Wednesday, June 6, 2007 - 11:15 AM
236

Land Use Influences the Spatio-Temporal Controls on Nitrification and Denitrification in Headwater Streams

Clay Arango and Jennifer L. Tank. Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556

The nitrogen (N) and carbon (C) cycles of headwater streams are coupled, and land use modifies these cycles by increasing N availability and removing riparian vegetation.  Headwater streams can influence downstream N flux, but despite the present dominance of anthropogenically-modified landscapes, research has focused on forested streams.  We quantified N transformation rates monthly for three years in 18 agricultural and urban streams (with and without riparian buffers) to examine how riparian vegetation influences nitrification and denitrification in anthropogenically-modified streams.  Agricultural streams had higher nitrification rates (rmANOVA, p=0.009), and nitrification was influenced by sediment C and C:N ratios, and stream temperature (multiple linear regression, R2=0.26, p<0.00001).  Denitrification rates did not differ among land uses, despite significant differences in nitrate, temperature, sediment organic matter, and stream-water DOC (MLR, R2=0.47, p<0.00001), which have previously been shown to control denitrification.  Substrate (N and C) availability for N transformations did not differ between buffered and unbuffered streams of similar land use, likely due to the confounding influence of tile-drainage effectively bypassing riparian zones.  In this study, land use influenced the delivery of substrates for N transformations and decreased the role of riparian zones on stream N cycling by simplifying the drainage network of headwater streams.

See more of Biogeochemistry III
See more of Contributed Sessions

See more of The NABS 55th Annual Meeting