carbon cycle
; climate change
; flushing
; Glacial Lake Agassiz
; greenhouse gas
; hydrogeology
; methane
; methanogenesis
; peatland
; porewater
; precipitation (climatology)
; recharge
; rhizosphere
; solute transport
; time series
; water chemistry
; Minnesota
; United States
英文摘要:
Northern peatlands are an important source for greenhouse gases, but their capacity to produce methane remains uncertain under changing climatic conditions. We therefore analyzed a 43 year time series of the pore-water chemistry to determine if long-term shifts in precipitation altered the vertical transport of solutes within a large peat basin in northern Minnesota. These data suggest that rates of methane production can be finely tuned to multidecadal shifts in precipitation that drive the vertical penetration of labile carbon substrates within the Glacial Lake Agassiz Peatlands. Tritium and cation profiles demonstrate that only the upper meter of these peat deposits was flushed by downwardly moving recharge from 1965 to 1983 during a Transitional Dry-to-Moist Period. However, a shift to a moister climate after 1984 drove surface waters much deeper, largely flushing the pore waters of all bogs and fens to depths of 2 m. Labile carbon compounds were transported downward from the rhizosphere to the basal peat at this time producing a substantial enrichment of methane in Δ14C with respect to the solid-phase peat from 1991 to 2008. These data indicate that labile carbon substrates can fuel deep production zones of methanogenesis that more than doubled in thickness across this large peat basin after 1984. Moreover, the entire peat profile apparently has the capacity to produce methane from labile carbon substrates depending on climate-driven modes of solute transport. Future changes in precipitation may therefore play a central role in determining the source strength of peatlands in the global methane cycle. �2016. American Geophysical Union. All Rights Reserved.
Department of Earth Sciences, University of Minnesota, Twin Cities, Minneapolis, MN, United States; Department of Earth Sciences, Syracuse University, Syracuse, NY, United States; Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL, United States; School of Earth and Climate Sciences, University of Maine, Orono, ME, United States; U.S. Geological Survey, Lakewood, CO, United States; NASA Goddard Institute for Space Studies New York, New York, NY, United States; ARCADIS US Inc., Pittsburgh, PA, United States
Recommended Citation:
Glaser P,H,, Siegel D,et al. Climatic drivers for multidecadal shifts in solute transport and methane production zones within a large peat basin[J]. Global Biogeochemical Cycles,2016-01-01,30(11)