Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Ecology - Soil Science > Nitrogen Cycle > Flashcards

Nitrogen Cycle Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

What does soil N decrease with?

A

Average soil temperature increase, decreasing by 2-3x every 10C rise due to increasing microbial activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why does permanent grass vegetation have higher N content than forests?

A

Dense rhizosphere promoting humus formation thus N immobilization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are organic forms of nitrogen in soils?

A

Proteins, nucleic acids, chitin, peptidoglycan and amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

When might organic nitrogen be unavaialble?

A

Restrictired to inaccessible micropores or binding to clay

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Urea decomposers…

A

Urease secreted as an extracellular enzyme, being 32-69% of bacterial production being urea-decomposers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Why might Urea be bad for soils?

A

Hydrolysis consuming H and increasing pH, where ammonia can volatise at high pH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How might NH4 be made available to plants?

A

Involved in CEC or immobilised by interlayers of clays

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is nitrification performed by?

A

Chemoautotrophs and heterotrophs, being oxidation of NH4 and organic N into NO2 and NO3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Which chemoautotrophs perform nitrification?

A

Nitrobacter, nitrosomonas, nitrosolobus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the process of chemoautotroph nitrification?

A

O2, H and NH4 required for NO2 formation with NH4 deprotonation to ammonia then oxidation to hydroxylamine, then nitroxyl formation then nitrite formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Requirements of nitrification…

A

Obligatory aerobic, requires O2 supply, optimal temperature range of 5-40, neutral-alklaline soils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What can abundant nitrification lead to?

A

Eutrophication, nitrosamine formation and methemoglobnemia in animals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How can NO3 be limited?

A

Slow-release fertilisers, like sulfur-coated urea: limits NH4 availabilit rate to nitrifiers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How might nitrogen be immobilised?

A

Microorganism fixation or NH4 ion assimilation into glutamate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How can Inorganic N be assimilated as NO3?

A

Reduction into NO2, NH4 depending on Mb cofactor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What can inorganic N assimlation as NO3 be inhibited by?

A

NH4, glutamine, glutamate due to preferential assimilation

17
Q

What does C:N ratio determine?

A

Mineralisation/Immobilisation equilibrium balance of N and NH4

18
Q

What does C:N ratio tell you?

A

How much N must be assimilated for every gram of C converted into biomass

19
Q

What is the typical C:N ratio for bacteria?

A

5:1 or 8:1

20
Q

Dissimilatory Nitrate Reduction

A

A form of aerobic respiraiton reducing nitrate via nitrite, NO2 and nitrous oxide as an electron acceptor forming N2

21
Q

How can nitrate be lost?

A

Runoff, assimilary reduction to organic N, dissimlatory reduction to NH4, ntirate respiration to NO2,, reduction to N2

22
Q

Nitrate Assimilation

A

NO3 reduction to NH4, then assimilation into aa

23
Q

How does DNR differ from denitrification?

A

DNR reduces nitrate to ammonia whilst nitrification to gas

24
Q

How does N fate depend on carbon concentraiton

A

If high, NO3 used as electron acceptor, favouring NH4 formation, or used as a terminal electron acceptor in metabolism when C is low

25
Q

Example of how C and NO3 balance influences microorganism community

A

Simultaneously Klebsiella dissimilates nitrate to ammonia whilse Pseudomonas NO3 to N2, Klebsella outcompeted with low C, thus denitrif dominant process

26
Q

What is a consequence of ammonium production?

A

Source of N in aerobic cnoditions, generates pyridine nucleotides increasing soil pH, NO2 is removed.

27
Q

Denitrification

A

Nitrogenous oxides like NO3 and NO2 are generated and used as terminal electron acceptors in absence of O2, reducing them to N2

28
Q

What do denitrification rates depend on?

A

O2, moisture, temperature, OM, C and NO3 ratio/content, especially O2 inhbiiting dentrifiying enzyme synthesis and electron flow

29
Q

Why does N2 oxidation to NO3 require energy?

A

Due to triple bond

30
Q

Industrial production of NO3

A

Haber-Bosch Method requires CH4 and extreme temperatures/pressure

31
Q

Biological nitrogen fixation…

A

Performed by legumes/rhizobium and water ferns as well as Azotobacter and Clostridium

32
Q

Azotobacter

A

GNB motile heterotroph being 4-7 micrometres forming resting body cysts growing in alkaline mesophylic soils

Ecology - Soil Science (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions