Nutrient cycling
1. Nutrient Cycling in Ecosystems
Following elements of an Ecosystem understand processes, function
Important for agricultural systems increased production + elements
Organic matter production (C) important and nutrients (N,P, etc.)
Create linkages between Biotic and Abiotic components Ecosystems
Biological communities processors of nutrients
Cycles called: Biogeochemical Cycles
Global Biogeochemical Cycles-Very Important climate etc. Closed system
2. Global Cycles – Summation all ecosystem cycles scale = Biosphere
Important to understand biogeochemical cycles various scales
At the Global scale everything averaged – linked to climate models
Local scale determine effect of cycling in one system having global effects
Example: Lake P Model (3-Compartment Model with 7 flux rates)
Each Compartment has a Pool of nutrients in standing stock
Flux rate is rate of movement of pool between compartments
3. Ecosystems are not isolated:
Fluxes between biogeochemical cycles different ecosystems
Transfer elements between ecosystems: Meteorological, Geological, Biological transport systems
4. How do we determine rates of flux materials construct biogeochemical cycles?
Radioactive Tracers- Example Phosphorus Lake
Stable Isotope Tracers (signatures where material came from)
Measure fluxes directly or through concentration gradients
5. Terrestrial Nutrient Cycles – Forests
Important for Forestry Management (Economic and ecological issues)
How does harvesting trees influence long-term productivity forest?
6. Forests accumulate nutrients differently over time
Take up nutrients quickly then more slowly
Accumulate leaves & wood
Example Pineland Canada
7. Age stand effects where nutrients going
Very mature forest >open canopy & understory vegetation
Example: Spruce forest Russia
8. Turnover times for nutrients cycled soils & forest Temperature-dependent
Important in terms nutrient limitation of forest production
9. Internal recycling within forest part of nutrient cycle
Also, fluxes out of forest
Nutrient losses forests several mechanisms
Stream transport
Gases released soils/plants (ammonia, sulfide gas, etc.)
Fires (gases & particulates)
Forest harvesting (nutrients wood)
Sometime interaction 2 effects harvesting-stream transport
Replacement nutrients after harvest > 50 years many forest-types
10. Globally Age soil define status nutrient “rich” or “poor”
Northern Hemisphere glaciated soils tend rich nutrients
Alluvial soils of Mississippi delta rich
Australia, India, South America old world soils poor
Plants adapted by being able to use nutrients efficiently
Nutrient Use Efficiency (NUE)
11. Important Global Biogeochemical Cycles
Significant Effect on Humans & vice versa
Sulfur Cycle
Nitrogen Cycle
Carbon Cycle
12. Sulfur Cycle
160% > Natural Levels- Emissions Burning Fossil Fuels (SO2)
Consequence:Acid Precipitation <5.6
13. Effects acid rain not new phenomenon: Tasmania Australia
1896-1922 copper smelter Ore mine
48% Sulfur
40% Iron
<3% Copper
Vegetation mortality 24hrs
Erosion topsoil lost
Nutrient pore soils
80 yrs later same
14. Some optimism on reduction of emissions oxides associated fossil fuels
1970 Passage Clean Air Act
15. Will forest & aquatic ecosystems recover effects acid rain? If yes, at what rate?
16. Nitrogen Cycle
Very important because Nitrogen major element limiting production biosphere
N2 abundant atmosphere (78%) only N2 fixers convert this N bioavailable N
Humans have doubled amount of bioavailable N in the Biosphere
Not evenly distributed N loading
Inputs of several forms of nitrogen depending on source-different effects
Nitrous Oxide: unreactive & persistent, Greenhouse gas, 0.25% increase/yr
Nitric Oxide, highly reactive, converted nitric acid, acid rain > W in US
Light reacts O2 & HC Ozone (smog) - Burning fossil fuels
Ammonia released from organic fertilizer waste
17. Major additions of nitrogen significant effects aquatic systems
18. Summary:
Nutrient cycle & recycle in ecosystems
Tracing nutrient cycles investigate important ecosystem processes
Logging or harvesting of biota storing elements can effect ecosystem function
NUE has allowed some species to adapt to low nutrient availability
Human activities are changing global biogeochemical cycles
Several cycles are being altered on a drastic scale with global consequences
These include sulfur cycle, nitrogen cycle, carbon cycle