Lecture14_Ecosystems - Announcements Office Hours Dr Rypien Office hours after today will be by appointment only Last Time • Is nitrogen the

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Unformatted text preview: Announcements Office Hours - Dr. Rypien Office hours after today will be by appointment only Last Time: • Is nitrogen the limiting resource for this plant? - Law of the Minimum: growth is controlled not by the total resources available, but by the scarcest resource (limiting nutrient) Coral Aquarium Volunteer Needed 4 - 6 hours per week (SIO campus) Please email resume & experience to [email protected] N is limiting P is limiting N is limiting Tuesday, November 17, 2009 1 Tuesday, November 17, 2009 2 Last Time: Treatment Light, No Water Final Biomass (g) 1.46g Why?? no water ! no germination Maybe some dehydration explains slight weight loss water ! germination light ! photosynthesis CO2 from air incorporated into glucose through PS, so weight increased water ! germination Dark ! no photosynthesis Respiration leads to loss of matter (weight) that was stored in the seeds Mount St. Helens • - What is the ultimate source of energy for all consumers? - How does the movement of matter (carbon) differ? Mountain Lion Respiration Predation Decomposers Elk Herbivory Grass Photosynthesis With your neighbor : Compare your model of energy cycling Light, Water 1.83g Dark, Water 1.17g Energy Loss due to respiration (heat) Photosynthesis CO2 + H2O (+ energy) → glucose (C6H12O6) + O2 Respiration Glucose (C6H12O6) + O2 → CO2 + H2O (+ energy) Tuesday, November 17, 2009 3 Tuesday, November 17, 2009 4 How have humans impacted nutrient cycles? Objectives 1. Describe factors that influence cycling rates of nitrogen and carbon 2. Describe 3 ways human activities have influenced nutrient cycling 3. Extend ecosystem-level models of carbon movement to global models of whole earth carbon cycling Why is the world green? • Despite the limits to primary productivity, we still live in a green world - With your neighbor: What limits herbivore abundance? Predators Tuesday, November 17, 2009 5 Tuesday, November 17, 2009 No predators 6 !" Nutrient (Matter) Cycles Nitrogen Cycle • • Energy flows, matter cycles • • • • - Matter = Nutrients (Carbon, nitrogen, phosphorus, etc.) Nutrient (re)cycling is critical for ecosystems Where do we find N in living tissue? - Amino acids, nucleic acids - Important for photosynthesis (Rubisco & chlorophyll) - Biogeochemical cycles N is abundant (80% of atmosphere) N fixation by bacteria Decomposition Tuesday, November 17, 2009 7 Tuesday, November 17, 2009 8 .4 20 (days) orous aterpillar unonia J c ent(*-) and elevated m Fajer et al. (1989), ree means + 1 SE. as been altered at least es different questions. crease in nitrogen fixe in nitrous oxide that ded nitrogen retained arbon storage (Melillo r is the anthropogenal ecosystems by other thways could include en oxides, which can spheric ozone (Logan ia, which alters other stry (Schlesinger and aquatic systems, which r and Rabelais 1991); would be benign. possible effects of N ms (resulting from the ation of N upwind) on , and trace gas emisb 100number of forest eco0~ c er et al. 1991, Bowden x here is some evidence z issions of N-contain·cD 50 arbon storage in such 0 ce that forest dieback be caused, at least in sition (Schulze 1989). 1920 1940 1960 1980 istry of the nitrogen cts on ecological proYear levels. Nummunity Tuesday, November 17, 2009 FIG. 8. Extent of human alterationof the global biogeosing fertilization with N chemicalcycle of nitrogen.The "natural fixation"line repthe many ecosystems resentsbiologicalN fixationin naturalterrestrial ystemsplus s production, added ni- fixationby lightning; assumethat naturalbiologicalfixation I f dominance into one has not changedrecently,althoughit probablyhas declined t species (Tilman 1987, due to land use changeand increasedN deposition.The "anN t thropogenic fixation"line represents he sum of industrial nneke et al. 1990). Net N fixation for fertilizers,fixation during fossil fuel combuss are increased by the tion, and fixationby leguminouscrops (Smil 1991, Vitousek ll species richness is and Matson 1993). Nitrogenbiogeochemistry: he changereT ports the modem fractionsfor each source. ig. 10). to infertile soils have declined (Heil and Diemont 1983, Bobbink et al. 1988, Bobbink 1991). Overall, there has been a substantial decrease in within-community diversity (Bobbink and Willems 1987, Berendse and Elberse 1990). Diversity among communities may have decreased as well, because atmospheric N deposition increases nutrient availability in sites that formerly were infertile, and thereby favors the growth of nitrogendemanding species everywhere. At present, western and central Europe are most strongly affected by excess N deposition. However, substantial areas in North America also receive anthropogenic N, and most of the recent growth in the use of N fertilizer is in the tropics (Vitousek and Matson 1993). Additions of nitrogen can be expected to affect consumers, decomposers, and symbionts as well as plants. Increases in nitrogen concentrations in plant tissue favor the growth and survival of many consumers (the converse of the effects of elevated CO2 discussed above) (Mattson 1980, Field et al. 1992) and can affect populations of predators and parasites as well (Loader and Damman 1991). The tissue produced by N-fertilized Nitrogen Cycle Nitrogen Cycle • • Human impacts ! The Green Revolution Plant growth is limited by nitrogen in the atmosphere available to plants of fertilizer • • What happens to fertilizer when it enters aquatic systems? Eutrophication = increased nutrients - Bacterial nitrogen fixation makes the huge amount of N2 - Haber-Bosch process: Synthetic N2 fixation & production - Respiration & bacterial decomposition: Organic compounds (glucose) + O2 → CO2 + H2O - Increased phytoplankton growth (and death) - Reduced oxygen concentration - hypoxia kills fish & other organisms (Dead zones) 9 Tuesday, November 17, 2009 10 Nitrogen Cycle Carbon Cycle • Too much N (e.g., agricultural fertilizer) can lead to the formation of dead zones - Example: Gulf of Mississippi • • • Photosynthesis Respiration Human imbalance Summer Winter Tuesday, November 17, 2009 11 Tuesday, November 17, 2009 12 Carbon Cycle Carbon Cycle • In your notebook: Draw a graph that predicts the daily gross primary productivity (photosynthesis) over 365 days for a deciduous forest in Alaska • How does carbon cycle in the Mount St. Helens ecosystem? - What is the ultimate source of matter for all consumers? Mountain Lion Predation Decomposers Elk Herbivory Respiration Grass Photosynthesis Atmosphere (CO2) Respiration - Add a second line to show rates of respiration over the same time period Photosynthesis Tuesday, November 17, 2009 13 Tuesday, November 17, 2009 14 CQ Which of the following has the greatest effect on the rate of nutrient cycling in an ecosystem? A. Rate of primary productivity B. Trophic efficiency C. Location of nutrient reservoirs D. Rate of decomposition E. Amount of sunlight Decomposition • • Decomposers (bacteria, fungi, nematodes, etc.) are critical for recycling nutrients in ecosystems What environmental factors limit decomposition? - Temperature - H2O - Nutrient availability Tuesday, November 17, 2009 15 Tuesday, November 17, 2009 16 Carbon Cycle Keeling Curve • Why do we care about carbon? - Primary production supports biological systems - Foundational to life - Changing global carbon cycle • Tuesday, November 17, 2009 17 http://www.esrl.noaa.gov/gmd/ccgg/trends/ 18 Tuesday, November 17, 2009 Keeling Curve Global Carbon Models • N. Hemisphere Winter Carbon resides in pools - Pools can be sources or sinks • Fluxes show directional movement of carbon between pool flux Pool 1 e.g. plant flux Pool 2 e.g. atmosphere N. Hemisphere Summer Source (C out) net flux Sink (C in) Tuesday, November 17, 2009 19 Tuesday, November 17, 2009 20 Global Carbon Models respiration Atmosphere photosynthesis consumption Global Carbon Models • For carbon, source/sink is relative to a pool’s interaction with the atmosphere Secondary Consumers (Carnivores, omnivores) - What are the major carbon pools? Atmosphere Ocean Soil Plants Animals consumption Primary Consumers (Herbivores) consumption Primary Producers (Plants, algae) consumption (Fungi, bacteria, worms) - What are the net fluxes? Source (C out) net flux Sink (C in) Decomposers Tuesday, November 17, 2009 21 Tuesday, November 17, 2009 22 CQ Global Carbon Models Rainforest 1 Rainforest 2 acts as a: acts as a: A. B. C. D. Source Sink Source Sink Source Sink Sink Source Rainforest 1 Petagram = 1015 gram Rainforest 2 Tuesday, November 17, 2009 23 Tuesday, November 17, 2009 24 Global Carbon Cycle • Humans have changed the amount of greenhouse gas (CO2, methane) in the atmosphere Tuesday, November 17, 2009 25 Tuesday, November 17, 2009 26 CQ Carbon Sequestration Carbon Sequestration • • Residence (turnover) time • - Approximate time carbon is “held” in a pool before moving to the next Which pool in the global carbon cycle has the greatest potential for sequestering carbon? A. Atmosphere B. Land Plants C. Soil D. Ocean Pool Atmosphere Land Plants Soil Ocean Pool size Avg. Residence (billions of tons) Time (years) 750 3 610 1580 39000 5 25 350 Carbon sequestration - Carbon that is not actively cycling back to the atmosphere as CO2 Pool Atmosphere Land Plants Soil Ocean Tuesday, November 17, 2009 Pool size (billions of tons) 750 610 1580 39000 Avg. Residence Time (years) 3 5 25 350 27 Tuesday, November 17, 2009 28 Carbon Sequestration Carbon Sequestration • Can we get the ocean to sequester more carbon? - How does carbon get into the ocean? • “Give me half a tanker of iron, and I’ll give you an ice age” • Dissolved CO2, photosynthesis - 12 iron addition experiments since 1993 - What is limiting NPP in the ocean? Colors indicate chlorophyll levels Tuesday, November 17, 2009 29 Tuesday, November 17, 2009 30 CQ Carbon Sequestration • The graphs show data from an iron addition experiment in the Southern Ocean. Did the addition of iron lead to a phytoplankton bloom? = Iron-Fertilized Waters = Control A. Yes B. No Carbon Sequestration • Why aren’t we dumping iron into the oceans everywhere? - Plankton bloom ≠ carbon sequestration • • Excess carbon does not enter deep waters Blooms can deplete other essential nutrients (O2, silica, etc.) Days of Experiment Tuesday, November 17, 2009 31 Tuesday, November 17, 2009 32 Global Carbon Cycle With your neighbor : Trace how a molecule of carbon could get from the tailpipe of my car to the tuna in my sandwich gasoline + O2 ! CO2 + H2O + heat Tuesday, November 17, 2009 33 ...
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This note was uploaded on 12/02/2009 for the course BILD BILD 3 taught by Professor Woodruff during the Fall '08 term at UCSD.

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