The biogeochemical cycle is the processes by

which inorganic materials move from the atmosphere or soil into living organisms and back again.

Some materials reach ecosystems via the atmosphere (nitrogen, oxygen, water and carbon.)

Other elements are bound as minerals in rocks and soils.

Biogeochemical Cycles

http://www.slideshare.net/eyeznearz/ecosystems-how-do-they-work-8195195

Most chemical reactions and mineral transport within

organisms cannot occur without water. Water that sustains life on land is constantly cycled

between the air and the earth. Most of this cycling takes place through the processes

of evaporation, transpiration, and precipitation. The amount of water the atmosphere can hold

depends on abiotic factors such as temperature and air pressure.

Great diagram & information: http://water.usgs.gov/edu/watercyclehi.html

Water Cycle

Plants and animals use nitrogen to build nucleic

acids, structural proteins and enzymes. Nitrogen makes up 78% of the atmosphere. However, most living things cannot absorb

nitrogen from the atmosphere. They rely on nitrogen compounds found in the

soils. Nitrogen is converted by a process called the

nitrogen cycle.

Nitrogen

The nitrogen cycle has four major processes:

Nitrogen fixation: bacteria convert nitrogen gas into ammonia compounds

Ammonification: bacteria break down nitrogen containing amino acids from waste into ammonia

Nitrification: bacteria oxidize ammonia compounds to produce nitrites and nitrates

Denitrification: bacteria break down nitrates and release nitrogen gas back into the atmosphere

Diagram & description: http://www.shmoop.com/ecology/nitrogen-cycle.html

Nitrogen Cycle

During photosynthesis, plants use CO2 to

make glucose and release oxygen. Plants and animals use oxygen during

respiration to produce energy and release CO2. Photosynthesis and cellular respiration form

the basis of the oxygen-carbon cycle. The processes of photosynthesis and cellular

respiration generally balance each other out.

Carbon-Oxygen Cycle

The element phosphorous is essential in

molecules such as DNA and RNA. Phosphorous is mainly found on land in rocks

and minerals or dissolved in the ocean. As the rocks and minerals erode, phosphate is

released and absorbed by plants where it enters the food web.

Phosphorous moves through the ecosystem until it is deposited back into the soil or water through decomposition.

Phosphorous Cycle

In any given ecosystem with abundant water

and sunlight, the productivity of the ecosystem is limited by the available nutrients.

The limiting nutrient is the nutrient whose supply will limit overall productivity.

Nutrient Limitation

In terrestrial, or soil-based ecosystems,, the

limiting nutrient is usually nitrogen, phosphorous or potassium.

Other micronutrients in soil include: Ca, Mg, S, Fe or Mn.

In aquatic ecosystems, the limiting nutrient depends upon the type of water.

In oceans, nitrogen is often limited, but in freshwater, phosphorous is typically the limiting nutrient.

Limiting Nutrients in Ecosystems

On the Carbon-Oxygen cycle:

http://www3.epa.gov/climatechange/kids/basics/today/carbon-dioxide.html

Human Impact on Cycles