Nutrient Cycles

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Nutrients

  • Nutrients flow through ecosystem in cyclic fashion
  • Macronutrients - water, carbon, oxygen, Nitrogen, Potassium, Phosphorus, Calcium, Iron, Magnesium and Sulfur.
  • Micronutrients - Chlorine, Copper, Boron, Zinc, Maganese, Silicon. 
  • Nutrients enter community through the activities of the primary producers who take in these materials and convert them into plant tissue.
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Primary Producers

  • Can only absorb charged particles (Ions) - K+, Ca++, Mg++ and Fe+++. made availible through wethering of rock.
  • Anions PO4---, NO3-,SO4---, are only availible to plants via the aerobic decomposition of the organic matter (hummus) in the soil - availibility of some ions influenced by PH of the soil.
  • Limestone and Chalk - Alkali
  • Sandstone - Acidic.
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Cycles

  • Nutrients move from FREE to IN USE via plant uptake and returned to the free compartment via decomposition of dead organic matter by microbes resulting in a cycle.
  • Closed Cycle - no losses or inputs - carbon, oxygen and nitrogen cycles - atmosphere serves as an unlimited reservoir, though locally these materials may be limiting.
  • Open cycle - nutrient reservoir is the substrate and losses result from leaching and fertiliser, toxic waste, often as a result of anthropogenic activities.
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Nitrate & Phosphate

  • Minerals most limiting for plant growth, especially in aqautic systems. 
  • Included in many fertilisers -> algal and microbial blooms -> eutrphication
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Uptake of Nutrients

  • Uptake of PO4---, NO3-, NH4+ and K+ aided by association between fungi and root - MYCORRHIZAE.
  • Mutualistic - plant gains nutrients, fungi gains sugar.
  • Nitrogen fixing bacteria living on root nodules also mutualistic.
  • Nurtient rich habitat - EUTROPHIC
  • Nutrient poor habitat - OLIGOTROPHIC
  • Intermediate habitat - MESOTROPHIC
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Anthropogenic Activity

  • Fertilisers - increase nutrient availibility and plant growth - restoration of china clay wastes
  • Tropical forests - Oligotrophic - nearly all nutrients in use rather than free
  • Pollutants - realeased into atmosphere - TOXIC - Not metabolised by organisms, so remain in food chains and accumulate in top consumers.
  • Eutrophication - release of large amounts of phosphate and nitrate into water -> algal and bacterial growth -> Lower o2 levels in aquatic fauna. B.O.D - measure of the amount of O2 required to support aerobic bacterial decomposition.
  • Other alterations to cycles - addition of heavy metals eg. Hg, Zn and Pb from mining and processing wastes. Some plants have developed tolerance. 
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