1. Biogeochemical Cycles
Ecosystems
Biogeochemical Cycles

2. KEY CONCEPT 1
Ecosystems consist of nonliving (abiotic) and living (biotic) components.

3. KEY CONCEPT 2
An ecosystem survives by a combination of energy flow and matter recycling.

4. KEY CONCEPT 3 Earth is a Closed System! Biosphere Carbon cycle
Phosphorus
Nitrogen
Water
Oxygen
Heat in the environment
Heat

5. BIOGEOCHEMICAL CYCLES: ABIOTIC CYCLES
GLOBAL RECYLING - A closed pathway where matter cycles from the nonliving environment to living and then back again for reuse.
Key feature- nutrients recycle through the earth’s air, land, water, and living organisms.
Nutrients are the elements and compounds that organisms need to live, grow, and reproduce.
The overall rate of nutrient movement is limited most by decomposition.
The rate of nutrient loss is a key characteristic in any ecosystem.

6. Overview of Nutrient Cycling
Plants
Consumption
Overview of Nutrient Cycling
Herbivore
Assimilation
Feces or urine
Death
Death
Detritus
Uptake
Soil nutrient pool
Decomposer
food web
Loss to erosion or leaching into groundwater

7. Water Cycle Condensation Transpiration Evaporation Precipitation
Rain clouds
Transpiration
Evaporation
Precipitation to land
Transpiration from plants
Precipitation
Precipitation
Evaporation from land
Evaporation from ocean
Surface runoff (rapid)
Runoff
Precipitation to ocean
Infiltration and Percolation
Surface runoff (rapid)
Groundwater movement (slow)
Ocean storage

8. Water Cycle Causes wind currents
There are strong forces of attraction between molecules of water.
Water exists as a liquid over a wide temperature range.
Liquid water changes temperature slowly.
It takes a large amount of energy for water to evaporate.
Liquid water can dissolve a variety of compounds.
Water expands when it freezes.
Water Cycle
Water has greatest influence of all non-living components

9. Effects of Human Activities on Water Cycle
We alter the water cycle by:
Withdrawing large amounts of freshwater.
Clearing vegetation and eroding soils.
Polluting surface and underground water.
Contributing to climate change.

10. Carbon Cycle Combustion: Photosynthesis and Cellular respiration:
Burning- CO2
Fossil fuels –hydrocarbons
Volcanic Action
Forest Fires
Photosynthesis and Cellular respiration:
O2   CO2
Erosion:
CaCO3  shells  limestone

11. Effects of Human Activities on Carbon Cycle
We alter the carbon cycle by adding excess CO2 to the atmosphere through:
Burning fossil fuels.
Clearing vegetation faster than it is replaced.
Figure 3-28

13. Greenhouse gases Carbon dioxide Water Methane Nitrous oxide
Sulfur hexafluoride

14. Most Important Greenhouse Gases
GHGs Source Examples
Water: H2O Oceans, rivers, plants, soil
Carbon Dioxide: CO2 Combustion of fossil fuels, plant respiration, oceans, volcanoes
Methane: CH4 Mining operations, combustion, animals, wetlands, landfills
Other GHGs : Nitrous oxide (N2O), Ozone (near surface),
Learn more about GHGs:
Source: U.S. EPA 2005

15. Nitrogen Cycle
Availability of Nitrogen is a limiting factor for primary productivity
78% N gas in atmosphere
unusable

16. Nitrogen Cycle Ammonification Decomposition by bacteria during decay
Bacteria can “fix nitrogen” which means they break apart nitrogen gas and convert it into ammonia or ammonium.
Assimilation
Absorption and incorporation of nitrogen by plants
These nodules are called rhyzomes. They are where the nitrifying bacteria reside. They have a symbiotic relationship with the plant
Nitrification
Ammonia to nitrates and nitrites by bacteria
Then can be assimilated by plants
Denitrification
Denitrifying bacteria convert nitrates back into N2

17. Effects of Human Activities on the Nitrogen Cycle
We alter the nitrogen cycle by:
Adding gases that contribute to acid rain.
Adding nitrous oxide to the atmosphere through farming practices which can warm the atmosphere and deplete ozone.
Contaminating ground water from nitrate ions in inorganic fertilizers.
Releasing nitrogen into the troposphere through deforestation.

18. Effects of Human Activities on the Nitrogen Cycle
Human activities such as production of fertilizers now fix more nitrogen than all natural sources combined.

19. Phosphorous Cycle
No gaseous component (from land to sediment and back to land only)
Erosion releases phosphate soil plants
Decomposers phosphate  soil
Deposited in oceanic sediment  unavailable for years
Fertilizers, run off containing animal wastes, and sewage aquatic ecosystems

20. The Phosphorous Cycle

21. Effects of Human Activities on the Phosphorous Cycle
We remove large amounts of phosphate from the earth to make fertilizer.
We reduce phosphorous in tropical soils by clearing forests.
We add excess phosphates to aquatic systems from runoff of animal wastes and fertilizers.

22. The Sulfur Cycle

23. Effects of Human Activities on the Sulfur Cycle
We add sulfur dioxide to the atmosphere by:
Burning coal and oil
Refining sulfur containing petroleum.
Converting sulfur-containing metallic ores into free metals such as copper, lead, and zinc releasing sulfur dioxide into the environment.

24. Acid Precipitation
Rain, snow or fog that has a pH value of less than 5.6 because of the carbon dioxide from air dissolved in it
Any rainfall has a pH value less than 5.6 is defined as acid rain

25. Acid Precipitation
When gas pollutants e.g. sulfur dioxide, nitrogen dioxide dissolve in rain water, various acids are formed.
CO2 + H2O  H2CO3 (carbonic acid)
SO2 + H2O  H2SO3 (sulphorous acid)
NO2 + H2O  HNO2 (nitrous acid) HNO3 (nitric acid)

26. CAUSES OF ACID RAIN