HR: 0800h
AN: B31A-0063    [Abstracts]
TI: Enriched groundwater seeps in Vermont's forest ecosystems: sources or sinks for nitrate?
AU: * Kaur, A J
EM: akaur@uvm.edu
AF: University of Vermont, 105 Carrigan Drive, Burlington, VT 05405, United States
AU: Ross, D S
EM: dross@uvm.edu
AB: It is well known that wetter areas in the landscape can be hotspots for denitrification but it is not well appreciated that enriched seeps could also be hotspots for nitrification. Such seeps are high in calcium and pH relative to surrounding soils, reflecting less weathered bedrock or till. The various N fluxes may differ markedly between poorly drained soils in or near the seep and well drained soils away from the seep. We are investigating this in a study in two watersheds in Vermont comparing in-seep soils with nearby well drained soils. The sites are the two enriched groundwater seep areas at Brush Brook ‘G' watershed and Sleepers River Research Watershed in Vermont. The soils at both site are sandy loams and vegetation comprises of Northern hardwoods mainly sugar maple. Gross N transformation rates of the soils were measured using the 15N isotopic pool dilution method. Rates were variable but there were many instances of gross nitrification rates being higher in nearly-saturated seep soils compared with drier upland soils. Denitrification rates were calculated by measuring the change in the 15N of both N20 and N2 during the gross nitrification incubation. Both nitrification and denitrification were occurring in the same cores. Rates varied seasonally and in response to soil moisture. Thus the seeps may alternatively be sources or sinks for nitrate.
DE: 0330 Geochemical cycles (1030)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0483 Riparian systems (0744, 1856)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting