Nitrogen dynamics in stream and soil waters

Abstract

The mountainous riparian corridor performs important hydrologic functions including nutrient transfers between the terrestrial (upslope) and aquatic (stream) ecosystems. Nitrate-nitrogen and ammonium-nitrogen concentrations were determined on water samples collected in 1993 and 1994 from a montane riparian zone in Northern Colorado. Soil water samples were collected from the riparian corridor and upslope systems, under both losing (summer reservoir releases) and gaining (spring snowmelt runoff) streamflow conditions. Statistical analyses using least square means contrasts were made to identify spatial and temporal differences between: 1) the upslope system and the riparian corridor, 2) the upslope system and the stream, and 3) the riparian corridor and the stream. The Sheep Creek riparian corridor may serve as a sink for nitrate-nitrogen in both gaining and losing streamflow conditions, and as a source for ammonium nitrogen in gaining streamflow conditions. The length of the source or sink period is relatively short and is not meant to suggest differences in site productivity. Streamflow generation mechanisms help determine if the riparian corridor is a nutrient sink or source.