Ecology final exam study guide - Ecology final exam study...

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Ecology final exam study guideChapter 24: Nutrient CyclesOverview: • Human impacts on nutrient cycling • Nutrient pools and fluxes • Nitrogen cycles • Sulfur cycles • Impacts of acid rain on forests and riversThe cycling of elements is a major aspect of how ecosystems functionGlobal problemFigure 24.1Element cycles interact with each other; e.g. acid rainA hypothetical phosphorous cycle in a simple lake ecosystemCan breakdown by individual bynutrientcompartments(pools)-Hownutrients move from pooltoanother known asflux ()Output(133)Input (133) Stable stateElements move through an ecosystem via different pathwaysSources of elements: 1. Air (nitrogen) 2. Weathering of rocksChapter 24:Nutrient cycles and recycle in ecosystems. Humans are drastically modifying these nutrient cycles.Nutrient use efficiency is higher in low-nutrient systems, and plants have evolved mechanisms to recycle nutrients efficiently.Nutrients often set some limitation on the primary and secondary productivity of a population or community and nutrient additions as fertilizer have become increasingly common in agriculture and forestry.Biogeochemical cycles: the movement of chemical elements around an ecosystem via physical and biological processes. Bioelements: the chemical elements that move through living organismsNutrient cycles are closed on a global scale but open on a local scale.All nutrients reside in compartments which represent a defined space in nature.A compartment contains a certain quality, or pool of nutrients in the standing crop.Compartments exchange nutrients and thus we must measure the uptake and outflow of nutrients for each compartment. The rate of movement of nutrients between two compartments is the flux rate and is measured as the quality of nutrient passing from one pool to another unit of time, the flux rates and pool sizes together define the nutrient cycle within a particular ecosystem.Nutrients come in and out of an ecosystem through meteorological, geological, or biological transport Chapter 24Many freshwater ecosystems are limited in productivity by phosphorus. Phosphorus as well as other nutrients tend to accumulate in the sediment of lakes such that continual nutrient inputs are required maintain high productivity. The key problem in aquatic ecosystems is that limited nutrients such as phosphorus can be locked up in sediments, thus restricting primary production.Nutrient cycle typesLocal nutrient cycle: operates with in a n ecosystem, have no mechanism for long distance (Phosphorus cycle)-nonvolatileGlobal Nutrient Cycles:involve exchanges between the atmosphere and the ecosystem. (gaseous cycles: nitrogen, carbon, oxygen and water)-VolatileNutrient cycles in Forests:Not all forest successions produce the same pattern of changes in nutrient cycling but in general nutrient cycling varies with forest age.

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