1. Lecture 10: Pathways of Elements in Ecosystems Huang He Phone: 18972127775 QQ:105367750 E-mail: hn.huanghe@163.com PPT 模板下载： www.1ppt.com/moban/ 行业 PPT 模板： www.1ppt.com/hangye/ 节日 PPT 模板： www.1ppt.com/jieri/ PPT 素材下载： www.1ppt.com/sucai/ PPT 背景图片： www.1ppt.com/beijing/ PPT 图表下载： www.1ppt.com/tubiao/ 优秀 PPT 下载： www.1ppt.com/xiazai/ PPT 教程： www.1ppt.com/powerpoint/ Word 教程： www.1ppt.com/word/ Excel 教程： www.1ppt.com/excel/ 资料下载： www.1ppt.com/ziliao/ PPT 课件下载： www.1ppt.com/kejian/ 范文下载： www.1ppt.com/fanwen/ 试卷下载： www.1ppt.com/shiti/ 教案下载： www.1ppt.com/jiaoan/ 2015-5-23 1

2. Burning of fossil fuels and forests has increased atmospheric CO2 concentrations from 280 ppm to 385 ppm since the Industrial Revolution. Understanding why and how ecosystem responses depends a basic understanding of carbon sources and sinks and processes involved. 2

3. College of Chemistry and Environmental EngineeringHuang He Outline : Biogeochemical cycles 10.1 Energy transformations and element cycling are intimately linked 10.2 Ecosystems can be modeled as a series of linked compartments 10.3 Water provided a physical model of element cycling in ecosystems 10.4 Carbon cycle is closely tied to the flux of energy through the biosphere 10.5 Nitrogen assumes many oxidation states in its cycling through ecosystems 10.6 Phosphorus cycle is chemically uncomplicated 10.7 Sulfur exists in many oxidized and reduced forms 10.8 Microorganisms assume diverse roles in element cycles 3

4. 10.1 Energy transformations and element cycling are intimately linked Assimilatoiry process: transformation of inorganic forms of elements into the molecules of organisms, such as photosynthesis Dissimilatory process: transformation of organic form of elements back to inorganic form, such as respiration. Chemical transformations of elements occurs in the soil, air, and water, with and without organisms involved (weathering, lightning) Biochemical transformation involves oxidation and reduction. 4

5. 10.2 Ecosystems can be modeled as a series of linked compartments Compartment models Carbon, Inorganic forms to organic forms Within each compartment, we can reorganize subcompartments Organic forms: animals, plants, microbes, detritus 5

6. 10.3 Water provides a physical model of element cycling in ecosystems Major processes involved in water cycling: evaporation, transpiration and precipitation Solar energy drives evaporation Condensation forms precipitation Unit in the chart: 10^18 g, teraton (a trillion metric tons) Biosphere: 1,400,000 97% in oceans Residence times: Air: 1/26 =2 weeks Earth surface: 2,800 yrs 6

7. 10.4 Carbon cycle is closely tied flux of energy Processes: 1.Photosynthesis and respiration 2.Ocean- atmosphere exchange 3.Precipitation of carbonates in aquatic systems 4.Methanogenesis in swamps, marshes wetlands Gigaton (10^15 g, billion metric ton) 7

8. College of Chemistry and Environmental EngineeringHuang He Carbon cycle Tightly linked to energy flow Difference between production and loss NPP=GPP-Ra Net ecosystem productivity NEP=GPP- Ra-Rh NEP=NPP-Rh Note storage Carbonates Coral reefs Limestone Coal Oil Gas Peat 8

9. College of Chemistry and Environmental EngineeringHuang He Global carbon cycle Carbon budget of Earth is closely linked to atmosphere, land and ocean and mass movement around planet. Unit in gigatons (Gt= 10^9 metric ton=10^15 g) Earth contains 10^23 g of C (100 m Gt ) 9

10. College of Chemistry and Environmental EngineeringHuang He Global Carbon Cycle 10

11. 4CH3OH (methanol)  CH4 + CO2 +2 H2O CH4 can absorb about 25 times as much as infrared radiation as one CO2. Cattle farm The global carbon cycle involves diverse biochemical and chemical transformations. 11

12. Atmospheric CO 2 concentration change 12

13. 10.5 Nitrogen assumes many oxidation states in its cycling through ecosystems Unit: 10^12 g N yr-1, GT N or GT N yr- 1 13

14. College of Chemistry and Environmental EngineeringHuang He Nitrogen cycle Nitrogen is essential to life Two uptake forms: Ammonium (NH4+) and nitrate (NO3-) Starts with nitrogen fixation from atmosphere Plants can only utilize nitrate or ammonia Atmospheric deposit Dryfall+wetfall Nitrogen fixation High energy (lightning, 0.4 kg N ha-1) in NH3 and HNO3 (nitric acid) Biological Bacteria, 10 kg N ha-1. 14

15. College of Chemistry and Environmental EngineeringHuang He N fixation: N2 is converted into NH3 (NH4+ then ) by bacteria. Ammonization: a process that organic N is converted to NH4+ Nitrification: a process that NH4+ is oxidized to NO2- and to NO3- Denitrification: under anaerobic condition, NO3- is reduced to N2O and N2 and returned to atmosphere. 15

16. Nitrogen assumes several different oxidation states as it cycles through ecosystems 16

17. Nitrogen movement after fertilization in forests 17

18. College of Chemistry and Environmental EngineeringHuang He Global nitrogen cycle Unit: 10^12 g N yr- 1 3.9x 10^9 120 x 10^3 3.5 x 10^3 NxO Nitrous oxide (N2O) Nitric oxide (NO) Nitrogen oxide (NO2) 18

19. 10.6 The phosphorus cycle is chemically uncomplicated Phosphorus does not enter the atmosphere in any form other than dust, so little phosphorus cycles between the atmosphere and other compartments of ecosystems 19

20. College of Chemistry and Environmental EngineeringHuang He No atmospheric reservoir (rock and natural phosphate deposits) Follow water path, permanent loss of phosphorus to oceans Input limited to weathering of rocks Terrestrial systems can be limited by phosphorus availability (natural ecosystems) Phosphorus is more abundant in marine and freshwater systems Particulate organic P (contained in bacteria, algae, detritus) Dissolved organic phosphorus  Rapidly utilized by zooplankton  Secrete inorganic Dissolved inorganic phosphorus Rapidly utilized by phytoplankton Phosphorus can sink as particulate phosphorus and become locked in bottom sediment Depletion of surface layers, only return due to upwelling Phosphorus cycle has no atmospheric pool 20

21. College of Chemistry and Environmental EngineeringHuang He Phosphorus cycle has no atmospheric pool 21

22. College of Chemistry and Environmental EngineeringHuang He Global phosphorus cycle Unit 10^12 g P yr-1 22

23. 10.7 Sulfur exists in many oxidized and reduced forms cycle 23

24. College of Chemistry and Environmental EngineeringHuang He Sulfur cycle is both sedimentary and gaseous (hybrid) Hydrogen sulfide (H2S) Sulfur dioxide (SO2) Sulfuric acid (H2SO4) 24

25. College of Chemistry and Environmental EngineeringHuang He Global sulfur cycle (poorly understood) Unit: 10^12 g S yr-1 25

26. College of Chemistry and Environmental EngineeringHuang He 10.8 Microorganisms assume diverse roles in element cycles Heterotrophs: obtain carbon in reduced ( organic) form by consuming other organisms or organic detritus. All animals and fungi, and many bacteria, are heterotrophs. Autotrophs assimilate carbon as carbon dioxide and expend energy to reduce it to an organic form. Photoautotrophs use sunlight as their source of energy for this reaction ( photosynthesis). All green plants and algae are photoautotrophs, as are cyanobacteria. All of these organisms use H2O as an electron donor ( reducing agent) and are aerobic. Purple and green bacteria are also autotrophs, but their light- absorbing pigments differ from those of green plants, they use H2S or organic compounds as electron donors, and they are anaerobic. 26

27. College of Chemistry and Environmental EngineeringHuang He Microorganisms assume diverse roles in element cycles Chemoautotrophs use CO2 as a carbon source, but they obtain energy for its reduction by the aerobic oxidation of inorganic substrates: methane ( for example, Methanosomonas and Methylomonas); hydrogen ( Hydro- genomonas and Micrococcus); ammonia ( the nitrifying bacteria Nitrosomonas and Nitrosococcus); nitrite ( the nitrifying bacteria Nitrobacter and Nitrococcus); hydrogen sulfide, sulfur, and sulfite ( Thiobacillus); or ferrous iron ( Ferrobacillus and Gallionella). Chemoautotrophs are almost exclusively bacteria, which are apparently the only organisms that can become specialized biochemically to make efficient use of inorganic substrates in this way and dispose of the resulting waste products. 27

28. Bacteria use oxygen from seawater to oxidize the hydrogen sulfide in vent water ( H2S  SO42 + energy), which provides them with a source of energy for the assimilatory reduction of inorganic carbon and nitrogen from seawater ( e. g., NO3  NH4+). Chemoautotrophic sulfur bacteria form the base of the food chain in hydrothermal vent communities. Other vent organisms, such as these tubeworms ( Riftia pachyptila) at a Pacific hydrothermal vent, rely on these bacteria to produce food. 28

29. The cycling pathways of carbon and phosphorus differ in temperate lakes. 29

30. 30

31. College of Chemistry and Environmental EngineeringHuang He 10.9 Two major types of biogeochemical cycles All nutrients follow biogeochemical cycles Two major types of cycle Gaseous  Major reservoirs are atmosphere and oceans  Global in nature, important gases – Oxygen 21% – Nitrogen 78% – Carbon of carbon dioxide 0.03% Sedimentary  Major reservoirs are soil, rocks and minerals  Rock phase and salt solution phase  Salt solution is the available form – Phosphorus – Metals, eg Calcium, Magnesium, etc Some cycles are hybrid Sulfur (S) Major pools in Earth’s crust and atmosphere 31

32. College of Chemistry and Environmental EngineeringHuang He Two major types of biogeochemical cycles Common features: Involve biological and non-biological processes Driven by the flow of energy through ecosystem Tied to water cycle (water is the important medium; Without water cycle, biogeochemical cycle would cease). Share three basic components: inputs, internal cycling outputs. 32

33. College of Chemistry and Environmental EngineeringHuang He 10.10 Inputs and outputs Nutrients enter the ecosystem via inputs Gaseous cycle from atmosphere (C,N) Sedimentary from rocks and minerals (P, Ca) Wetfall and dryfall Precipitation -- wetfall Airborne particular and arsenal (rainfall on the forest floor is nutrient rich than on the bare soil) -- dryfall Nutrient in aquatic ecosystem From surround lands in the form of drainage water, detritus, sediment and precipitation. 33

34. College of Chemistry and Environmental EngineeringHuang He Outputs There are also outputs to the biogeochemical cycles Carbon to carbon dioxide, release back to atmosphere Nutrient to gaseous form (denitrification) Loss of organic matter from ecosystem by washout (from terrestrial to aquatic) Herbivores between aquatic and terrestrial  Moose (feed on aquatic plants, deposit nutrient in terrestrial ecosystem in the form of feces)  Hippopotamus (move organic matter from terrestrial to aquatic) Harvesting may be replaced by fertilization Loss of nutrient (e.g.Leaching) may be balanced by inputs (weathering of rocks and minerals) 34

35. College of Chemistry and Environmental EngineeringHuang He Internal cycling Nutrients are recycled within the ecosystem Internal recycling is important within ecosystem Some systems have large amount of short term recycling  Lakes Other have most stored as biomass  Forests Long term storage in water systems is in the sediment 35

36. College of Chemistry and Environmental EngineeringHuang He A generalized biogeochemical cycle Note input, internal cycling, and output 36

37. College of Chemistry and Environmental EngineeringHuang He Pools and fluxes Three calcium pools: Plants, dead OM and soil Pool size: 290, 140, 440 kg ha-1 Fluxes (kg ha-1 yr-1) F1: uptake F2: litterfall F3:leaching from plants F4:net mineralization Turnover time: t=P/f steady-state t_p=4.8, t_OM=2.3, t_s=7.3 (years) 37

38. College of Chemistry and Environmental EngineeringHuang He 10.11 Various biogeochemical cycles are linked All elements are components of living organisms and constituents of organic matter Thus all cycles are linked: Chemically Energetically Biologically Stoichiometry: quantitative relationship of elements in combination. Example: C:N ratio, 8 to 15 for microbes, 30 for leaf, etc C:N:P ratio 38

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