1. The Biogeochemical Cycles

2. The Cycling of Chemical Elements in Ecosystems
Nutrient cycling involves both the biotic and abiotic portions of an ecosystem.
These are called the biogeochemical cycles.

3. Biological and geologic processes move nutrients between organic and inorganic compartments
There are four main reservoirs of elements and processes that transfer elements between reservoirs.
Reservoirs are defined by two characteristics, whether it contains organic or inorganic materials, and whether or not the materials are directly usable by organisms.

5. The Water Cycle: more of a physical process than a chemical one.

6. The Carbon Cycle
Two natural processes cycle carbon through the ecosystem.
Photosynthesis; autotrophs take in CO2 and produce organic compounds available then for consumers.
Cellular Respiration; both autotrophs and heterotrophs use cellular respiration to convert energy rich organic compounds into ATP to power cellular functions.

7. The Carbon Cycle

8. The Nitrogen Cycle
Nitrogen enters ecosystems through two natural pathways.
Atmospheric deposition, where usable nitrogen is added to the soil by rain.
Nitrogen fixation, where certain bacteria convert N2 to minerals that can eventually be used by plants to produce nitrogenous organic compounds.

10. The direct product of Nitrogen Fixation is ammonia, which picks up H+ and becomes an ion, ammonium in the soil.
Some bacteria break down detritus and animal waste producing ammonium through Ammonification
Certain bacteria convert ammonium into nitrate, a process called Nitrification.
Nitrate can be used by plants.
Some bacteria take oxygen from the nitrate and release N2 back into the atmosphere called Denitrification.

11. WHAT IS NEEDED (Reactants) WHAT IS PRODUCED (Products)
PROCESS
WHAT IS NEEDED (Reactants)
WHAT IS PRODUCED (Products)
WHAT DOES THE WORK?
NITROGEN FIXATION
Nitrogen Gas (N2)
Usable nitrogen:
Nitrates (NO3-) made in roots of legumes and Ammonium (NH4+) and in the soil.
Nitrogen fixing bacteria in soil and in legume roots.
AMMONIFICATION
Detritus and waste
Ammonia
Decomposers (Bacteria and Fungus)
NITRIFICATION
Ammonium
Nitrites (NO2-) & NO3-
Nitrifying Bacteria
ASSIMILATION
Nitrates
Any nitrogen based compound needed by plants and animals. Nitrogen is used to make amino acids.
Chemical reactions in the organism.
DENITRIFICATION
Excess nitrates
Nitrogen Gas
Denitrifying Bacteria

12. Review of chemical cycling in ecosystems.

13. Decomposition rates largely determine the rates of nutrient cycling
The rate at which nutrients cycle in an ecosystem depends on the rate of decomposition.
Decomposition can take up to 50 years in the tundra, while in the tropical forest, it occurs much faster.
Quantities of nutrients in the soil of different ecosystems also varies, depending on the rate of absorption by the plants.

14. Nutrient cycling is strongly regulated by vegetation
In a terrestrial ecosystem most of the mineral nutrients cycle within the ecosystem.
In addition to the natural ways, nitrogen-containing fertilizer contributes to the total amount of nitrogen materials in ecosystems.

15. The End see it wasn’t that bad 