Earth Lab: Degrees of Change Pollen Grains and Climate Change

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1 Earth Lab: Degrees of Change Pollen Grains and Climate Change Pre Museum Visit Activity Objectives and Overview In this exercise students will replicate the method of pollen fossil analysis used by plant paleontologists to determine climates in the past. They will investigate the characteristics of pollen shown in an illustration of different plant species, and match up unknown pollen samples with known samples. Using the information about the climate associated with known plant species plants species and the dates of the sedimentary layers containing the pollen, they will determine the climate in previous years. Time Frame 1-2 class periods (45 min. each) Background Evidence from the fossil record indicates that the earth s climate has changed many times in the past, but recorded weather records exist for only the last few hundred years. Scientists have, however, learned to identify plants that grew in a particular region over time and been able to infer climates that existed in the long-ago past. The data associated with a variable that cannot be measured directly is known as proxy data. Scientists use of information from ice cores to determine climate from the past is another example of proxy data. Paleobotanists collect cores of lake sediment that contain pollen samples deposited in layers over a period of time. The cores, usually about 10 m by 5 cm, are treated with chemicals so that the pollen grains of chemically resistant organic matter are separated out. The sedimentary layers are dated using carbon dating methods, and the pollen grains are compared to known plant species and identified. Since scientists know the temperature and precipitation preferences for many plants, they can infer the climate for the plant producing the pollen grains in the sedimentary layers. Information about previous climate changes over time help scientist to understand current changes in climate and their impact on species of plants and animals. The data for this activity was taken from Battle Ground Lake in Washington State, and similar data is available for Black Hawk, Colorado. Materials (per group) 1 pair forceps 1 pie pan or paper plate for sediment sample 1 small plastic bag with sediment layer sample 1

2 1 pollen analogue consisting of colored paper dots 1 copy of Table1: Composition of Pollen Samples 1 copy of Table 2: Pollen Key and Climatic Characteristics of the Vegetation for Battle Ground Lake, Washington 1 copy of Table 3: Plant Species by Sediment Layer for Battle Ground Lake, Washington 1 Pollen Illustration (Per class) 1 large graduated cylinder or clear container for sediment column 5 types of sediments i.e., dark soil, sand, potting mixture, fine gravel, vermiculite, peat moss, etc. 11 sheets of colored paper for punched dots (25 per group) Lesson Concepts 1. Pollen is unique for each plant species. It can survive for a long time and can be used for plant identification. 2. Plants thrive under certain conditions of temperature and precipitations. 3. The climate in previous eras can be inferred by identifying plants from fossil pollen and matching to the climatic preferences of those plants. Preparation This activity involves significant teacher preparation, so it is suggested that student lab assistants be enlisted for help. 1. Fill a large cylinder or clear container with five layers of sediment (potting soil, vermiculate, sand, gravel, garden soil, etc.) and mark the layers as shown in the diagram. 2. Assign a letter for each of the 11 sheets of colored paper. For example, A could be dark red; B could be blue, etc. Make a table of dots based on your classification system that students can use as reference during the activity. Or, have students make this table under your direction. Also, assign a number to each sediment layer with the bottom as 1 and the top as Punch out dots from the colored paper so that every student has a sample with 25 pollen analogues. The composition of the pollen components are found in Table 1. 2

3 4. Make up a pollen sample bag for each group of two or three students using ¾ cup of sediment and 25 dots. 5. Make copies of the Tables 1-3 and the Pollen Illustration. Procedure 1. Review with students the purpose of this activity, the contents of their sample bag, and the other equipment they will use. 2. Have students open their sample bags, place the contents in the plate, and start classifying their pollen samples by color. 3. Check that students are recording their data in the Tables. Some students may require help calculating percentages of the whole. Have them reach consensus on the identity of their plant pollen and the climate conditions in which it was deposited. 4. If possible, have students work with another sample bag. 5. Have each student group discuss its findings. 3

4 Table 1: Composition of Pollen Samples Layer 1 Layer Present - 4,500 years before present (ybp) Pollen Dot Number Plant Species Color of Dots western cedar G 6 western hemlock A 5 Douglas fir B 10 alder D 4 Percentage of Pollen Layer 2 4,500 ybp - 9,500 ybp Douglas fir B 3 oak J 3 mixed meadow species I 19 Layer 3 9,500 ybp- 11,200 ybp Douglas fir B 7 grand fir E 5 alder D 13 Layer 4 11,200 ybp - 15,000 ybp lodgepole pine H 7 Engelmann spruce F 3 grand fir E 3 grasses and sedge C 9 alpine sagebrush K 3 Layer 5 15,000 ybp - 20,000 ybp grasses and sedges C 15 alpine sagebrush K 4 lodgepole pine H 4 Engelmann spruce F 2 4

5 Table 2: Pollen Key and Climatic Characteristics of the Vegetation for Battle Ground Lake, Washington Color or Shape Code A B C D E Plant Species Western hemlock Douglas fir Grasses & sedges Alder Grand fir Climatic Characteristics Principal dominant tree of many lowland, temperate sites. Requires very moist, temperate conditions for growth. Broadly distributed throughout the Pacific Northwest from moderately cool to warm sites. Grows best under temperate, somewhat moist conditions. These grasses and sedges are typically found in very cool alpine/subalpine meadow sites characterized by very cool summers, harsh winters, and short growing seasons. Widespread throughout the Pacific Northwest, often colonizing gravel bars or other poor soils, prefers abundant water and can grow in cool climates. Found at mid-elevations in the Cascade mountains. Grows in cool climates, but not as cold tolerant as trees found at higher altitudes. F Engelmann spruce Found in cold, usually sub-alpine sites. G Western cedar Found only in temperate, very moist climates. H I J K Lodgepole pine Mixed meadow species Oak Alpine sagebrush Found in areas of very cool climates typically growing on poor soils, often at high altitudes (above 3,500 feet) under the present climate. This pollen is typical of a mixture of herbaceous plants common to warm temperate meadowlands, such as may be found in the Willamette Valley in Oregon. Typically, these species grow in areas of warm summer temperatures and summer drought. Found in warm - temperate sites characterized by dry, warm summers such as can be found from Oregon's Willamette Valley south into California. Woody, low-growing shrub related to the sagebrush of eastern Washington and Oregon. Found only at high-altitude, cold sites. 5

6 Table 3: Plant Species by Sediment Layer for Battle Ground Lake, Washington Plant Species Sediment Layer Western hemlock Douglas fir Grasses & sedges Alder Grand fir Engelmann spruce Western cedar Lodgepole pine Mixed meadow species Oak Alpine sagebrush 6

7 Pollen Illustration Illustration of three pollen types from Washington State. For additional photos of pollen consult internet resources such as Google Images. Reflections and Conclusion 1. Describe the different shapes and colors of the pollen in the picture. 2. Match the dots with the letters and write down the plant species for your sediment layer. 3. Fill in the rest of your data table using the data provided by your classmates. 4. Describe the climate conditions during the deposition of pollen in your sediment layer using Table 2. 7

8 Exercises for Post-Museum visit Exercise 1: Planning an Energy-Saving Project When you and your students visited the Earth Lab exhibit at the Koshland Science Museum, you were asked to think of an individual, family or classroom project to save energy. Decide with your class what kind of action plan you and they want to develop. Have the students determine the goals, implementation, and assessment of their project(s) and write it up in their notebooks. They may want to do some research by visiting the EPA, Department of Energy education, NOAA or similar websites. At the end of the project they can report their results to the class if they had an individual project or to other classes if they had a class project. Exercise 2: Pollen Analysis of Lake (place school or class name here) Construct a hypothetical lake containing two of the sediment layers selected from the key the students have already used to determine climate. Show the raw data from the layers and ask the students to determine in writing, the climatic history of the area. References This activity has been modified by Kitty Lou Smith from one developed by the University Center for Atmospheric Research and can be found on its website: 8