N loss cont

Question 1

gaseous losses of N?

Answer 1

ammonia volatilization (from ammonium in soil, NH4 -> NH3 (ammonia gas) + H+) - senescing leaves
- Fire (NOx, NH3, N2)
- denitrification (nitrates -> NO, N2O, N2)

Question 2

what is an important avenue of gas N loss in boreal?

Answer 2

wildlife
low N ecosystems lose most of their N

Question 3

consequences of ammonia NH3 gas output

Answer 3

interacts with acids in troposphere
reduces acidity of rain
deposited downwind

Question 4

consequences of NOX gas output (very reactive)

Answer 4

• high conc. contribute to O3 formation in troposphere
• stratoshperic ozone = good (but ozone hole bad)
• troposphere ozone= bad (smog, greenhouse gas)
• oxidation to nitric acid HNO3 a component of acid rain

Question 5

nitrous oxide (N2O)

Answer 5

• low reactivity (long lived): greenhouse gas: 150x> thermal adsorption capacity than CO2
• Converts to NO in stratosphere, destruction of “good” zone

Question 6

what is a dom form of loss in most systems?

Answer 6

DON is the dominant form of loss in most undisturbed systems

Question 7

NO3- leaching losses dominate when?

Answer 7

• in disturbed systems when plant uptake is reduced
• in systems where N» plant demand e.g. agriculture or weathered tropical soils
• in ecosystems with thawing permafrost

Question 8

what exacerbates leaching?

Answer 8

disturbance (e.g. harvesting)
look at hubbard brook ex

Question 9

where are most glboal nitrogen pools

Answer 9

• Most in atmosphere, but not biologically available (air - 78% N2)
  
  • Some in sediments/rocks, but not available

Question 10

2nd onward largest N pools?

Answer 10

• Inorganic N in ocean is next largest
  
  • Organic pools in plants and soils next largest (but miniscule relative to atmosphere pool)

Question 11

why are fluxes important - biol vs abiotic

Answer 11

• Several important biosphere-atmosphere N exchanges
  
  • Biological: fixation, denitrification, nitrification, ammonification/immobilization
  • Abiotic: industrial fixation, lightning, fossil fuel and biomass burning, decomposition

Question 12

what does
Biological cycling within natural systems outweigh (4-9x)

Answer 12

inputs/outputs (ie N cycle more closed than C cycle)

Question 13

Nitrogen Inputs - why increasing?

Answer 13

• Human caused inputs now = or exceed natural inputs
  
  • When inputs increase, so do outputs

Question 14

consequences of raising inputs

Answer 14

○ Consequences:
○ N saturation - n losses - opening of the N cycle
○ Atmosphereically active trace gases
○ N saturation: availability > demand -> increase losses via leaching
- eutrophication: uses up avail. O2
-dead zones; void invertebrates
- unsafe drinking water