Tuesday, June 5, 2007

Organic C and N transport distances in tall-grass prairie streams

Jonathan M. O'Brien, Kellogg Biological Station, Michigan State University, 3700 East Gull Lake Drive, Hickory Corners, MI 49060, Walter K. Dodds, Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506, and Kymberly C. Wilson, Global Institute of Sustainability, Arizona State University, Tempe, AZ 85287.

We used field measurement and estimates of nitrogen (N) mineralization to calculate organic carbon (C) and organic N spiral lengths in four headwater prairie streams. Organic C spiraling was calculated from total benthic C, flux of dissolved and suspended C, and rate of respiration within the stream channel. Organic N spiraling was similarly calculated from benthic organic N, flux of dissolved and suspended N, and estimated rate of N mineralization. Spiral lengths for organic N (240 m to 2656 m) were approximately 10-fold that of organic C (24 m to 400 m) in most of the prairie streams. Total spiral length, or average distance between mineralization events, was calculated as the sum of inorganic and organic N spirals, and ranged from 260 m to 2830 m. The degree of similarity, or coupling, between organic N and organic C transport distances was regulated by the degree of biotic N limitation.  The dominance of organic N, relative to inorganic N, both in terms of total N concentration and transport distance make organic N extremely important in the overall transport of N in this system.