Terrestrial Ecology

Question 1

process that makes N2 biologically available

Answer 1

Nitrogen fixation

Question 2

Haber process

Answer 2

uses energy from fossil fuels to convert N2 to ammonia for fertilizers
fixes more nitrogen than any other anthropogenic process

Question 3

Sources of N2O

Answer 3

Nitrification and denitrification in oceans and tropical soils

Question 4

Sources of NH3

Answer 4

Domestic animals. ammonia is important for aerosol formation. Most ammonia returns to the earth in precipitation

Question 5

Largest terrestrial source of NO

Answer 5

Nitrification- from soils

Question 6

most NOx deposition occurs in

Answer 6

temperate zones

Question 7

How does NOx impact concentrations of other gases

Answer 7

NO affects the concentration of OH, which is the main oxidizing and cleaning agent in the atmosphere, so it impacts concentrations of other gases

Question 8

Impacts of nitrogen deposition

Answer 8

increased plant growth, decreased plant biodiversity, soil acidification, increased invasive species, increased damages from pests and frost, and increased N leaching to water bodies
may stimulate carbon uptake and storage
alter species dominance and competition, reduce diversity

Question 9

Nitrogen accumulation

Answer 9

plant production is limited by nitrogen (in most environments)-so they retain nitrogen that is deposited in ecosystems

Question 10

Nitrogen saturation

Answer 10

After a lot of nitrogen inputs, nitrogen supply exceeds demands. Associated with declines in forest productivity and increased mortality. Causes nitrogen losses.

Question 11

Nitrogen losses

Answer 11

Caused by nitrogen saturation, losses to stream water, ground water, and atmosphere.
Bad effects on plant and soil processes

Question 12

Nitrogen availabilty/losses In tropics-

Answer 12

nitrogen availability is high relative to demands- deposition can immediately cause nitrogen losses

Question 13

Four carbon pools that affect carbon cycling

Answer 13

land, atmosphere, oceans, sediments

Question 14

Terrestrial nutrient cycling: nitrogen inputs

Answer 14

Nitrogen fixation is main pathway for new nitrogen to enter an ecosystem

Question 15

Nitrogen fixers

Answer 15

bacteria that fix N2 –> NH4+, NH4+ is biologically available and used for growth. Nitrogen that is fixed by nitrogen fixers becomes available to others through litter/decomp

Question 16

Nitrogenase

Answer 16

enzyme that catalyzes the reduction of N2 to NH4. Has high energy requirement- only when bacterium has abundant carbohydrate supply.

Question 17

Symbiotic relationship between nitrogen fixers and plants

Answer 17

Plants provide carbohydrates, bacteria reside in root nodules- protected from O2. These have highest rates of nitrogen fixation

Question 18

Limitations on Nitrogen fixation

Answer 18

In closed canopy ecosystems- energy availability can constrain nitrogen fixation. Nitrogen fixation can be limited to high light environments, early succession, or limited canopy developments. Can also be limited by carbon, or other nutrients like phosphorus

Question 19

Conifer vs deciduous

Answer 19

Deciduous: broad leaves, flowers

Conifer: Needles/pines, cones

Question 20

HNO3 deposition

Answer 20

acidifies soil base cations leach from ecosystem.

Question 21

Internal cycling of nitrogen

Answer 21

Most nitrogen is available through decomposition. Most soil nitrogen is contained in dead matter. Microbes break down dead organic matter and release nitrogen as dissolved organic nitrogen (DON)

Question 22

Immobilization

Answer 22

Removal of inorganic nitrogen from the available pool by microbial uptake and chemical fixation. inorganic –> organic.
Microbes can take up NO3 and NH4+, but take up NH4+ more.

Question 23

Nitrifcation

Answer 23

Conversion of ammonium to nitrate-
nitrite acts as intermediate

NH4+ oxidized to NO2- and then NO3-

carried out by hetero and autotrophic nitrifiers

Question 24

nitrogen mineralization or ammonification

Answer 24

microbial growth is nitrogen limited, they secrete NH4+ into the soil,

Question 25

Rate limiting step of nitrogen mineralization

Answer 25

conversion of insoluble organic nitrogen to dissolved organic nitrogen- there are pools of insoluble nitrogen in soils

Question 26

Nitrogen limited microbes

Answer 26

Absorb or immobilize ammonium- immobilization

Question 27

Carbon limited microbs

Answer 27

Secrete NH4+ as waste

Question 28

Gross Mineralization

Answer 28

total amount of nitrogen released via mineralization | -regardless of if its absorbed or not

Question 29

Net mineralization

Answer 29

net accumulation of inorganic nitrogen occurs when microbial growth is more carbon limited than nitrogen limited approximately equal to nitrogen uptake by vegetation

Question 30

Most important determinant of the nitrification rate

Answer 30

Availability of NH4+

Question 31

Gaseous nitrogen loss from ecosystems

Answer 31

ammonia volatilization, nitrification, denitirification. Ammonia gas can be emitted from soils and senescing leaves

Question 32

NH3 flux from ecosystems

Answer 32

NH3 flux is low from most ecosystems- NH4+ maintained at low concentrations by plant and microbial uptake and binding to soil complexes. NH3 fluxes are large in ecosystems where NH4+ accumulates due to large nitrogen inputs.

Question 33

NO2-

Answer 33

can be absorbed through leaves and used in metabolism, or deposited in particulate form