ENVSCI 260 Global Environmental Change: Carbon Storage
Questions:
Answer each of the following questions. Each question is worth 2 pts.
Global Forests and carbon storage
1) Global forests are considered a sink for atmospheric carbon because large trees can sequester carbon as they grow and hold the carbon in woody biomass (i.e. the mass of the tree itself) for centuries.
- What are the two potential pathways for the carbon stored in trees after they die? Which of these pathways would lead to long-term carbon burial? Describe or illustrate this process.
- A recent study in the journal Science(http://science.sciencemag.org/content/early/2017/09/27/science.aam5962) challenges this long-held view (at least for tropical forests) stating the deforestation is causing tropical forested land to act as a source of carbon to the atmosphere instead of a sink. Describe how the process of deforestation shifts the potential pathways for carbon described in part A.
2) A recent study in Global Change Biology (Kautz et al., Glob. Change Biol. 2018, 24:2079-92) investigated the effects of insects, disease, and forest fires on the U.S. forest carbon reservoir. They found that insects and disease cause a net loss (or flux out of the forest reservoir) of 13.2 Mt C/yr and forest fires cause a net loss of 7.8 Mt C/yr. The U.S. carbon reservoir is approximately 8.7 Gt C.
- Draw a diagram of the reservoir of carbon in U.S. forests with the outflow caused by insects, disease, and wildfires.
- Climate change is expected to increase both insect infestations and wildfires. What would the carbon flux out of the forest reservoir be in 2040 if these processes doubled over the next 20 years?
- If this doubling occurs, would the system be at steady state? Why or why not? What would you expect to happen to the forest reservoir overtime?
3) The warming of artic regions in Alaska, Greenland, and Siberia have the potential to expand boreal forests which currently have a carbon reservoir of 272 Gt C. As the boreal forest expands, inflow into the forest increases as outflow remains the same.
- What is the overall effect on the size of the boreal forest carbon reservoir as the boreal forest expands?
- If the boreal forest doubled in size over the next 50 years, what would the net flux of carbon from the atmosphere need to be to increase the boreal forest carbon reservoir by 272 G ton C (in Gt C/yr)? (Assume an average flux over the 50 years)
Extra credit: The warming of the artic regions affects planetary energy balance in a number of ways. The expansion of the forests increases carbon sequestration as described above, but it also impacts albedo. Explain how albedo might be affected by the expansion of the boreal forests in the Artic. Taking into account the additional carbon sequestered and the changes in albedo, what do you think the overall impact of the expansion of the boreal forests would be on Earth’s climate? Justify your answer.
Planetary Energy Balance of our Neighbor Planets
4) Venus is 67 million miles from the sun compared with Mercury which is 36 million miles from the sun. How much more solar flux does Mercury receive relative to Venus?
5) The average surface temperature of Mercury is 440 K (167o C), while the average surface temperature of Venus is 735 K (462o C).
- How well does the solar flux received by each of these planets explain the actual surface temperature of these planets? Explain your answer.
- What are the other factors that affect planetary energy balance? Which of these factors are responsible for the higher temperature on Venus relative to Mercury?
6.) Observations of the Martian surface strongly suggest that Mars once had a much warmer climate with liquid water. Because there is no reason to believe that solar radiation and surface albedo has changed drastically since the formation of the planet, warming must be attributed to an early greenhouse effect. To explain the hypothesis of an early warm Mars, scientists have attempted to reconstruct the composition of the early Martian atmosphere. Carbon dioxide and water vapor are two greenhouse gases that are believed to have played a large role in the early greenhouse effect on Mars.
- Describe the absorption spectrum for these two gases and how this relates to the greenhouse effect.
- What are the molecular properties of these molecules that allow them to absorb radiation at these wavelengths?
Nitrogen Cycle. In the Midwest, agricultural run-off is often high in nitrogen and being able to reduce nitrogen loading through natural processes such as denitrification can help to reduce eutrophication and hypoxic conditions. A 2006 study by David et al. (Ecol Appl. 16:2177-90) investigated the role that Lake Shelbyville, Illinois, played in reducing nitrogen loading to rivers within the Mississippi River watershed. They found that the influx of nitrogen from agricultural run-off was 9000 Mg N/ yr, while the average denitrification rate was 5200 Mg N/ yr.
7) What is the difference between the nitrogen inputs and denitrification rate in Lake Shelbyville? This is the amount of Nitrogen that leaves Lake Shelbyville and is exported to nearby rivers. Draw a diagram with Lake Shelbyville as the nitrogen reservoir and all the inputs and outputs from the reservoir.
8) The residence time for nitrogen in Lake Shelbyville is 0.40 years. What is the total size of the nitrogen reservoir in Lake Shelbyville (assuming that it is at steady-state)?
Answers:
Global Forests and carbon storage
1.
a. The two potential pathways for the carbon storage in trees after they die is firstly the plants do not respire and the carbon stored in the plants gets locked. The second pathway is when plants die the tress gets buried in the soil, the microbes that act on the tree and decompose releases carbon in to the soil (Cavanaugh et al., 2014).The wood burial or the storage of carbon in the soil particle from the decomposing wood is a long term option of carbon burial. To describe this process, it is important to highlight that the forest acts as natural sink for atmospheric carbon. The photosynthetic activity performed by the plants leads to the storage of carbon into the plant cells. while this stored carbon again returns to the atmosphere through the respiration in plants. Thus, after a plant dies the carbon stored in trees is locked and wood gets buried in soil. The buried wood is then decomposed the soil microbes, carbon is released into the soil and gets stored for a longer period (Seto, Güneralp & Hutyra, 2012).
b. Forests take up carbon dioxide through the process of photosynthesis and the carbon is utilized in the biomass creation through the process of primary productivity. The carbon is then stored within the plant cells and a part of it released into the atmosphere through the deforestation, and decomposition. Carbon is stored within the old trees, top six inches of the soil and after a trees dies, the stored carbon is slowly released in to the atmosphere (Baccini et al., 2012).
2.
a.
Figure 1: Carbon flux (done by author)
b. The carbon flux out of the reservoir in the year 2040 will be 26.4 Mt C/year in case of out fluxes due to the insects and diseases. The out fluxes from the reservoir will be 15.6 Mt C/year in the year 2040 (Keenan et al., 2014).
c. Even if the doubling occurs after a period of 20 years, the system will still be at steady state because the incidence of the diseases and insects on the forest reserve will be natural process, the same will true for the forest which majorly occur due to natural reasons. The forest reservoir on the long run will reduce in reduce in quantity (Keenan et al., 2014).
3.
a. Considering the fact that the boreal forests is expanding, the overall effect on the size of the boreal forest will also expand geographically and the carbon reservoir will increase to 400 Gt C (Oechel et al., 2014).b. If the size of the boreal forests is doubled over 50 years then the additional increase in the net flux of atmospheric carbon will be 1.3 Gt C/year (Oechel et al., 2014).
Extra credit: considering the increased spread of the boreal forests in to the artic regions, there will be increased heating effect of the atmosphere initially. However, as the time will progress the boreal forest will utilize sunlight to process increased photosynthetic activity. The increased carbon sequestration will reduce the atmospheric temperature (Oechel et al., 2014).
Planetary Energy Balance of our Neighbor Planets
4.
Solar flux received by Venus is 662 W/m2 and the solar flux received by Mercury is 2290 W/m2. Thus, Mercury receives 1628 W/m2 solar flux more than Venus (Welsh et al., 2012).
5.
a. The solar flux received by Mercury is much higher than the solar flux received by Venus. However, the factors of planetary energy balance affect the actual temperature of the planets (Wild et al., 2013).b. the factors that affect the planetary energy balance is the distance of the planet from the sun, greenhouse effect and albedo. The factors that are responsible for the higher temperature on Venus in comparison to Mercury is albedo and greenhouse effect (Wild et al., 2013).
6.
a. The absorption spectrum of water vapour is wide ranging and it includes the ultraviolet radiations (<200 nm), infrared radiation (1 micron to 10 micron), far infrared (10 micrometre- 1 nanometre) and microwave (1 mm-10 cm). The absorption spectrum of water is very complex (Tahir & Amin, 2013).The absorption spectrum of carbon dioxide includes infrared radiation in three different wavelengths of 2.7 micrometre, 4.3 micrometre and 15 micrometres. Thus, it is important to mention that both water vapour and carbon dioxide are potent absorbers of infrared radiation (Tahir & Amin, 2013).
b. The chemical structure and the bonding are the vital properties that render the molecules absorb the infrared radiation (Yu, Huang & Tan, 2012).
Nitrogen Cycle
7.
The nitrogen inputs here mean the rate at which the nitrogenous materials enter into the Lake Shelbyville per year. While, the denitrification rates mean the rate at which the nitrate is reduced and molecular nitrogen is produced (Bonnett et al., 2013).
Figure 2: Nitrogen reservoir (done by author)
8.
The total size of the nitrogen reservoir in the Lake Shelbyville is 3600 mg N/year (web.viu.ca., 2018).
References
Baccini, A. G. S. J., Goetz, S. J., Walker, W. S., Laporte, N. T., Sun, M., Sulla-Menashe, D., ... & Samanta, S. (2012). Estimated carbon dioxide emissions from tropical deforestation improved by carbon-density maps. Nature climate change, 2(3), 182.
Bonnett, S. A. F., Blackwell, M. S. A., Leah, R., Cook, V., O'connor, M., & Maltby, E. (2013). Temperature response of denitrification rate and greenhouse gas production in agricultural river marginal wetland soils. Geobiology, 11(3), 252-267.
Cavanaugh, K. C., Gosnell, J. S., Davis, S. L., Ahumada, J., Boundja, P., Clark, D. B., ... & Sheil, D. (2014). Carbon storage in tropical forests correlates with taxonomic diversity and functional dominance on a global scale. Global Ecology and Biogeography, 23(5), 563-573.
Keenan, T. F., Gray, J., Friedl, M. A., Toomey, M., Bohrer, G., Hollinger, D. Y., ... & Yang, B. (2014). Net carbon uptake has increased through warming-induced changes in temperate forest phenology. Nature Climate Change, 4(7), 598.
Oechel, W. C., Callaghan, T., Gilmanov, T., Holten, J. I., Maxwell, B., Molau, U., & Sveinbjörnsson, B. (Eds.). (2012). Global change and Arctic terrestrial ecosystems (Vol. 124). Springer Science & Business Media.
Seto, K. C., Güneralp, B., & Hutyra, L. R. (2012). Global forecasts of urban expansion to 2030 and direct impacts on biodiversity and carbon pools. Proceedings of the National Academy of Sciences, 109(40), 16083-16088.
Tahir, M., & Amin, N. S. (2013). Photocatalytic reduction of carbon dioxide with water vapors over montmorillonite modified TiO2 nanocomposites. Applied Catalysis B: Environmental, 142, 512-522.
web.viu.ca. (2018). More on Residence Times and Half-lifes. Retrieved from https://web.viu.ca/krogh/chem302/residence%20time.pdf
Welsh, W. F., Orosz, J. A., Carter, J. A., Fabrycky, D. C., Ford, E. B., Lissauer, J. J., ... & Torres, G. (2012). Transiting circumbinary planets Kepler-34 b and Kepler-35 b. Nature, 481(7382), 475.
Wild, M., Folini, D., Schär, C., Loeb, N., Dutton, E. G., & König-Langlo, G. (2013). The global energy balance from a surface perspective. Climate dynamics, 40(11-12), 3107-3134.
Yu, C. H., Huang, C. H., & Tan, C. S. (2012). A review of CO2 capture by absorption and adsorption. Aerosol Air Qual. Res, 12(5), 745-769.
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