Ecology - Lecture 19 - Nutrient Cycles

Front 1

What 2 macro levels cycles do Biochemical processes occur on?

What kind and type of nutrients are found on each cycle?

Back 1

1) Global Cycles
Volatile nutrients
EXA: {N, C, O}

2) Local Cycles
Nonvolatile nutrients
EXA: {P, K}

Front 2

What are 2 ways nutrient cycling fluctuates in an ecosystem?

Back 2

1) Nutrients can accumulate or decline over time.

2) Nutrient uptake changes during succession.

Front 3

What are 5 examples of limiting nutrients within trees?

Which one is the most abundant?

Back 3

[24.10]

1) Nitrogen (N)
2) Potassium (K)
3) Calcium (Ca)
4) Phosphorus (P)
5) Magnesium (Mg)

*Nitrogen is the most abundant

Front 4

What example was used for how nutrients can accumulate/decline in an ecosystem?

What trend was seen?

Back 4

Jack pine forests in Canada. [24.10]

As the age of the tree increased, the amount of above-ground tree nutrients increased.

Nitrogen was the most abundant.

Front 5

What example was used for how nutrient uptake changes during succession?

Back 5

Spruce forest in Russia. [24.11]

Front 6

How does logging and deforestation affect nutrient cycles?

What example was cited for this?

Back 6

- Increases loss rates

[EXA] Stream-water nitrogen content following clear cuts.
- Runoff and nitrate concentration in streams greatly increased after deforestation.

Front 7

NPP (Net Primary Production) of Nitrogen is _____ in oceans and many terrestrial ecosystems.

Back 7

...limited...

Front 8

What percentage of the atmosphere is composed of nitrogen approximately?

Back 8

78%

Front 9

Name that compound:

NH₄⁺

Back 9

Ammonium

Front 10

Name that compound:

NO₃-

Back 10

Nitrate

Front 11

Name that compound:

NO₂-

Back 11

Nitrite

Front 12

Name that compound:

N₂

Back 12

Atmospheric nitrogen

Front 13

What are the 2 forms of nitrogen that plants can assimilate?

Back 13

1) Ammonium (NH₄+)
2) Nitrate (NO₃-)

Front 14

Nitrogen Fixation:

What is the chemical equation for Nitrogen Fixation?

Describe the process in words.

Back 14

N₂ → NH₄+

Atmospheric nitrogen to Ammonium

Front 15

Nitrogen Fixation:

What 2 types of bacteria are responsible for nitrogen fixation?

What type of condition is this process most efficient under?

Back 15

N₂ → NH₄+

1) Free living soil bacteria (e.g. Azotobacter)

2) Symbiotic bacteria in root nodules (e.g. Rhizobium)

Most efficient under *anaerobic* conditions. (i.e. low oxygen)

Front 16

Nitrification:

What is the chemical equation for Nitrification?

Describe the process in words.

Back 16

NH₄+ → NO₂- → NO₃-

Oxidation of ammonium to *nitrite*

Further oxidation of nitrite to *nitrate*

Front 17

Nitrification:

What types of bacteria (in terrestrial and ocean environments) assist in each stage of this process?

Back 17

NH₄+ → NO₂- → NO₃-

NH₄+ → NO₂
- Nitrosomonas in soil
- Nitrosococcus in ocean

NO₂- → NO₃-
- Nitrobacter in soil
- Nitrococcus in ocean

Front 18

Nitrification:

Under what type of conditions is this process most efficient?

Back 18

*Aerobic* conditions.

Oxygen is required for oxidation.

Front 19

Summarize the 3 step process of nitrogen assimilation by plants.

Back 19

1) Inorganic nitrogen reduced to organic forms. (NH₄+, NO₃-, NO₂-)

2) Used in synthesis of amino acids and proteins

3) Organic forms move up food chain.

Front 20

Ammonification:

What is the chemical equation for ammonification?

Back 20

(amino acids), (proteins) → NH₄+

Amino acids and proteins are converted to ammonium.

Front 21

Ammonification:

Describe how the process occurs.

How is this process useful for plants?

Back 21

Dead organic material is broken down by decomposers
- Aerobic and anaerobic bacteria/fungi.

They convert organic nitrogen back to ammonium.

*Once converted, nitrification can then make nitrogen available for plants again.

Front 22

Denitrification:

What is the chemical equation for denitrification?

Back 22

NO₃- → N₂, NO, N₂O

Nitrate is converted to atmospheric nitrogen, nitric oxide, and nitrous oxide.

Front 23

Denitrification:

Where does this process occur?

What types of products are produced?

Back 23

- Occurs in waterlogged, anaerobic soils, oxygen-depleted sediments and bottom waters.

- NO₃- reduced to NO(g) escapes as a gas.

- Further reductions produce N₂O and N₂; which escape as gasses.

Front 24

Denitrification:

What might the process of denitrification help explain?

Back 24

Nitrogen limitations in:
- oceans
- swamps
- marshes

Front 25

Be able to reproduce the Nitrogen Cycle slide from this lecture (#19; slide 5 of 10).

Back 25

...okay

Front 26

Human Impacts on the Nitrogen Cycle:

Human activities are changing the _____ of the atmosphere.

Back 26

...composition...

Front 27

What are 2 forms of nitrogen that have a negative affect on atmospheric conditions?

What effect do they have?

Back 27

1) Nitrous Oxide (N₂O(g))
- Absorbs heat and is a "greenhouse gas"

2) Nitric Oxide (NO)
- Contributes to smog and acid rain

Front 28

What are 3 ways that humans are impacting the Nitrogen Cycle?

Back 28

1) Changing the *composition* of the atmosphere

2) Increase nitrogen *deposition* on land and in oceans.

3) Promote *eutrophication* of aquatic systems.

Front 29

Define:

Eutrophication

Back 29

An increase in chemical nutrients (compounds containing nitrogen or phosphorus) in an ecosystem.

Front 30

What 2 examples of eutrophication in aquatic systems did we talk about?

Back 30

1) Algal bloom in Orielton Lagoon, Australia (1994)
- Increase in nutrients creates a green soup environment.

2) Fish kills in Salton Sea
- Too much nutrients fuels growth that uses up all the oxygen, resulting in massive fish kills.

Front 31

What has high nitrate concentration in drinking water been linked to?

What is the maximum allowable level of nitrate in drinking water?

Back 31

A variety of human diseases, including several cancers.

Maximum allowable level = 10 ppm.

Front 32

Phosphorus Cycle:

Describe the 3 step process of the phosphorus cycle.

Back 32

1) Released through the weathering of rocks.

2) Often washed down streams and rivers into oceans.

3) Limits plant growth in many freshwater aquatic ecosystems.

Front 33

Name that compound:

N₂O (g)

Back 33

Nitrous oxide

Front 34

Name that compound:

NO (g)

Back 34

Nitric oxide

Front 35

Plants assimilate phosphorus as _____ ion.

Back 35

...phosphate...

PO₄³-

Front 36

Name that compound:

PO₄³-

Back 36

Phosphate ion

Front 37

What are 3 ways the human body uses phosphorus?

Back 37

1) Nucleic acids

2) Energy transfer systems (ATP)

3) Cell membranes