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bio220lec21 - Lecture21: StaggField,UniversityofChicago...

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27/03/2013 1 Lecture 21: Biogeochemical cycles Stagg Field, University of Chicago Boeing B 29 under construction Connection between nuclear weapons and ecological research? Cold War with USSR set in right after 1945 US and USSR both expected to use nuclear weapons Radionuclide fallout would enter food chains— where would the compounds go? How would they affect organisms? OOPS! Sorry, Canada! B 36 replaces B 29 USSR replaces Japan H bomb replaces A bomb US National Labs (and U of T) researched radiation effects on organisms & ecosystems Pine oak forest irradiated by powerful gamma source (Cs 137 ), Brookhaven National Lab, Long Island, New York • Carbon cycle (will revisit later) • Nitrogen cycle (a gaseous cycle) • Human intervention: N fertilizer for crops • Phosphorus cycle (a sedimentary cycle) • Human interventions: mining, pollution Hydrologic cycle pools and fluxes (if time permits) • Human intervention: freshwater diversion for agriculture Aspects of some selected biogeochemical cycles Chemistry of the natural world Large organic molecules are constantly being synthesized, consumed, and broken down ( food and decomposer webs ) Chemical elements aren’t created or destroyed, but they do move around (and change oxidation states): moving around = cycling Cycle comprises pools and fluxes Stable, long lived compounds (like water and some pollutants) can persist much as elements do (but phase changes may be important) C, N, & P cycles All tied to hydrologic cycle Carbon cycle subsumes trophic webs N and P are the two elements most likely to limit plant productivity Key for pinkish figures from Begon et al.:
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