1. Lecture 9a Biogeochemical Cycles
Biogeochemical Cycles- Cycling of energy, and various chemical elements and compounds through the biosphere due to the feeding of organisms on each other
This includes: carbon, nitrogen, phosphorus, water...almost anything that temporarily inhabits a living thing

2. Ecosystem Ecology Food Webs:
The "levels" which organisms eat which one's "lower" on the chain"—
are called TROPHIC LEVELS (from the Greek troph, meaning "food" or "nourishment")
The Food Web reflects the flow of ENERGY and NUTRIENTS through ecosystems via the trophic levels.
The efficiency with which trophic levels convert energy from the previous trophic levels varies greatly with ecosystem, but usually ranges between 5% - 20%.

3. Organisms in the food web
Autotrophs: Organisms that can feed themselves by harnessing light energy to make organic molecules such as carbohydrates, proteins, lipids, and nucleic acids out of inorganic raw materials (such as carbon dioxide, water, nitrogen compounds, etc.)
Autotrophs = Primary Producers, because they are the first link in the food web/chain. Without their ability to capture light and "harness" it as solid, organic matter, life as we know it would not exist.
· Heterotrophs: Organisms that feed on other organisms to obtain energy. + =

4. Primary Producers are eaten by PRIMARY (1o) CONSUMERS.
Primary Consumers are eaten by SECONDARY (2o) CONSUMERS.
Secondary Consumers are eaten by TERTIARY (3o) CONSUMERS.
Tertiary Consumers are eaten by QUATERNARY (4o) CONSUMERS ...and so on, throughout the web.

5. Carbon Cycle
C6H12O6
All organic matter eventually is oxidized (burned) and converted back to carbon dioxide and water.
Photosynthesis

7. Soil Food Web
The community of organisms living all or part of their lives in the soil
Fueled by primary producers
plants, lichens, moss, photosynthetic bacteria, and algae
Or foodchain.rm

8. Photosynthesizers First trophic level Plants Algae Bacteria Role:
Capture solar energy to fix CO2
Add organic matter to soil (biomass such as dead cells, plant litter)

9. Decomposers Second trophic level Bacteria Fungi Protozoa Role:
Breakdown residue
Immobilize nutrients in their biomass
Create new organic compounds
Bind soil aggregates

10. Mutualists Second trophic level
Two organisms living in beneficial association
Bacteria
Fungi
Role:
Enhance plant growth
Fix nitrogen

11. Pathogens/Parasites Second trophic level Bacteria Fungi Nematodes
Arthropods
Role:
Promote disease
Consume roots
Parasitize nematodes or insects

12. Root-feeders Second trophic level Nematodes Arthropods Role:
Consume plant roots
Crop yield losses

13. Shredders Third trophic level Earthworms Arthropods Role:
Breakdown residue
Enhance soil structure
Provide habitat for bacteria in gut

14. Measurement of Microbial Activity
Counting
Direct counts
Plate counts
Activity levels
Respiration
Nitrification rates
Decomposition rates
Cellular constituents
Biomass C, N, or P
DNA/RNA fingerprinting

15. Fungi to bacteria ratios
Food Web Structures
Fungi to bacteria ratios
Grasslands:Ag soils = 1:1
Deciduous Forest 5:1 to 10:1
Conifer Forest 100:1 to 1000:1
Organism communities reflect their food source

16. Soil management affects the fungal and bacterial populations in soil
Fungi and bacteria differ in their responses to changes in agricultural practices.
Fungi are usually more sensitive to these changes. The fungal-to-bacterial ratio is therefore an indicator of environmental changes in the soil.
When plant residues are surface applied - fungi prosper because their hyphae are able to grow into the litter layer.
Tilliage - destroys large amounts of the fungal hyphae.
Incorporation of plant residues into the soil favors the bacterial population because the contact surface between the substrate and bacteria is increased.
Fungi are the predominant cellulose decomposers. Bacteria, which have a smaller C:N ratio than fungi, need food rich in nitrogen (e.g. green manure, legume residues).
A high nitrogen fertilizer favors the bacterial community in a soil
Substrate additions with a relatively wide C:N ratio enables growth of the fungal population.

17. Rates of Plant Residue Decomposition
Kind of material (FAST --> Sugar, starches, proteins --> hemicelluloses, cellulose, --> Fats waxes --> lignin SLOW
Rate decreases after the easy material has decomposed
Soil Conditions - water, temp., oxygen, nitrogen, phosphorus,
Decay Products = Energy (heat), carbon dioxide, N,P,S & Humus

18. Carbon Dioxide & Global Warming
The use of fossil fuels and practice of deforestation to meet the world's energy demands has lead to increasing concentrations of carbon dioxide (CO2) and methane (CH4) in the atmosphere.
Both gases absorb terrestrial infrared radiation and have the potential to affect earth's climate by warming it.

19. Sources of Atmospheric Carbon
Atmospheric carbon represented a steady state system, where influx equaled outflow, before the Industrial Revolution.
Currently, it is no longer a steady state system because the influx exceeds the outflow.
Therefore, we are experiencing an increase in atmospheric carbon, mainly in the form of CO2
Dennis L. Hartmann

20. Half of the solar energy that reaches Earth passes through the atmosphere and is absorbed at the surface.
About 90% of the infrared radiation emitted by the surface is absorbed by the atmosphere before it can escape to space.

21. The characteristics of the atmosphere that enable it to raise the temperature of the surface of Earth are:
1) atmosphere is transparent to sunshine
2) but is almost opaque to infrared radiation.
So the atmosphere lets in the heat from the sun, but is reluctant to let it escape again due to the “greenhouse gasses”

22. If CO2 is suddenly added to the atmosphere, it takes between 50 and 200 years for the amount of atmospheric CO2 to establish a new balance, compared to several weeks required for water vapor.

23. Soil Carbon Sinks
Large amounts of carbon have been released into the atmosphere through the conversion of grasslands and forests to agricultural and grazing land, as well as through unsustainable land practices.
Soils can regain lost carbon by absorbing or "sequestering" it from the atmosphere. But the ability of soils to act as carbon "sinks“ depends on sound land management.

25. Intensive Tillage No. 1 Environmental Enemy in Production Agriculture
D.C. Reicosky USDA - ARS -Morris Lab
Intensive Tillage

26. Keeps Carbon out of the atmosphere!
Holding carbon in the soil!
Keeps Carbon out of the atmosphere!

27. Gaining Carbon Losing Carbon Soil Carbon “C” : easy come, easy go!
Improved management can make C easy to come with more cropping intensity and/or cover crops and result in net carbon sequestration.
Improved management can make C slow to go with residue management and/or less tillage and result in net carbon sequestration.

28. Atmospheric Carbon as CO2
Fossil carbon cycle.
Biological carbon cycle.
Atmospheric Carbon as CO2
CO2
CO2
CO2 C
Energy from fossil fuels
Energy from bio-fuels
Plant biomass and roots left on or in the soil contribute to Soil Carbon or Soil Organic Matter and all associated environmental and production benefits.
Nonrenewable
Renewable

29. Sustainable agriculture
Global environmental quality depends on Conservation Agriculture and soil quality.
Tillage intensity
Carbon inputs
Carbon
Carbon
Our food supply
Sustainable agriculture =
Soil organic carbon

30. Soil is meant to be covered.
Manage soil carbon - make the world a better place.
D.C. Reicosky USDA - ARS -Morris Lab

31. The End