HR: 15:10h
AN: B43E-07 INVITED     [Abstracts]
TI: Fire Cycles on the Northern Great Plains and Their Relation to Prairie Drought
AU: * Brown, K J
EM: kendrik@duke.edu
AF: Duke University, Biology Department Box 90338, Durham, NC 27708 United States
AU: Clark, J S
EM: jimclark@duke.edu
AF: Duke University, Biology Department Box 90338, Durham, NC 27708 United States
AU: Grimm, E C
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 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: Drought is a naturally occurring, recurrent phenomenon that has historically gripped large regions of the United States, often with catastrophic consequences. Human insight into the duration, frequency, and dynamics of drought is largely limited to short-term observation. For example, the "Dust Bowl" of the 1930's in the central plains is one of the most vivid cases of prolonged drought in the USA and yet it persisted for less than a decade. To circumnavigate this limited perspective, we employed a paleoenvironmental approach to better characterize landscape response to prairie droughts and specifically document fire response to droughts. Two long sediment cores were collected from Kettle and Brush lakes in the Northern Great Plains (NGP) and age-depth models were developed for the cores by fitting locally weighted loess curves to AMS radiocarbon dates. The cores were continuously sub-sampled at high resolution (1 cm) for particulate charcoal, pollen, sediment mineralogy, and loss-on-ignition. In contrast to recent human observation, spectral and wavelet analyses reveal that multi-decadal to centennial drought cycles have persisted on the northern plains for much of the last ca. 10,000 years, though there were intervals where the cycles were muted, further compounding the dynamics of climate on the plains. In the latest Holocene interval, 160-year fire and drought cycles are clearly denoted. Fires are more common during the wet phases of the drought cycles because moist conditions foster increased grass productivity, resulting in greater fuel loads. In contrast, forbs expanded during the drier periods, limiting fuel loads which resulted in less fire. The charcoal data reveal three general Holocene fire intervals on the NGP associated with millennial-scale changes in climate. In general, the incidence of fire was greater in the early- and late-Holocene with less fire during the warm dry mid-Holocene.
DE: 1812 Drought
DE: 1845 Limnology
DE: 1620 Climate dynamics (3309)
DE: 1655 Water cycles (1836)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting