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Nutrient Cycles in Ecosystems. Biogeochemical Cycle  The flow of a nutrient from the environment to living organisms and back to the environment  Main.

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Presentation on theme: "Nutrient Cycles in Ecosystems. Biogeochemical Cycle  The flow of a nutrient from the environment to living organisms and back to the environment  Main."— Presentation transcript:

1 Nutrient Cycles in Ecosystems

2 Biogeochemical Cycle  The flow of a nutrient from the environment to living organisms and back to the environment  Main reservoir for the nutrient is in the environment

3 geochemical cycle Main nutrient reservoirs in the environment fraction of nutrient available to ecosystem primary producers herbivores, carnivores, parasites detritivores, decomposers Fig , p.852

4 Three Categories  Hydrologic cycle Water Water  Atmospheric cycles Nitrogen and carbon Nitrogen and carbon  Sedimentary cycles Phosphorus and sulfur Phosphorus and sulfur

5 Hydrologic Cycle Atmosphere Ocean Land evaporation from ocean 425,000 precipitation into ocean 385,000 evaporation from land plants (evapotranspiration) 71,000 precipitation onto land 111,000 wind-driven water vapor 40,000 surface and groundwater flow 40,000 Figure Page 853

6 EVAPORATION PRECIPITATION TRANSPIRATION dripping, trickling down along stems falling through to ground interception by plants surface pooling, etc. infiltration of soil moisture in soil seepage, percolation groundwater storage DEEP OUTFLOW overland flow lateral flow base flow STREAM OUTFLOW Fig , p.853

7 Water Use and Scarcity  Most of Earth’s water is too salty for human consumption  Desalinization is expensive and requires large energy inputs  Irrigation of crops is the main use of freshwater

8 Fig , p.855

9 Negative Effects of Irrigation  Salinization, mineral buildup in soil  Elevation of the water table and waterlogging  Depletion of aquifers

10 Aquifer Problems Figure Page 855

11 Carbon Cycle  Carbon moves through the atmosphere and food webs on its way to and from the ocean, sediments, and rocks  Sediments and rocks are the main reservoir

12 Figure Page 856 diffusion between atmosphere and ocean bicarbonate and carbonate in ocean water marine food webs marine sediments combustion of fossil fuels incorporation into sediments death, sedimentation uplifting sedimentation photosynthesis aerobic respiration Carbon Cycle - Marine

13 Carbon Cycle - Land photosynthesis aerobic respiration terrestrial rocks soil water land food webs atmosphere peat, fossil fuels combustion of wood sedimentation volcanic action death, burial, compaction over geologic time leaching, runoff weathering combustion of fossil fuels Figure Page 856

14 Carbon in the Oceans  Most carbon in the ocean is dissolved carbonate and bicarbonate  Ocean currents carry dissolved carbon

15 Carbon in Atmosphere  Atmospheric carbon is mainly carbon dioxide  Carbon dioxide is added to atmosphere Aerobic respiration, volcanic action, burning fossil fuels Aerobic respiration, volcanic action, burning fossil fuels  Removed by photosynthesis

16 Nitrogen Cycle  Nitrogen is used in amino acids and nucleic acids  Main reservoir is nitrogen gas in the atmosphere

17 Nitrogen Cycle gaseous nitrogen (N 2 ) in atmosphere NO 3 - in soil nitrogen fixation by industry fertilizers NH 3 -,NH 4 + in soil 1. Nitrification leaching uptake by autotrophs excretion, death, decomposition uptake by autotrophs nitrogen fixation leaching ammonification2. Nitrification dentrification nitrogenous wastes, remains NO 2 - in soil food webs on land Figure Page 860

18 Nitrogen Fixation  Plants cannot use nitrogen gas  Nitrogen-fixing bacteria convert nitrogen gas into ammonia (NH 3 )  Ammonia and ammonium can be taken up by plants

19 Ammonification & Nitrification  Bacteria and fungi carry out ammonification conversion of nitrogenous wastes to ammonia conversion of nitrogenous wastes to ammonia  Nitrifying bacteria convert ammonium to nitrites and nitrates

20 Nitrogen Loss  Nitrogen is often a limiting factor in ecosystems  Nitrogen is lost from soils via leaching and runoff  Denitrifying bacteria convert nitrates and nitrites to nitrogen gas

21 Human Effects  Humans increase rate of nitrogen loss by clearing forests and grasslands  Humans increase nitrogen in water and air by using fertilizers and by burning fossil fuels  Too much or too little nitrogen can compromise plant health

22 guano fertilizer terrestrial rocks land food webs dissolved in seawater marine food webs marine sediments excretion weathering mining agriculture uptake by producers death, decomposition sedimentation settling out leaching, runoff weathering uplifting over geologic time dissolved in soil water, lakes, rivers uptake by autotrophs death, decomposition Phosphorus cycle Fig , p.862

23 Phosphorus Cycle  Phosphorus is part of phospholipids and all nucleotides  It is the most prevalent limiting factor in ecosystems  Main reservoir is Earth’s crust; no gaseous phase

24 Phosphorus Cycle GUANO FERTILIZER TERRESTRIAL ROCKS LAND FOOD WEBS DISSOLVED IN OCEAN WATER MARINE FOOD WEBS MARINE SEDIMENTS excretion weathering mining agriculture uptake by autotrophs death, decomposition sedimentation settling out leaching, runoff weathering uplifting over geologic time DISSOLVED IN SOILWATER, LAKES, RIVERS uptake by autotrophs death, decomposition Figure 47-27, Page 862

25 Human Effects  In tropical countries, clearing lands for agriculture may deplete phosphorus- poor soils  In developed countries, phosphorus runoff is causing eutrophication of waterways


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