Student Page 1

Plant and Climate Information

Geologists determine the geologic past by studying layers of sediment (material deposited by water, wind, or glaciers) and types of bedrock. Plants, other than those preserved in the fossil record, decompose and become part of the soil. However, one part of the plant, pollen, does not readily decompose.. It has a rugged design. By using a plant's current level of pollen production as a guide, scientists (palynologists) can estimate the approximate biomass of that plant in a given area from the proportion of fossil pollen found in core samples. In Illinois, pollen records from core samples can be used to determine the vegetational history of the state and ultimately the climate in which these plants were growing since the last glaciation.

Years B.P. Species Climate
14,000 - 10,900 Spruce Cooler; glaciers retreating
10,900 - 9,000 Ash Warming
9,000 - 8,500 Deciduous mix Generally warming; wet
8,500 - 8,000 Oak-Hickory; Prairie Warmer; dry
8,000 - 6,000 Prairie Hypsithermal interval (warmer period); the prairie stabilized throughout Illinois
6,000 - 900 Prairie Prairie dominates
900 - 200 Pine/Larch; Prairie Climate cools (Little Ice Age); forest expands
200 - 150 Prairie; Oak-Hickory European settlement; decreasing prairie
150 - present   Arrival of railraods; prairie disappears followed by forest depletion and the appearance of agricultural pollens
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