Your Name:EEMB/ES 171: Fall 2018 Quiz # 2 Read each question carefullyUse the back if you need toFor T/F questions, if False, explain briefly why.1. (8). T/F: Plants growing in a low nutrient environment generally have higher C/N ratios thanthose in higher nutrient environments.True. They make tissues that are N-poor and so are C rich. Hence a high C/N ratio2.(8). T/F: All plants wilt and die when the water potential drops to –1.5 MPa. False. This is the conventional value for crop plants. Plants adapted to drier environments can often tolerate lower values. 3. (8). T/F: Plants take up their carbon from soil organic matter. Nope. From CO2.Your Name:4. (16) Consider a bacterium in the soil asshown here. Assume that water is neither flowing into or out of the bacteriumThe bacterium has a low (s because it has accumulated amino acids. The bacterium can handle a maximum (p of +0.4 MPa—if it goes above that, the cell will rupture. A. (8) What must the (s of the soil solution be (assuming that there are no other components of (w to worry about?Since water isn’t flowing, then (w is the same inside and out. So:(p + (s for bacterium = (m + (s for soil+0.1 -0.7 = -0.6 for bacterium So (s for the soil must equal -0.2 MPa.B. (8) If you now water the soil to abruptly raise the (m of the soil to –0.01 MPa, what will happen to the supply of small labile organic molecules and nitrogen that is free in the soil? Why?Now the (w of the soil will be higher than that of the bacteria. To equilibrate with a water potential +-.4 MPa greater than it was a second ago, the (p inside would have to rise to +0.5 MPa. It can’t do that and will rupture, spilling its guts into the soil: lots of small N and P rich organic molecules.Your Name:5. (18) You do a study on the decomposition of three different plant species. You collect litter from each and place them separately in litter bags. You place them in the field in two different forest ecosystems and measure their decomposition rate. Decomposition constantk in different sitesPlant species Lignin N Site A Site BA 30% 1.0% -0.1 -0.05B 25% 2.5% -0.3 -0.15C 20% 1.0% -0.2 -0.1A. (8) Why does species B decompose faster than species C? Lignin/N ratios for the litter species:A: 30B: 10C: 20 Species B has the lowest lignin:N ratio and so is likely to decompose the fastest. Please note that merely saying it decomposes slower because it has a lower k value is NOT an answer. The k value describes the decomposition rate—it doesn’t explain it. That’s like saying a car goes slowly because the speedometer records a low speed. You need to explain why the k value is low. B. (10) Come up with TWO hypotheses to explain the decomposition dynamics in Site B relative to Site A. Decomposition in Site B is consistently slower than it is in site A. Why might that be? Site B might be:ColderDrierSaturated with water (e.g. too wet)Your Name:Nutrient poor6. (14) You are studying a plant that forms thin, nitrogen-rich leaves and has a high photosynthetic rate. It is native to an area where there are many herbivorous insects (e.g. caterpillars, leaf-miners, and beetles). Yet, this plant does not get eaten by these insects. Are you surprised? Why or why not? What might explain this pattern? This plant clearly produces leaves that are, by many traits, high quality forage for herbivores. But they don’t get eaten. So they must be chemically defended: alkaloids, tannins, or other chemicals that the plant has evolved to protect against these native herbivores. 7. (14) Why do N-fixing plants often dominate in early primary successional environments such as recently deglaciated sites in Alaska and the volcanic ash fields on Mt. St. Helens? Because in these recently exposed areas, the soils are young and N-poor. So until enough N accumulates in the soil, there can’t be very much plant growth. N-fixers are therefore frequently early colonizers—there is lots of light and so, energy, and there are likely plenty of mineral nutrients. The only major thing missing is N. 8. (14) A farmer explains to you that they are very concerned about their role in global climate change, and so to help manage fertilizer use, he monitors trace gas emissions from his crop fieldsand says that he never measures any N2O coming off his fields, so he’s confident that he is not contributing to either global warming or ozone depletion through N2O emissions. How do you respond?The farmer is focusing solely on what is happening on his field—but ignoring the fate of any nitrate that may run off those fields into waterways and wetlands. So if he is still using too much N fertilizer (i.e. more than the plants can take up), any excess is likely to run off and may well be denitrified to N2O downstream. You need to consider the overall fate of all the applied fertilizer—not just what is happening immediately