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Communities and Ecosystems

Communities and Ecosystems. Energy, nutrients, and interactions. External energy source, usually solar energy but also chemical energy. Figure 54-1. Primary producers (autotrophs) Organisms that can synthesize their own food. Abiotic environment The soil, climate, atmosphere,

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Communities and Ecosystems

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  1. Communities and Ecosystems Energy, nutrients, and interactions

  2. External energy source, usually solar energy but also chemical energy Figure 54-1 Primary producers (autotrophs) Organisms that can synthesize their own food Abiotic environment The soil, climate, atmosphere, and the particulate matter and solutes in water Consumers Organisms that eat other living organisms Decomposer Organisms that feed on dead organisms or their waste products

  3. Net primary productivity (kgC/m2/year) 3 Figure 54-2 2 1 0

  4. Barrow Figure 50-9 Dawson Chicago Konza Prairie Yuma Belém

  5. Area covered, by ecosystem type NPP per unit area Total NPP Figure 54-3 Aquatic Terrestrial

  6. Energy source: 1,254,000 kcal/m2/year 0.8% energy captured by photosynthesis. Of this… Figure 54-8 … 55% is lost to maintenance activities or as heat … 45% supports growth (Net primary production) … 34% enters decomposer food web as dead material …11% enters consumer food web

  7. Energy flow and biomass accumulation; the concept of a “pyramid of numbers” Figure 54-7 Production of biomass (g/m2/year) 3 Tertiary consumers 10% Efficiency of energy transfer Secondary consumers 30 15% 20% Primary consumers and decomposers 200 Primary producers 1000

  8. But not all pyramids are the same – Why?

  9. THE GLOBAL WATER CYCLE All values in 1018 grams per year Net movement of water vapor by wind: 36 Figure 54-13 Precipitation over ocean: 283 Evaporation, transpiration: 59 Evaporation from ocean: 319 Precipitation over land: 95 Percolation Runoff and groundwater: 36 Water table (saturated soil)

  10. Air rises over mountains and cools; rain falls Figure 50-26 East Dry air creates desert conditions West Moisture-laden air blows onshore from Pacific Ocean Cascade Mountains This area is in a rain shadow

  11. THE GLOBAL CARBON CYCLE All values in gigatons of carbon per year Atmosphere: 778 (during 1990s) Figure 54-14 Net uptake via photosynthesis by plants: 3.0 Land-use change (primarily deforestation): 1.6 Net uptake via photosynthesis, chemical processes: 1.5 Fossil-fuel use: 6.3 Organisms, soil, litter, peat: 2190 Rivers (erosion): 0.8 Organisms, chemical processes in ocean: 40,000 Terrestrial ecosystems Aquatic ecosystems Human-induced changes

  12. Global changes in atmospheric CO2 over time Figure 54-15c

  13. Cold-water copepods are declining in the North Atlantic. Figure 54-19a Great Britain Warm-water copepods Cold-water copepods

  14. Much of the ocean is stratified by density and temperature. Figure 54-21a Surface layer: Water is warm, less dense Nutrient-rich water is brought to the surface by currents Density gradient Benthic zone: Water is 4°C, highest density

  15. Global warming increases the density gradient, making it less likely for layers to mix. Figure 54-21b Surface layer: Water is much warmer, less dense Currents are less likely to bring nutrient-rich water to surface, against the steeper density gradient Much steeper density gradient Benthic zone: Water is 4°C, highest density

  16. THE GLOBAL NITROGEN CYCLE All values in gigatons of nitrogen per year Figure 54-16 Atmospheric nitrogen (N2) Industrial fixation: 100 Protein and nucleic acid synthesis Bacteria in mud use N-containing molecules as energy sources, excrete N2: 310 Lightning and rain: 3 Internal cycling: 1200 Nitrogen-fixing bacteria in roots and soil: 202 Nitrogen-fixing cyanobacteria: 15 Internal cycling: 8000 Runoff: 36 Decomposition of detritus into ammonia Mud Permanent burial: 10

  17. Figure 31-1 Without With normal mycorrhizal fungi

  18. Lightning Fossil fuels Figure 54-17 Nitrogen- fixing crops Biological fixation Nitrogen fertilizer

  19. Root nodules Figure 28-6

  20. Eutrophication from excess fertilizing in Lake 226, Manitoba – But not from nitrogen!

  21. NITRATES AS A POLLUTANT 1.Ammonia (NH3) is introduced as fertilizer. NH3 2.Corn uses ammonia (NH3) to build protein. Soil-dwelling bacteria and archaea use NH3 as an electron donor during cellular respiration. Figure 28-7 Cellular respiration 3.Nitrate (NO3–) is a by-product of respiration. Nitrate percolates into groundwater, causing contamination, or runs off fields into rivers. NO3– (enters groundwater) N2 4.Nitrate from rivers is used by marine algae and cyanobacteria to build proteins (on right); or it is used as an electron acceptor by bacteria (on left). Huge populations bloom because of increased nitrogen supply. Nitrogen (N2), a by-product of respiration, goes into the atmosphere. NO3– 5. When cells that bloomed eventually die, decomposing bacteria and archaea grow rapidly, using up O2. 6. ANOXIC “DEAD ZONE”

  22. Acid precipitation (from N, and S as well…)“Too acid” is ≤ 5.6

  23. Disturbance, and recovery of systems after disturbances Giant sequoias after a fire Fire scars in the growth rings Figure 53-20 Reconstructing history from fire scars

  24. Old field Figure 53-21-1 Disturbance (plowing) ends, site is invaded by short-lived weedy species. Pioneering species

  25. Weedy species are replaced by longer-lived herbaceous species and grasses. Early successional community Figure 53-21-2 Shrubs and short-lived trees begin to invade. Mid-successional community

  26. Short-lived tree species mature; long-lived trees begin to invade. Late-successional community Figure 53-21-3 Long-lived tree species mature. Climax community

  27. Soils exposed 45–80 years: Sitka adler, scattered cottonwood Soils exposed 20 years or less: willow, Dryas Soils exposed 100 years: Sitka alder, scattered spruce Soils exposed 150–200 years: dense Sitka spruce, western hemlock Figure 53-22 This glacier once reached the sea, then exposed sediments as it retreated up the “bay” Alaska Direction of glacial retreat

  28. Competition as a structuring force… Chthamalus in upper intertidal zone Figure 53-5 Mean tide level Semibalanus in lower intertidal zone

  29. Figure 53-6-competitive-exclusi

  30. Figure 53-6-competitive-exclusi

  31. Warning! The caption-questions for this figure (blue text) are: (#1) Useful to try (#2) Confusingly worded; if you are trying the second one, think carefully. Figure 53-6-competitive-exclusi

  32. The niche principle Whencompetition is asymmetric and niches do not overlap completely, weaker competitors use nonoverlapping resources. Figure 53-4d Species 1 (strong competitor) Species 2 (weak competitor) Fundamental niche Realized niche Or, range of conditions which may be tolerated)

  33. Other prey include: barnacles, limpets, other snail spp., clams, crabs, etc., 18-20 species altogether Predation as a structuring force… Predator: Pisaster ochraceous Figure 53-18 Prey: Mytilus californianus (main one!)

  34. P. ochraceous (keystone predator) present Figure 53-19

  35. P. ochraceous (keystone predator) present Figure 53-19 P. ochraceous (keystone predator) absent

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