Your Name:EEMB/ES 171-Winter 2015 Quiz # 1 Read each question carefullyUse the back if you need toTrue or False: If false, briefly explain why. 1. (6) T/F: Cation exchange capacity is an important characteristic of both clays and organic matter.TRUE2. (6) T/F: Soil texture and structure are effectively the same thing.False. Texture is defined by the proportion of sand, silt, and clay particles in the soil. Structure ishow those particles are assembled together into larger structures. 3. (6) T/F: The main resource limiting the productivity of tropical rainforests is typically nitrogen, because the soils are so old and weathered. False: Phosphorus is likely to be a more limiting resource in old weathered soils.4. (6) T/F: Shrubs are declining in the Arctic as a result of global warming.. False. Shrubs are expanding.Your Name:5. (12) If you were considering buying a piece of property to farm, the first piece of information you should probably check is the soils map. Why? Give at least three specifics.A soils map will tell you the name and characterization of the soil in any particular place. That will tell you about:Texture (hence likely water holding capacity and drainage)Depth and the nature of the horizon structureAge and so the degree of weathering in the soil. The likely nature of the native vegetation: forest vs. grassland soil.Overall fertility levels. 6. (10). What is the difference between photosynthesis and net primary production? Photosynthesis is the capture of energy from sunlight and the fixation of CO2 into sugars that canthen be converted into other organic molecules and plant tissues or used to fuel metabolism in other parts of the plant. Net Primary production is the net gain in C by plants. It is equal to Gross Primary Production (photosynthesis – respiration by leaf tissues) minus respiration by other parts of the plant (stems,roots, etc.). 7. (18). You are doing a water balance on an area. The following values are for the summer only. PET = 1500 mmRainfall = 700 mmSoil water = 150 mm this amount of water is in the soil at the beginning of the summera) (6) What is AET for this summer? AET will equal either PET or the amount of water available for plants to use, whichever is LESS.Remember PET is the bill, AET is how much of it you pay. If you can pay it all, do so. If you can’tpay it all, pay as much as you can. b) (6) If all this rain comes in two big thunderstorms, would AET change? Why or why not?During a big storm, PET is low (dark, cold, and wet), while precipitation is large. So during thatshort time, there is more water than can either be evaporated or stored in the soil—the surface soil becomes saturated and the extra water can’t infiltrate quickly. So some water will run off. Hence, less water will be available later and AET will be reduced. c) (6) If the plants in this area had roots that went deep enough to reach groundwater, do you think AET would change? If so, how?YES. If plants can access deep groundwater the amount of water available will be greater and soAET will increase (at least if precipitation is below PET, as it is in this case).Your Name:8. (16) Consider the ecosystem at right. You’ve established thefollowing measurements:1. A flux tower to measure the net ecosystem exchange of CO2 between the ecosystem and the atmosphere.2. Soil flux chambers to measure total soil respiration,which includes root respiration3. A flume on the stream to measure export.Assume there are no other important C fluxes.A. (8) What is the value for Net Primary Production?Net ecosystem exchange (NEE) = NPP – Soil Respiration. In this case, net flux in = NEE, not NPP, since it measured the exchange between the atmosphere and the ecosystem. So NEE (10) = X – 4 Hence, NPP = 14B. (8) What is the value for Net Ecosystem Productivity?Net ecosystem productivity is the overall gain in C after accounting for all sources in andout. NEP = NEE – Other losses (e.g. stream export)So: NEP = 10 -1 = 99. (12) You set up a suite of fertilizer trials to test the fertility of a farm soil. You set up three plots in which you add either N, P, or a combination of both. Treatment Growth (kg)Control 9+N 9+P 14+N +P 18A. From these data, would you conclude that Liebig’s Law applies in this situation? Liebig’s law says that only one resource can limit growth at a time. Hence if adding one nutrient increases growth, adding any other nutrients singularly should not influence growth. However, once you’ve added the limiting nutrient, another likely becomes the new limiting nutrient. So if P increases growth, adding N alone should not increase growth, but adding both N+ P together may increase growth more than adding P alone. Here, the data perfectly fit Liebig’s law—as a sole limiting nutrient, it’s clearly P. However, after alleviating P limitation, the plants become N limited and benefit from the N+P treatment. F l u x t o w e rN e t f l u x i n = 1 0 g C m y- 2 - 1S o i l r e s p i r a t i o n = 4 g C m y- 2 - 1S t r e a m e x p o r t = 1 g C m y- 2 - 1Your Name:10. (18) You are evaluating the likely response of an ecosystem to climate warming. To do this, you measure how much the rate of each process increases as temperature increases. You measure the Q10 value which describes how much a reaction speeds up with each 10° C increase in temperature (a value of 2 means the rates doubles with a 10º C increase; so rate is 1 at10°, 2 at 20°, 4 at 30°, etc.).Process Q10Photosynthesis 2.0Plant respiration 3.0Soil respiration 1.5A. (8) As the temperature increases, will NPP increase or decrease? Why?Respiration increases faster with temperature than does photosynthesis. Therefore NPP should go down as temperature increases. B. (8) As temperature increases, will this system gain or lose carbon? Why?Oops. This is a little tricky. But, the system will almost certainly lose C. Consider:Rate at T1 Rate at T1+10 Rate at T1+20 Photosynthesis 2 4 8Plant Resp. 1* 3 9NPP = GPP – Plant Resp.1 1 -1Soil Respiration 1 1.5 2.25Δ ecosystem C0 -0.5 -3.25I'm assigning Plant respiration a starting value of 1 and Photo of 2 because NPP usually equals about ½ of GPP. I’m assigning soil respiration a value of 1 because at steady state, NPP and Soil respiration should be about equal. OK, so from these simple numbers you can see—plant respiration goes up faster with temperature than does photosynthesis. Thus,