Page 1 Name ______

Module 1B: Photosynthesis and Ecosystems

Part 1: Ecosystems and photosynthesis There are three main types of photosynthesis found on this planet: CAM, C4 and C3 . C3 photosynthesis is the dominant form and is found in plants ranging from algae to Redwoods. Even though C4 plants comprise only 3% of living flowering plants most of which reside in the grass family (or Poaceae), these plants still produce over 20% of global primary productivity. They dominate tropical and warm-temperate grasslands, and include vital food crops, invasive weeds, and even potential sources of biofuels (i.e., corn). An even smaller percentage of plants use CAM but their numbers parallel their distribution. Today they can only be found in extremely arid environments. As hinted by the distribution of CAM plants, photosynthesis is strongly constrained by water availability and temperature. These two environmental factors are the primary controls on the distribution and abundance of photosynthesis types amongst ecosystems. For example, C3 photosynthesis is much more efficient at lower temperatures than C4 photosynthesis. These differences in photosynthetic and water use efficient can effect nutrient and water cycling within ecosystems. Thus, the dominant mode of photosynthesis has strong effects of ecosystem functioning (e.g., fire).

1a. Below is a map showing the simulated distribution of C4 grasses on the globe. (Adapted from Woodward et al. 2004) Using the same cities as for Module 1A, fill in the predicted amount of C4 grasses in these regions and explain briefly why C4 is found in that abundance in the region. Page 2 Name ______

Annual Annual Predicted C4 abundance City Temp. Precip. (high/moderate/low) (°C) (cm) Briefly explain the abundance. Chicago, IL 9 89

Tuscon, AZ 21 22 Tabora, 23 87 Tanzania Toolik Lake, -8 18 AK Beijing, 12 63 China Valdivia, 13 240 Chile Tromso, 2 101 Norway Chanthaburi, 27 282 Thailand Cairo, Egypt 30 29

1b. What patterns do you see in the distribution of C4 grasses? Where are they mostly found? (Northern/Southern Hemisphere; High/Low Latitudes etc.). How do these patterns relate to the maps of precipitation and temperature in module 1A? Page 3 Name ______

Below is a flow diagram showing the dynamic relationship between C4 -grass cover, fire, CO2 and the environment. (Blue: environment; Green: vegetation; Red: driver; Orange: effect). Pluses correspond to a “positive effect” and minuses to a “negative effect”. For example tree growth has a negative effect on tree mortality. (Modified from Beerling and Osbourne 2006.)

1c. Locate a “positive feedback loop” in the above diagram (a loop with an even number of positives and minuses). What do you think would happen to an ecosystem if this loop continued unchecked? Page 4 Name ______

1d. In your own words, explain how fire affects the amount of C4 grass cover.

1e. In your own words, explain how CO2 affects the amount of C4 grass cover. (Bonus: How does CO2 affect the amount of fire?)

1f. Below is a diagram showing the interactions between fire and herbivores (grazers eat grass; browsers eat trees and shrubs). How does adding herbivory modify the effect of fire on C4 grass cover? Page 5 Name ______

Part 2: The plant and photosynthesis The type of photosynthesis a plant uses is often reflected in its physiognomy or “characteristic physical structure.” Below are pictures of typical plants that use each of the three types of photosynthesis. Brainstorm what characteristics that make them different from each other and how these structures relate to water use efficiency (e.g. size, leaf shape, overall structure etc.) in the space next to each picture.

2a. Saguarro cactus (CAM)

2b. Red Maple (C3)

2c. Switchgrass (C4)

2d. Bonus: Can you think of any trees with C4 characteristics? ______Page 6 Name ______

Part 3: Plant tissues and photosynthesis On the scale of tissues and cells, plants show marked differences in their primary structure. Each type of photosynthesis has its own modified physical architecture and mode of exchanging gases and producing sugars from CO2. Below is a simplified diagram showing these differences. Pay special attention to where and when photosynthesis (Ps) is occurring and where and when a plant exchanges water and CO2 with the environment. Page 7 Name ______

3a. What are the major differences between how C3 , C4 and CAM plants acquire CO2 and convert then it to sugars?

3b. What are the trade-offs for C4 plant that prevent them from being successful in regions where C3 plants dominate? (Think in terms of trade-offs. Do C4 plants sacrifice anything to be “well adapted” under certain climate conditions. No organism can be good at everything. There are always trade-offs.)

3c. What type of photosynthesis do you believe first appeared in the fossil record? Justify your answer by referring to the above figures. Page 8 Name ______

Part 4: Photosynthesis and data visualization (Take home) Ecologists and paleoecologists, like most scientists, need a way to convert all those crazy numbers (Data) into a form that can be easily understood and shared. This can be easily done by creating figures and diagrams much like the flow diagrams or map in Part A. Below we’ve provided a table of simulated data derived from a grassland lake record representing the past 10,000 years (also provided in a spreadsheet). Doesn’t that look scary?! It needs to be repackaged if any sane scientist (or student) wants to produce hypotheses.

Percent Percent Charcoal CO Charcoal CO time C 2 time C 2 pieces 4 (ppmv) pieces 4 (ppmv) Pollen Pollen 0 444 63 310 5250 218 21 252 250 509 55 300 5500 955 97 249 500 483 59 295 5750 816 96 247 750 503 66 283 6000 921 99 244 1000 459 73 279 6250 930 96 242 1250 612 67 278 6500 860 96 220 1500 603 71 278 6750 966 98 236 1750 462 64 277 7000 279 80 234 2000 480 74 290 7250 304 43 231 2250 761 96 265 7500 369 38 229 2500 772 90 274 7750 297 54 226 2750 780 84 272 8000 413 53 230 3000 785 87 280 8250 440 53 221 3250 802 90 269 8500 405 42 219 3500 803 83 267 8750 330 27 220 3750 154 22 265 9000 336 54 200 4000 176 3 263 9250 631 25 212 4250 41 10 261 9500 312 48 210 4500 206 10 259 9750 674 80 208 4750 92 6 290 10000 302 25 206 5000 6 24 257

4a. How do you think you should graph the above data? (e.g., histogram, scatterplot, pie chart etc.) Page 9 Name ______

4b. Thanks to the advent of the Internet there are no limits to what you can find. This includes a wonderful website (http://www.incompetech.com/graphpaper/) that allows you to create your own graph paper! Using a graph paper of your own devising and artistic talent, create a graph using the table above which you think would best represent the data. Basic rules to follow: 1) the figure should be easy to understand at a glace; 2) everything should be labeled; 3) it should be visually striking; 4) be creative! (Do not worry about getting every data point. Be concerned only with the general trends.) For inspiration check out Information is Beautiful (www.informationisbeautiful.net): a blog devoted to visualizing data!

4c. Using your favorite spreadsheet program (or preferably Tableau), construct the figure using the provided spreadsheet file. How does it compare to your own figure?

4d. Construct a hypotheses on what is “controlling” the amount of C4 grass on the landscape. Is it CO2? Fire? Something else all together? What led to you concluding on this particular hypothesis? Given what you know from Part A. Could other environmental factors not shown here because the patters in C4 you see?