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Page history last edited by gerryc 15 years, 8 months ago

E4. Resources are largely recycled in undisturbed communities.


Student Outcome: E4.1

Understand that the level of available resources will determine the productivity of the community.


The primary productivity of a community is the amount of biomass produced through photosynthesis per unit area and time by plants, the primary producers. Primary productivity is usually expressed in units of energy (e.g., joules m -2 day -1) or in units of dry organic matter (e.g., kg m -2 year -1). Globally, primary production amounts to 243 billion metric tons of dry plant biomass per year. The total energy fixed by plants in a community through photosynthesis is referred to as gross primary productivity (GPP). Because all the energy fixed by the plant is converted into sugar, it is theoretically possible to determine a plant's energy uptake by measuring the amount of sugar produced. A proportion of the energy of gross primary productivity is used by plants in a process called respiration. Respiration provides a plant with the energy needed for various plant physiological and morphological activities. The general equation for respiration is:


C6H12O6 + 6O2 >>> 6CO2 + 6H2O + released energy


Subtracting respiration from gross primary production gives us net primary productivity (NPP), which represents the rate of production of biomass that is available for consumption (herbivory) by heterotrophic organisms (bacteria, fungi, and animals).


Globally, patterns of primary productivity vary both spatially and temporally. The least productive ecosystems are those limited by heat energy and water like the deserts and the polar tundra. The most productive ecosystems are systems with high temperatures, plenty of water and lots of available soil nitrogen.


Source: http://www.physicalgeography.net/fundamentals/9l.html


Mean Net Primary Production by Ecosystem
Vegetation type Mean Net Primary Production
[g/(sq m x yr)]
Tropical rain forest 2200
Tropical seasonal forest 1600
Temperate evergreen forest 1300
Temperate deciduous forest 1200
Boreal forest 800
Savanna 900
Temperate grassland 600
Tundra 140
Cultivated land 650
Algal beds and reefs 2500



Source: http://rainforests.mongabay.com/03net_primary_production.htm


Here is the same sort of thing but done visually:


Here is a nice bright summary - basically saying the same thing but it looks nicer.


Student Outcome: E4.2

Explain why decomposers are essential in returning resources to the community.


Decomposers are an essential component of any ecosystem. Their main role is to recycle nutrients in dead organisms and their wastes. Most decomposers are bacteria and fungi. Without the decomposers, there could be no life since plants would run out of nutrients.


Source: http://www.chs.k12.nf.ca/science/b3201/WebCT-Copy/units/unit1-05.htm


Hey this is the best I could do! Not many people like to spend time videoing or making flash applications about decomposers - unless they want to sell something!

Go here to this commercial site - but it has a good summary of the carbon cycle and the role of decomposers.

Otherwise you could be a government department! Here is a rather confusing but, in the end, good website about decomposers.


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