Abstract
Leaching of excess nitrogen (N) to groundwater in fertilized landscapes can overwhelm natural biogeochemical processes and cause long-term eutrophication of aquatic systems. We investigated N fate and transport from an intensively managed short-rotation woody crop (Pinus taeda) plantation through the riparian zone of an intermittent, low-gradient blackwater stream. Fertilization of the P. taeda plantation on the uplands resulted in contamination of groundwater with nitrate concentrations between 0.9 and 1.9 mg N L−1. No corresponding increase in nitrate was observed in stream water or shallow groundwater in the riparian zone. Groundwater travel-time modeling predicted that N from near-stream, upland plantation areas should have reached streams during the monitoring period. Two years of measuring N species in well water in contrasting landscape positions (within the plantation, swale, riparian edge, forested hillslope, and valley), indicated rapid nitrate transformation and denitrification within the forested wetland valleys. Denitrification in the shallow groundwater system within the toeslopes and the riparian zone was estimated to have removed > 90% of nitrate. These results highlight the importance of riparian zones as pathways for the removal of N and for controlling downstream N loads.
| Original language | English |
|---|---|
| Pages (from-to) | 1-20 |
| Number of pages | 20 |
| Journal | Biogeochemistry |
| Volume | 166 |
| Issue number | 1 |
| DOIs | |
| State | Published - Oct 2023 |
Funding
This work was supported by the United States Department of Energy Bioenergy Technologies Office and the United States Forest Service—Savannah River Site Interagency Agreement DE-AI09-00SR22188. S. Raulerson was supported by the United States Department of Agricultural through a National Institute of Food and Agriculture AFRI Predoctoral Fellowship (2022-67011-36463/1028181). This material is based on work supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Bioenergy Technologies Office. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. Peter Groffman and Lisa Martel of the Cary Institute provided advice and guidance throughout the project and conducted the N2 and N2 O analysis. Andy Horcher and John Blake (retired) provided logistical and in-kind organizational support. Kevin Fouts, Nathan Melear, and Katie Lamp’l helped in sampling the 2ndyear of the project and in well installation and sample processing. Christopher Lewis, Nathan Melear, Wesley Gerrin, Tyler McIntosh, Gabriel William Dias Ferreira, and Fabio Henrique Silva Floriano de Toledo assisted in drill rig operation and in augering plantation soil samples. Seth Younger, Katie Lamp’l, and Jordan Horvieth assisted in the cryogenic extraction process. Dan Buhr assisted in the processing of N2 and N2 O data. Lori Sutter at UGA, and Allison Fortner, Jana Phillips, and Sarah Ottinger at ORNL conducted the water chemistry analysis. This manuscript has been co-authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).
Keywords
- Denitrification
- Nitrate
- Nitrogen removal
- Riparian buffer
- Southeastern US
- Streamside management zone