences rate of photosynthesis - linear correlation between N in leaves and photosynthesis rate
2. Greenhouse effect
3. Role in ozone later - stratosphere and troposphere
4. Likely source of Cloud Condensation Nuclei (particles on which water vapour condenses)

Question 16

How does chlorophyll facilitate photosynthesis?

Answer 16

Enables light absorption. Contains C,H O, N, and P

Question 17

What form of N do plants and algae require?

Answer 17

One of ammonia or nitrate

Question 18

Denitrification

Answer 18

conversion nitrate to nitrogen gas by soil microbes when oxygen is not present