LINX: nitrogen uptake, retention, and cycling in stream ecosystems: an intersite 15N experiment.

• Format: Dataset
• Language: unknown
• Published: 2011
• Subjects: Coweeta; LTER; stream; intersite; nitrogen; stable isotope; 15N; Ball Creek; Weir; north slope; Alaska
• Online Access: http://hdl.handle.net/10255/dryad.9215; http://metacat.lternet.edu/knb/metacat/knb-lter-cwt.3038.3/xml

The LINX project was a cooperative study among 11 institutions comparing the dynamics of nitrogen in streams at 12 sites ranging from the North Slope of Alaska to Puerto Rico. The central hypothesis of this project was: The considerable variability among streams in uptake, retention, and cycling of nitrogen is controlled by key hydrologic, chemical, and metabolic characteristics that determine water retention, degree of nitrogen deficiency, and energy flow through food webs in stream ecosystems. We used simulation modeling, field tracer (15N) additions, and an intersite comparative approach to address this hypothesis.1.The field tracer additions were done at each site, beginning in November 1996 and completed in fall 1998. In the two weeks prior to each tracer addition, we made several measurements including: short-term injection of a conservative tracer to determine hydraulic characteristics of the stream; short-term injections of nutrients (NH4, NO3, PO4) to determine relative uptake lengths and potential nutrient deficiency; and pre-addition measurements of 15N in 15 significant stream food web components. The 15N (as 15NH4) addition lasted 42 days. During this addition period, stream components were sampled at 1, 7, 14, 21, 28, and 42 days. Also during this period, stream metabolism (primary production and respiration) was measured using the whole-stream oxygen method. After the 42 days, stream components were sampled at 7, 14, and 28 days, 3, 6, 9, and 12 months . Our protocols are described in a 32-page LINX manual.