Exercise C Paleeclgythe Use Of Pollen To Study Past Vegetation
- If your campus has a palynologist (mosdy likely in the geology department) who is doing work in palcoc-cology, you may be able to obtain slides that represent local sites.
- The site mentioned in the lab exercise is Fcrndalc Bog in southeastern Oklahoma, and you can prepare pollen slides that simulate core samples from this site. These simulated slides are based on die pcrcents from the actual samples. Thcv differ in that there are fewer pollen types in the simulation.
- Place each of the following pollen mixtures into a separate small bottle or vial. You may need to wash the pollen off the weighing paper with a small amount of distilled water (1.0 to 2.0 ml). Add additional distilled water to the vial to bring the total to 10.0 ml and mix well. The following pollen mixtures represent the major vegetation during the time periods from Fern-dale Bog Wore. This is a simplified pollen profile, since other pollen types have been omitted.)
- 700 years ago (20 mg pine. 25 mg oak, 3 mg grass, 3 mg ragweed)
- 2,000 years ago (25 mg pine, 15 mg oak. 3 mg grass, 2 mg ragweed)
- 5,000 years ago 110 mg pine, 25 mg oak, 6 mg grass, 2 mg ragweed)
- 8,000 years ago (5 mg pine. 25 mg oak. 21 mg grass, 3 mg ragweed)
- 12,000 years ago (5 mg oak, 5 mg grass, 50 mg ragweed) ^
- Isabel microscope slides with the time period. Place one drop of the pollen mixture on each slide. Place the slides on a slide warmer until all the water evaporates. Add a drop of melted glycerin jelly mounting medium. Using a toothpick, stir well to distribute the pollen through the mounting medium. Add a coverslip and gently press down. Remove the slides from the slide warmer and allow the mounting medium to solidify. Remove any cxcess mounting medium. Repeat for the other time pcricxls.
- Interpretation: Ragweed is a pioneer plant that quickly invades disturbed areas. Dominance by grasses may indicate a prairie phase in succession and/or limited rainfall. Tree spccics indicate more rainfall and/or later stages in succession. Have the students describe what thcv think mav have been the
changes in vegetation and climate during the past 12.000 years.
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