HR: 16:05h
AN: GC54A-01    [Abstracts]
TI: Effects of Past Climate Changes on Ecosystem Biogeochemical Cycles in Rocky Mountain Forests and Lakes
AU: * Shuman, B
EM: bshuman@uwyo.edu
AF: University of Wyoming, Dept of Geology and Geophysics, Laramie, WY 82071,
AU: Mechenich, M F
EM: mmecheni@uiuc.edu
AF: University of Minnesota, Limnological Research Center, Minneapolis, MN 55455,
AU: Stefanova, I
EM: stefa014@umn.edu
AF: University of Minnesota, Limnological Research Center, Minneapolis, MN 55455,
AU: Henderson, A
EM: ahenderson@gmail.com
AF: University of Minnesota, Limnological Research Center, Minneapolis, MN 55455,
AU: Donnelly, J P
EM: jdonnelly@whoi.edo
AF: Woods Hole Oceanographic Institution, Geology and Geophysics, Woods Hole, MA 02543,
AB: Ongoing climate trends will likely alter how forest ecosystems produce important goods and services, in part, by changing ecosystem responses to disturbances, such as fires and land-use. Disturbances induce forest succession and thus dramatically change the flow of water and nutrients through a given ecosystem. However, long-term ecosystem responses to disturbance, especially regarding nutrient pools and cycling rates, are poorly documented, and less is known about the effects of century-scale climate trends on these responses especially with respect to moisture. Here, we show biogeochemical responses to repeated (>20) episodes of disturbance and succession in a single ecosystem under a range of climatic conditions over 2000 years. Our lake sediment record shows regular fluctuations in the flux of base cations and other macronutrients from lodgepole pine ( Pinus contorta) forests in northern Colorado following catastrophic stand-replacing fires. Post-fire elemental fluctuations are consistent with ecosystem theory regarding the re-equilibration of biomass and nutrient pools during succession, but show systematic variation that has been previously undocumented. The time span of post-fire re-equilibration correlates positively with measures of fire severity, which is consistent with hypotheses that seed dispersal and soil recovery likely slow re-growth after large or severe fires. Likewise, dry conditions during the Medieval Climatic Anomaly (MCA, 1200-500 yrs BP) altered elemental fluctuations and, thus, generated post-fire pulses of lake eutrophication that were not evident during other periods. The interaction of climate and disturbance, therefore, has important consequences for ecosystem function and services, including the quality of aquatic environments.
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0458 Limnology (1845, 4239, 4942)
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 1812 Drought
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting