Document: KAT-3-76-23

Seasonal relations between hydrology and subsurface carbon inputs from a riparian meadow to a second-order stream.

DWIRE, K.A.*, J.B.KAUFFMAN and J.BROOKSHIRE

Oregon State University, Corvallis, OR 97331, USA ¹

Abstract:
Subsurface inputs of dissolved organic matter from riparian areas to streams are strongly influenced by seasonal hydrology, riparian vegetation and soils, and microbial processes. Our objectives were: (1) To characterize the hydrology of a riparian meadow; and (2) to estimate seasonal subsurface inputs of dissolved organic carbon (DOC) from the meadow to the stream. The study site (250 m by 80 m) borders an unconstrained reach of a second-order tributary to the Grande Ronde River, northeast Oregon (elevation 1320 m). We monitored water table elevation in a grid-like network of wells from spring 1997 to fall 1999, and found that subsurface flow was generally down valley and towards the stream. We also measured DOC in stream water and shallow ground water from a subset of wells located in three floodplain plant communities - wet, moist, and dry meadow. Concentrations of DOC in subsurface water were lowest during spring snowmelt (mean = 5.4; SD = 1.2 mg/l), when low water temperatures limited microbial activity, and highest during late summer at base flow (mean = 28.5; SD = 3.8 mg/l). Average concentrations of DOC in stream water ranged from 2.1 to 11.8 mg/l, and were highest following rain storms in fall. When adjusted for discharge, however, DOC levels in stream water were greatest during spring run-off, when much of the meadow was flooded. The role of meadows as sources of DOC may vary seasonally, depending on interactions among hydrology, soils, vegetation, and terrestrial and aquatic microbial processes.

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This abstract is being presented at: 1:30 PM in session:
Oral Session #49: Linkages Between Land and Streams.