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

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%.

Organisms in the food web

 Autotrophs: Organisms that can feed themselves by harnessing light energy to make organic molecules   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.

+ =

Carbon Cycle

All organic matter (carbon compounds) on the earths surface is eventually oxidized (burned) and changed to carbon dioxide and water.

C 6 H 12 O 6

Photosynthesis

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  http://www.agron.iastate.ed

u/~loynachan/mov/ Or foodchain.rm



Photosynthesizers

   

Plants Algae Bacteria Role:

  Capture solar energy to fix CO 2 Add organic matter to soil (biomass such as dead cells, plant litter)

Decomposers

    Bacteria Fungi Protozoa Role:     Breakdown residue Immobilize nutrients in their biomass Create new organic compounds Bind soil aggregates

Mutualists

    Two organisms living in beneficial association Bacteria Fungi Role:   Enhance plant growth Fix nitrogen

Pathogens/Parasites

    Bacteria Fungi Nematodes Role:    Promote disease Consume roots Parasitize nematodes or insects

Root-feeders

 Nematodes  Role:  Consume plant roots  Crop yield losses

Shredders

   Earthworms Arthropods (millipedes) Role:    Breakdown residue Enhance soil structure Provide habitat bacteria in gut  Most millipedes eat decaying leaves & dead plant matter ,

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

Ratio of Fungi to Bacteria    Disturbed have a strong bacterial dominance.

Non-disturbed, fungi start to move in until habitats like prairies or your lawn have a relatively even proportion of fungi and bacteria in residence.

If shrubs and trees take over, the fungi in the soil .

build up and are strongly fungi dominated.

http://www.waldeneffect.org/blog/Fungi_to_bacteria_ratio/

Soil management affects the fungal and bacterial populations in soil

       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. Tillage - 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 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 ratio enables growth of the fungal population.

Garden Plants

   carrots, lettuce, and crucifers enjoy strongly bacteria dominated soils tomatoes & corn like soils that are closer to 1:1 (though still leaning a bit toward bacteria) perennials, shrubs, and trees like the soil to be full of fungi at ratios from 10:1 to 50:1.

     

Soil Biota

   only 1 to 5% of all biota on Earth have been named and classified. many unknown species are thought to reside in the soil. possible number of existing species of different groups are staggering: 1.5 million species of fungi, 300,000 species of bacteria, 400,000 species of nematodes 40,000 species of protozoa  Soil has potential for commercial exploitation in biotechnology, in bioremediation of polluted wastes, waters and land. Most clinically relevant antibiotics today originate from soil their products are being actively pursued. For example, enediynes are a natural toxin produced by soil known anticancer agents

Rates of Plant Residue Decomposition Kind of material ( FAST --> Sugar, starches, proteins --> SLOWEST Fats waxes --> lignin SLOWER hemicelluloses, cellulose, -->    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

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 (CO 2 ) and methane (CH 4 ) in the atmosphere. Both gases absorb terrestrial infrared radiation and have the potential to affect earth's climate by warming it.

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 CO 2 Dennis L. Hartmann

    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”

 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.

DYAD 

What are you going to do about “Climate Change”?

 

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.

Holding carbon in the soil!

Soil Carbon

“ C” :

easy come, easy go!

Deep plowing of organic matter might increase Carbon storage for the upper foot of soil.

Gaining Carbon Losing Carbon

Conservation tillage and cover crops may result in net carbon sequestration.

Intensive tillage results in carbon loss.

Fossil carbon cycle

.

Biological carbon cycle.

Atmospheric Carbon as CO

2 CO 2 Energy from fossil fuels

Nonrenewable

CO 2 Energy from bio-fuels C 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.

Renewable

CO 2

Soil is meant to be covered.

Manage soil carbon - make the world a better place.

D.C. Reicosky USDA - ARS -Morris Lab