HR: 17:35h
AN: GC52B-07    [PDF]
TI: The History of Fire on the Northern Plains, USA, and its Response to Holocene Drought-Cycles
AU: * Brown, K
EM: kendrik@duke.edu
AF: Duke University, Department of Biology Box 90338, Durham, NC 27708 United States
AU: Clark, J
EM: jimclark@duke.edu
AF: Duke University, Department of Biology Box 90338, Durham, NC 27708 United States
AU: Grimm, E
EM: grimm@museum.state.il.us
AF: Illinois State Museum, Research and Collections Center 1011 East Ash Street, Springfield, IL 62703 United States
AU: Donovan, J
EM: donovan@geo.wvu.edu
AF: West Virginia University, Department of Geology and Geography 425 White Hall P.O. Box 6300, Morgantown, WV 26506 United States
AU: Mueller, P
EM: mueller@museum.state.il.us
AF: Illinois State Museum, Research and Collections Center 1011 East Ash Street, Springfield, IL 62703 United States
AB: Extensive drought has periodically gripped large regions of the United States in the past. The "Dust Bowl" of the 1930's in the central plains is perhaps one of the most vivid examples of prolonged drought, climatic extremes, dust storms, crop failure and general human hardship. The impact of future drought conditions potentiated by greenhouse gas emissions may indeed exceed the devastation wrought during historical droughts and thus mandates examination of past drought variability. Two long cores from Kettle Lake (North Dakota) and Brush Lake (Montana) were collected to study past drought variability in the northern plains. An age-depth model was developed for the cores by fitting a locally weighted loess curve to AMS radiocarbon dates obtained from the cores. The cores were continuously sub-sampled at high resolution (1 cm) for pollen, charcoal, and sediment mineralogy. Pollen was extracted using standard techniques and charcoal was sieved from the sediment at 180 um resolution and its area determined through optical microscopy. Minerology was determined using x-ray diffraction. The data reveal that the mid-Holocene was exceptionally warm and dry and that several fire regimes existed throughout the Holocene. In general more fire characterized the early- and late-Holocene with less fire during the mid-Holocene. Spectral analysis of the multi-proxies reveals that 100- to 130-year drought cycles persisted during the early-Holocene in the northern plains. Drought cycles are also observed during the late-Holocene interval. The dry phases of the cycles are characterized by a decline in grasses and fire and an increase in forb vegetation and erosion. The forb response during the mid-Holocene is one of fluctuating Ambrosia pollen whereas Artemisia pollen cycles in the late-Holocene. This change in pollen response may reflect a change in the seasonality of drought from winter to summer over that time. Fires are more common during the wet phases of the drought cycles because more moist conditions permit grassland expansion, resulting in greater fuel continuity.
DE: 0400 Biogeosciences
DE: 1600 GLOBAL CHANGE (New category)
DE: 1699 General or miscellaneous
SC: Global Climate Change [GC]
MN: 2003 Fall Meeting