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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Disturbance Ecology IV
STREAM METABOLISM AND STORMFLOW CHEMISTRY: PATTERNS ALONG A GRADIENT OF UPLAND DISTURBANCE.
J.N. Houser and P.J. Mulholland. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6036
Because watershed characteristics affect the inputs of sediments and nutrients into streams, watershed disturbances can affect in-stream processes. We examined the effect of upland disturbance on stream chemistry (i.e. suspended sediments and nutrients) under baseflow and stormflow conditions, and on in-stream metabolism. Spatial variability in the intensity of military training (infantry and tank maneuvers) at the Ft. Benning military base (Columbus, GA) results in some stream catchments being highly disturbed while others remain relatively pristine. We selected 11 stream sites located in 11 different catchments: 3 reference sites, 4 sites of low to moderate disturbance, and 4 sites of high disturbance. Summer baseflow chemistry and suspended sediments did not show strong trends among the different disturbance intensities. However, during storm events, larger increases in suspended sediments (standardized to the magnitude of the increase in stream flow and baseflow concentrations) occurred in the disturbed sites compared to the reference sites. During the summer, rates of in-stream respiration were higher in the reference systems (2 - 4 g m-2 d-1), and lower in the highly disturbed systems (~0 - 1.5 g m-2 d-1), suggesting that biological activity may be reduced in streams in disturbed watersheds.
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