Nitrogen biogeochemistry in a boreal headwater stream network in interior Alaska
April 10, 2021
High latitude, boreal watersheds are nitrogen (N)-limited ecosystems that export large amounts of organic carbon (C). Key controls on C cycling in these environments are the biogeochemical processes affecting the N cycle. A study was conducted in Nome Creek, an upland headwater tributary of the Yukon River, and two first-order tributaries to Nome Creek, to examine the relation between seasonal and transport-associated changes in C and N pools and N-cycling processes across varying hydrologic gradients using laboratory bioassays of water and sediment samples and in-stream tracer tests. DON exceeded dissolved inorganic nitrogen (DIN) in Nome Creek except late in the summer season, with little variation in organic C:N ratios with time or transport distance. DIN was dominant in the 1st order tributaries. Rates of organic N mineralization and denitrification in laboratory incubations were related to sediment organic C content, while nitrification rates differed greatly between two 1st order tributaries with similar drainages. Additions of DIN or urea did not stimulate microbial activity. In-stream tracer tests with nitrate and urea indicated that uptake rates were slow relative to transport rates; simulated rates of uptake in stream storage zones were higher than rates assessed in the laboratory bioassays. In general, N-cycle processes were more active and had a greater overall impact in the 1st order tributaries and were minimized in Nome Creek, the larger, higher velocity, transport-dominated stream. Understanding key controls on N-cycling processes in these watersheds has important implications for DIN speciation and down-stream impacts of potential increased N loads in response to climate warming.
Citation Information
Publication Year | 2021 |
---|---|
Title | Nitrogen biogeochemistry in a boreal headwater stream network in interior Alaska |
DOI | 10.1016/j.scitotenv.2020.142906 |
Authors | Richard L. Smith, Deborah A. Repert, Joshua C. Koch |
Publication Type | Article |
Publication Subtype | Journal Article |
Series Title | Science of the Total Environment |
Index ID | 70229985 |
Record Source | USGS Publications Warehouse |
USGS Organization | WMA - Earth System Processes Division |
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Nitrogen biogeochemistry in a boreal headwater stream network in Interior Alaska, 2008 to 2011
High latitude, boreal watersheds are nitrogen-limited ecosystems that export large amounts of organic carbon. Key controls on carbon cycling in these environments are the biogeochemical processes affecting the nitrogen cycle. This data release presents results of a 3-year field study from 2008-2011 to document the relation between seasonal and transport-associated changes in carbon and...
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Nitrogen biogeochemistry in a boreal headwater stream network in Interior Alaska, 2008 to 2011
High latitude, boreal watersheds are nitrogen-limited ecosystems that export large amounts of organic carbon. Key controls on carbon cycling in these environments are the biogeochemical processes affecting the nitrogen cycle. This data release presents results of a 3-year field study from 2008-2011 to document the relation between seasonal and transport-associated changes in carbon and...