Energy and matter in ecosystems

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Energy flows and materials cycle

Laws of ThermodynamicsFirst Law of Thermodynamics – Energy is neither created

or destroyed. It may be converted from one form to another. Law of Conservation of energy.

Describe how this concept relates to ecosystems.

Second Law of Thermodynamics – In any energy conversion some energy is lost. Where does it go?

Most is lost as heat.

Without the addition of energy systems move toward increasing disorder. Entropy is a measure of the degree of disorder.

Relate this concept to ecosystems.

Carbon cycle

http://www.globalchange.umich.edu/globalchange1/current/lectures/kling/carbon_cycle/carbon_cycle.jpg

Pools

Fluxes (flows)

Phosphorous CycleComes from the weathering ofrocks.

Phosphorous CycleInorganic initially from rock material. Phosphate ion

(PO43-)

Organic form when taken up by plants and combined with organic molecules.

May combine with iron, aluminum, or calcium. Will not be available to the plants in this form.

Can only be recycled if deposited as wastes from the ecosystem in which originated.

Phosphorous CycleContained in fertilizers and detergents. Most detergents

are now phosphate free.Causes water bodies to become overfertilized if it runs

off land surfaces.Causes eutrophication of water bodies.Cycle has become accelerated due to mining and over

use.

Nitrogen Cycle

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Nitrogen CycleMain pool of Nitrogen is in the atmosphere. 78% of

atmosphere is nitrogen.This is non-reactive nitrogen. Unusable to plants in this

form.Reactive nitrogen (Nr) in form of ammonium ions (NH4

+) or nitrate ions (NO3

-) are able to be taken up by plants.Once taken up by plants the nitrogen moves through the

food web.Nitrogen wastes return as ammonium, nitrifying bacteria

converts this to nitrates which is then used by the plants.

Nitrogen CycleNitrogen Fixation – bacteria on roots of certain

plants can utilize the non-reactive nitrogen through the process of nitrogen fixation. Rhizobium bacteria live on the roots of plants in the legume family. Examples: peas, soybeans, lentils, clover.

Farmers plant these crops in order to access the nitrogen from the atmosphere.

Root Nodules

soils.usda.gov

Atmospheric nitrogen fixation – Through lightning discharges, nitrogen gas is converted to ammonium and falls to the ground as precipitation. Early spring snows are referred to as “poor man’s fertilizer.”

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Industrial fixation – through the process of manufacturing fertilizer. Haber – Bosch process.

Fossil fuel combustion – oxidation of nitrogen from burning fossil fuels. Created nitrogen oxides which leads to acid precipitation.

Nitrogen Cycle

Denitrification – In soils low in oxygen the microbes take oxygen from the nitrates (NO3

-). Nitrogen is then given up to the atmosphere. Since nitrogen is necessary for plant growth farmers try to avoid this process. Plowing in the spring restores oxygen.

Waste treatment plants promote denitrification to eliminate the nitrogen since N2 overfertilizes the waterways.

Human ImpactsCarbon – Somewhat obvious at this point. Discuss.

•Phosphorous - Contained in fertilizers and detergents. Most detergents are now phosphate free.

- Causes water bodies to become overfertilized if it runs off land surfaces.

- Causes eutrophication of water bodies.- Cycle has become accelerated due to mining and

over use.

Nitrogen – Planting legumes increase nitrogen fixation. Non-

luguminous plants (corn, wheat, potatoes, etc.) need manufactured nitrogen fertilizers.

Burning fossil fuels fixes nitrogen from the atmosphere.Increase the rate of natural fixation by 1.5x.Causes acid precipitation and deposition which leaches

minerals from soils.Increased Nox in atmosphere leads to ozone pollution,

stratospheric ozone depletion, and climate change.Runoff of nitrogen leads to algal blooms in waterways