HR: 0800h
AN: PP31A-1510    [Abstracts]
TI: Vegetation Dynamics in the Kenai Lowlands, Alaska during the Late Pleistocene and Holocene
AU: * Jones, M C
EM: mjones@ldeo.columbia.edu
AF: Dept. of Earth and Environmental Sciences, Columbia University, 557 Schermerhorn Extension Columbia University, New York, NY 10027
AU: Peteet, D M
EM: peteet@ldeo.columbia.edu
AF: Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025
AU: Peteet, D M
EM: peteet@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964
AB: The use of paleoinformation through ecosystem reconstruction can help us understand the behavior and sensitivity of the boreal forest as climate continues to change. A 2.5-meter sediment core extracted from Swanson Fen, a muskeg in the northern Kenai Lowlands on the Kenai Peninsula, Alaska, provides a sensitive Holocene paleoenvironmental record that lies in an ecotone between interior boreal forest and maritime coastal forest today. The core was sampled at 2-cm intervals and processed for pollen and spores. Five intervals were dated using AMS radiocarbon dating, and the basal macrofossils produced an age of 12,245 ±45 radiocarbon years. The central Kenai Peninsula Lowlands underwent a number of marked vegetational and climatic changes since deglaciation. Four distinct vegetation zones reveal changes starting in the late Pleistocene. The pioneer vegetation includes a dominance of herbaceous ( Artemisia, Apiaceae, Asteroideae)and shrubby ( Betula) species. The second zone (beginning at 9890±45 radiocarbon years) and marking the Holocene boundary, shows a striking increase in Polypodiaceae (ferns) and Picea (spruce) and a decrease in shrubby species such as Betula, indicative of warming. The third zone indicates a decline in Polypodiaceae and a reemergence of Betula species, while the final most recent zone reveals a rapid resurgence in Picea and Tsuga mertensiana (Mountain hemlock) species. While a general warming trend occurred following deglaciation, vegetation patterns suggest extended periods of increased precipitation, for example in the early Holocene, as is evidenced by the plethora of Polypodiaceae. A movement and an intensification of the Aleutian Low could explain these periods of increased precipitation over the Kenai Peninsula. Alternatively, this spike in Polypodiaceae can be explained by increased disturbance. The presence of 10 % Picea pollen at the base of the core suggests that one of the Picea species may have survived the last glaciation in the region. A decrease in Picea pollen and an increase in herbaceous ( Artemisia, Apiaceae, Asteroideae) pollen in the late Quaternary suggest a reversal to cooler conditions before warming resumed at the Holocene boundary, and Picea once again increased. This coincides with the timing of the Younger Dryas in the North Atlantic, and suggests that this phenomenon was felt on the Kenai Peninsula.
DE: 0429 Climate dynamics (1620)
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 0476 Plant ecology (1851)
DE: 3344 Paleoclimatology (0473, 4900)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005