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TECHNICAL REPORTS

Landscape and Watershed Processes

Upland Disturbance Affects Headwater Stream Nutrients and Suspended Sediments during Baseflow and Stormflow

^a Oak Ridge National Laboratory, Bethel Valley Road, P.O. Box 2008, Oak Ridge, TN 37831-6036
^b Department of Biological Sciences, 331 Funchess Hall, Auburn University, Auburn, AL 36849-5407

^* Corresponding author (Jhouser{at}usgs.gov)

Received for publication March 18, 2005. Because catchment characteristics determine sediment and nutrient inputs to streams, upland disturbance can affect stream chemistry. Catchments at the Fort Benning Military Installation (near Columbus, Georgia) experience a range of upland disturbance intensities due to spatial variability in the intensity of military training. We used this disturbance gradient to investigate the effects of upland soil and vegetation disturbance on stream chemistry. During baseflow, mean total suspended sediment (TSS) concentration and mean inorganic suspended sediment (ISS) concentration increased with catchment disturbance intensity (TSS: R² = 0.7, p = 0.005, range = 4.0–10.1 mg L^–1; ISS: R² = 0.71, p = 0.004, range = 2.04–7.3 mg L^–1); dissolved organic carbon (DOC) concentration (R² = 0.79, p = 0.001, range = 1.5–4.1 mg L^–1) and soluble reactive phosphorus (SRP) concentration (R² = 0.75, p = 0.008, range = 1.9–6.2 µg L^–1) decreased with increasing disturbance intensity; and ammonia (NH₄⁺), nitrate (NO₃^–), and dissolved inorganic nitrogen (DIN) concentrations were unrelated to disturbance intensity. The increase in TSS and ISS during storms was positively correlated with disturbance (R² = 0.78 and 0.78, p = 0.01 and 0.01, respectively); mean maximum change in SRP during storms increased with disturbance (r = 0.7, p = 0.04); and mean maximum change in NO₃^– during storms was marginally correlated with disturbance (r = 0.58, p = 0.06). Soil characteristics were significant predictors of baseflow DOC, SRP, and Ca²⁺, but were not correlated with suspended sediment fractions, any nitrogen species, or pH. Despite the largely intact riparian zones of these headwater streams, upland soil and vegetation disturbances had clear effects on stream chemistry during baseflow and stormflow conditions.

Abbreviations: BC1 and BC2, tributaries of Bonham Creek • DIN, dissolved inorganic nitrogen (NH₄⁺ + NO₃^–) • DOC, dissolved organic carbon • HB, Hollis Branch Creek • ISS, inorganic suspended sediment • KM1 and KM2, tributaries of Kings Mill Creek • LC, Lois Creek • LPK, tributary of Little Pine Knot Creek • OSS, organic suspended sediment • SB2, SB3, and SB4, tributaries of Sally Branch • SRP, soluble reactive phosphorus • TSS, total suspended sediment