ENVS 202 Name: Ricki Marshall Winter 2019 Homework Assignment #1: 25 pts Please circle or bold your discussion section: 9AM 10AM 11AM Noon 1PM 2PM 3PM 4PM Laura Laura Jamila Jamila Geoffrey Geoffrey Chantel Chantel 1. These questions deal with the case study on Northeastern forests in Chris Bright’s article, The Nemesis Effect. (4 pts total) A. What atmospheric gas is produced by the interaction of sunlight and nitric oxide (NO)? (1) The atmospheric gas is called ozone (O3). B. Are forests more or less dense in this region than 200 years ago? (1) Forests are more dence now because these are second growth forests. Also, there wasn’t as much agriculture as in the past. C. Explain the effects of acid rain on the forests in this region (2) Acid rain is a byproduct of additional nitric acid from airborne nitrogen and sulfuric acid, which is primarily from coal-burning power plants. The acid deposits rob the soil of essential plant nutrients such as calcium and magnesium, which causes aluminum to be released in the soil, which makes it hard for trees to take up water. In other words, the acid rain lowers the pH of the water, which can be lethal to trees; in addition, the acid rain has started leaching out nutrients in the soils, which slows growth of trees. Trees' leaves and needles are also harmed by acids, making trees unable to become dormant when it’s cold. When enough of the needles die, the tree dies. The acid rain hasn’t just made the soils less nutritious- it has also made them toxic. This weakening of the forests’ immune system is likely to upset the balance between the trees and their pathogens. (pg. 15-17) 2. (exam) These questions come from the reading by Cudmore and the exercise done in lecture (5 pts total) A. Individuals of what tree species are less abundant in the hills surrounding the Willamette Valley today? (1) The Oregon white oak (or Garry oak, or just oak). B. Individuals of what tree species are more abundant in the hills surrounding the Willamette Valley today? (1) The Douglas-fir. C. True or False: Fire management techniques practiced by the Kalapuya destroyed all Garry Oaks (1) False. D. Are there more or fewer sloughs, oxbows, and side channels in the Willamette River today compared with that of 150 years ago? (1) Fewer.E. What major human influence accounts for the differences you have described? (1) Humans caused fire and converted natural prairies, shrubland, and savanna into agriculural and developed land. The wetlands were tiled, drained or filled for the production of hay, grain, and cattle grazing and later for roads, houses, and industry. 3. (exam) Consider the following simple community (6 pts total) Caddis fly larvae feed on algae on rocks in streams. Juvenile salmon feed on caddis fly larvae. A. Put signs on each of the arrows below to indicate these relationships. (one sign per arrow) (1) B. On the graph show the effect of caddis fly larvae on algae as indicated by this scenario. Be sure to use the proper axes and use labels: algae, caddis fly larvae, low, high (2) C. Add an arrow and a sign to the diagram in part A to indicate the effect that salmon have on algae in the stream when their bodies decay and relase nutrients such as nitrogen and phosphorus. (1) D. What kind of feedback loop exists when looking at algae, caddis fly, and salmon? Briefly explain in words how it works. (2) Self enhancing or positive feedback. If algal populations increase, there would be more caddis flies, which support more salmon, which add more nutrients back to the stream to support even more algae. 4. (exam) Use this causal map to answer the questions below (10 pts total)In recent weeks, increased number of California sea lions have been seen off the Oregon coast. Using this over-simplified account of interactions between some of the species that are affected… Sea lions eat salmon. Salmon eat herring and anchovy. Herring and anchovy eat copepods. A. Put the proper sign ( + or - ) on each arrow in the diagram. (each sign must be associated with one arrow) (3) B. What is a negative feedback loop? (1) A self-dampening loop or one in which an initial perturbation in one direction ends up being lessened, cancelled, or reversed when the loop is completed. C. Identify one negative feedback loop on the diagram and explain in words how it operates (2) An increase in sea lions means more samlon are eaten which support fewer sea lions thus reduction the sea lion population or conversely. A decrease in sea lions means fewer salmon are eaten. D. What is a positive feedback loop? (1) A self-enhancing loop or one in which an initial perturbation in one direction ends up causing a further change in the same direction in that variable when the loop is completed. It has nothing to do with whether the relationship is beneficial. E. Identify one positive feedback loop on the diagarm and explain in words how it operates (2) More salmon means fewer herring which means more copepods which means more anchovy which means more salmon. F. Add to the causal map a box, an arrow, and a plus or minus sign to indicate the following information (1) El Niño events (which tend to cause warmer seas) reduce the number of