Kopaska, J. A.. Iowa State University, jkopaska@iastate.edu
Menzel, B. A.. Iowa State University, bmenzel@iastate.edu
Downing, J. A.. Iowa State University, downing@iastate.edu

Intensive agricultural land use has altered stream ecosystem processes in former tallgrass prairie areas of North America. This study sought to determine how land use practices affect nutrient export by streams in a landscape typical of the Corn Belt region of the United States. The thirteen first order streams and their watersheds studied represented land uses including row-crop agriculture, woodlands, pastures, and ungrazed grasslands. GIS analysis was employed to categorize land use within each watershed, including that of riparian areas. Instream physical features were measured and stream water quality assessed from biweekly water collections. Watersheds and streams were placed into land use groups using principal components analysis. Most watershed variation was explained by area, topography, and riparian conditions. Strong relationships existed between agricultural land use in the riparian zone, instream physical features, and nutrient export. Nutrient concentrations in stream flow were extremely high, ranging from 14 to 1400 uM/L of nitrogen (N) and 0.29 to 24 uM/L of phosphorus (P). Although P export did not vary significantly among land use groups, N export varied greatly reaching levels as high as 15.7 kg/ha/day in predominantly row-cropped watersheds. Riparian management in these watersheds is important in determining the rate and stoichiometry of stream nutrient export.
Day: Tuesday, Feb. 2
Time: 11:00 - 11:15am
Location: Sweeney Center
Code: SS07TU1100S