APES 1: Biogeochemical Cycles

• involve the movement of matter via biological, chemical, and geological processes
• sources   * anything that releases more of the biogeochemical substance than it absorbs
• sinks   * anything that absorbs more of the biogeochemical substance than it releases

==Hydrologic (water) cycle==

• powered by the sun
• movement of water between sources and sinks
• water can move in its three phases (gas, liquid, or solid)
• solar heating
• evapotranspiration
• cool/cloud formation
• precipitation   * form of rain
• plant uptake/runoff/infiltration

==Carbon cycle==

• movement of atoms and molecules containing the element carbon between sources and sinks
• some reservoirs hold carbon for long and short periods of time
• cycles between photosynthesis and cellular respiration in living organisms
• decomposition: storage of carbon over millions of years
• the 7 processes that drive the carbon cycle   * photosynthesis & respiration     * producers uptake CO2 and respire some back through cellular respiration or death   * exchange, sedimentation & burial     * c exchanged between atmosphere and ocean   * extraction & combustion     * human activities (fossil fuels)     * fires & volcanoes

==Nitrogen cycle==

• movement of atoms and molecules containing nitrogen between sources and sinks
• nitrogen reservoirs hold compounds for a (relatively) short amount of time
• nitrogen fixation: the process in which atmospheric nitrogen is converted into a form of N (usually ammonia) that is available for uptake by plants
• the atmosphere is a major reservoir of N

==Phosphorus cycle==

• movement of atoms and molecules containing phosphorus between sources and sinks
• major reservoirs of phosphorus are rocks and sediments (no atmosphere component)
• phosphorus is naturally scarce in aquatic & terrestrial ecosystems - limiting factor

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