Nitrogen biogeochemistry in a boreal headwater stream network in interior Alaska
Science of the Total Environment
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Abstract
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.
Suggested Citation
Smith, R.L., Repert, D.A., Koch, J.C., 2021, Nitrogen biogeochemistry in a boreal headwater stream network in interior Alaska: Science of the Total Environment, v. 764, 142906, 11 p., https://doi.org/10.1016/j.scitotenv.2020.142906.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Nitrogen biogeochemistry in a boreal headwater stream network in interior Alaska |
| Series title | Science of the Total Environment |
| DOI | 10.1016/j.scitotenv.2020.142906 |
| Volume | 764 |
| Year Published | 2021 |
| Language | English |
| Contributing office(s) | WMA - Earth System Processes Division |
| Description | 142906, 11 p. |
| Country | United States |
| State | Alaska |
| Other Geospatial | East Twin Creek, Nome Creek, West Twin Creek, White Mountains |