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The Biogeochemical Cycles Fig 4.5 Periodic table of the elements. © 2003 John Wiley and Sons Publishers D. T. Krohne, General Ecology Fig 4.6 Idealized diagram of the geologic cycle, which includes the tectonic, hydrologic, rock and biogeochemical cycles. © 2003 John Wiley and Sons Publishers CO2 & CH4 15%/year Modified from D. T. Krohne, General Ecology The Carbon Cycle Fig 4.14 The Carbon Cycle. © 2003 John Wiley and Sons Publishers Fig 4.15 Idealized diagram illustrating photosynthesis for a green plant (tree) and generalized reaction. © 2003 John Wiley and Sons Publishers Fig 4.17 Global flux of carbon, 1850-1990. © 2003 John Wiley and Sons Publishers 50% fertilizer (Bacteria) Modified from D. T. Krohne, General Ecology Microbial mediated processes in the nitrogen cycle Nitrogen fixation Microbes fix nitrogen gas into ammonia that is incorporated into plant tissue Cyanobacteria live everywhere in the aquatic environment Nitrogen fixing bacteria in plant root nodules Ammonification (Mineralization) Refers to the breakdown of organic matter in order to release the organically bound nitrogen as inorganic (mineral) nitrogen in the form of ammonia Decomposition is the biological process that allows for the process Nitrifying bacteria (Nitrosomonas and Nitrobacter) Occurs in oxygen poor or anaerobic environments usually deep in the soil or in muddy sediments NO3- → NO2- → NO → N2O → N2 gas The complete denitrification process can be expressed as a redox reaction 2NO3- + 10e- + 12H+ → N2 + 6H2O Mangrove swamps are areas where denitrification happens From http://www.epa.gov/maia/html/nitrogen.html Fig 4.19 The global nitrogen cycle. © 2003 John Wiley and Sons Publishers Critical Thinking Issue – How are Human Activities Affecting the Nitrogen Cycle? Effects of increased use of nitrogen fertilizer: • Increased nitric acid in soil: • Leaching of magnesium and potassium • Increased aluminum levels • Plant root damage • Changes in microbe communities • Fish kills • Eutrophication of water bodies • Nitrates in drinking water • Global effects on plant based CO2 uptake © 2003 John Wiley and Sons Publishers Gaseous phase D. T. Krohne, General Ecology D. T. Krohne, General Ecology Modified from D. T. Krohne, General Ecology Phosphorous cycle in water Fig 4.20 The global phosphorus cycle. © 2003 John Wiley and Sons Publishers Ecosystems and the Gaia Hypothesis Ecosystem defined: a community of organisms and it’s corresponding abiotic environment through which matter cycles and energy flows • Wide variation in ecosystems • Boarders can be well defined or vague • Can be natural or artificial, managed or wild • Wide range in scale • Common to all ecosystems: energy flow and cycling of matter Gaia Hypothesis(es) • Life has greatly affected the planetary environment • This alteration has allowed life to persist • The Earth is a “super-organism” - Life controls the environment in a fashion that is equivalent to the way an organism controls its various systems • Evolution? Prepare for a quiz on the topic