Horizon III: 12,000-10,000 Years Ago An Open Pond A rise in water level and an increase in temperature approximately 12,500 years ago transformed Cedar Swamp basin from a shallow muddy lake to a deeper pond.  As the climate became milder, spruce, larch, fir and white pine trees as well as deciduous trees spread over the upland.  These trees anchored the soil in the watershed, or land above the pond, slowing the sediment erosion and allowing many new plants to take root at the pond’s edge. 1. Pondweed, Water Lily, Naiad In the core, seeds of water lily and naiad, freshwater plants, as well as macrofossils of pondweed indicate open water conditions and warmer temperatures. 2. Alder Shrubs such as alder at the pond’s edge helped to stabilize the shoreline. 3. Sedges and Rushes Sedges and rushes sunk their roots into the pond’s newly stabilized shoreline. 4. Plants Encroaching on Pond Over time, debris from the plants such as water willow growing on the shore began to fill in the pond’s edges, reducing the amount of open water in the basin. 5. Leatherleaf Leatherleaf and other heaths such as blueberries probably formed a floating mat on the surface of the water. 6. Ducks and geese