Nitrogen and Ecosystem Nutrient Cycling. Nicole and Sarah Biogeochemistry of Northern Ecosystems March 2005. Cycling Essential Life Elements. Interactions between plants, animals, and soil microbes link the internal biogeochemistry of terrestrial ecosystems. Essential life elements:
Nitrogen and Ecosystem Nutrient Cycling
Nicole and Sarah
Biogeochemistry of Northern Ecosystems
Cycling Essential Life Elements
C, N, P, S, P, Ca, Mg, F
-often limiting and their supply may control NPP
intrasystem cycle is the annual cycle of nutrients in vegetation and is responsible for long-term retention of elements
Annual Nutrient Requirements for Growth
(Schlesinger, 1997 p.168)
General Nitrogen Information
abundance in the atmosphere, biosphere, and hydrosphere but it is the least
readily available to sustain life.
triple bond. Only a small number of N-fixing species have the energy required to
break apart this bond.
molecular form of nitrogen and Nr which is all the reactive nitrogen in the earths
atmosphere and biosphere.
The Nitrogen Cycle
Note: Nitrous oxide is N20.
Another View of the Nitrogen Cycle
the biosphere because of its
conversion back to its molecular
form, with a triple bond.
presence of NO3- or nitrate, 2)
availability of labile organic matter,
and 3) absence or low
important factor in controlling how
much denitrification goes on.
phytoplankton blooms and degree
Denitrification Reduces the Downstream N Transport (Galloway et al, 2003)
30-70% entering rivers denitrified
10-80% entering estuaries denitrified
>80% entering shelves denitrified
How Humans Have Impacted the Nitrogen Cycle
1. Generate Hydrogen
React H2 + N2 to produce NH3
N2 + 3H22NH3
3. Fossil Fuel burning- converts non reactive N into NOx
x1012 g yr-1
Discussion Questions- Potential Ecosystem Effects
Atmospheric Deposition of Nr(mg N m-2 yr-1)
Nitrogen Saturation and Ecosystem Degradation
higher than those under pristine conditions (10-50kg N ha-1yr-1)
Discussion Questions- Potential Solutions