Nutrient Cycles in Ecosystems

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 herbivores, carnivores, parasites primary producers detritivores, decomposers Fig. 47-14, p.852

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

5. Hydrologic Cycle Atmosphere precipitation onto land 111,000 wind-driven water vapor 40,000 evaporation from land plants (evapotranspiration) 71,000 evaporation from ocean 425,000 precipitation into ocean 385,000 surface and groundwater flow 40,000 Land Ocean Figure 47-15 Page 853

6. TRANSPIRATION EVAPORATION PRECIPITATION interception by plants dripping, trickling down along stems falling through to ground surface pooling, etc. overland flow infiltration of soil moisture in soil lateral flow seepage, percolation groundwater storage base flow DEEP OUTFLOW STREAM OUTFLOW Fig. 47-16, 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. 47-18, 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 47-19  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. diffusion between atmosphere and ocean Carbon Cycle - Marine combustion of fossil fuels bicarbonate and carbonate in ocean water aerobic respiration photosynthesis marine food webs death, sedimentation incorporation into sediments uplifting sedimentation marine sediments Figure 47-20  Page 856

13. Carbon Cycle - Land atmosphere combustion of fossil fuels volcanic action aerobic respiration combustion of wood photosynthesis terrestrial rocks sedimentation weathering land food webs soil water peat, fossil fuels death, burial, compaction over geologic time leaching, runoff Figure 47-20  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 • 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 (N2) in atmosphere nitrogen fixation by industry food webs on land uptake by autotrophs excretion, death, decomposition uptake by autotrophs fertilizers nitrogenous wastes, remains NO3- in soil nitrogen fixation dentrification ammonification 2. Nitrification NH3-,NH4+ in soil NO2- in soil 1. Nitrification leaching leaching Figure 47-25 Page 860

18. Nitrogen Fixation • Plants cannot use nitrogen gas • Nitrogen-fixing bacteria convert nitrogen gas into ammonia (NH3) • Ammonia and ammonium can be taken up by plants

19. Ammonification & Nitrification • Bacteria and fungi carry out ammonification • 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. mining fertilizer guano excretion agriculture uptake by autotrophs uptake by producers weathering leaching, runoff dissolved in soil water, lakes, rivers land food webs marine food webs dissolved in seawater death, decomposition death, decomposition sedimentation settling out weathering uplifting over geologic time terrestrial rocks marine sediments Phosphorus cycle Fig. 47-27, 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. mining FERTILIZER GUANO excretion agriculture uptake by autotrophs weathering uptake by autotrophs weathering MARINE FOOD WEBS DISSOLVED IN OCEAN WATER DISSOLVED IN SOILWATER, LAKES, RIVERS LAND FOOD WEBS death, decomposition death, decomposition settling out leaching, runoff sedimentation uplifting over geologic time TERRESTRIAL ROCKS MARINE SEDIMENTS Phosphorus Cycle 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