Identifying Controls on Nitrate Sources and Flowpaths in a Forested Catchment Using a Hydropedological Framework

Abstract

Nitrogen export from catchments provides insight into the functioning of forested ecosystems. In this study, we evaluated where in the forest streamwater nitrate comes from, and how it gets to the stream. Because of the intensive instrumentation at our long-term ecological study site, the Hubbard Brook Experimental Forest, we were able to record differences in nitrogen production based on the topography. Compared to the soils near the stream, the soils below bedrock outcrops, higher uphill in the forest, produced more nitrate and were thus considered “hotspots” for nitrate production. Our study showed that the vast majority of nitrate (>80%) flowed out of the forest in stream water at times when streamflow was very high, which occurred only ∼15% of the time. At these times, the stream network—which expands and contracts depending on how much rain there is and how much water is moving downstream—connects the nitrate “hotspots” with the stream. Detailed information about nitrate source areas, like we produced in this study, will allow better assessment of long-term nitrogen status in forested catchments.

Citation

Pardo, L. H.; Green, M. B.; Bailey, S. W.; McGuire, K. J.; McDowell, W. H. 2022. Identifying Controls on Nitrate Sources and Flowpaths in a Forested Catchment Using a Hydropedological Framework. Journal of Geophysical Research: Biogeosciences. 127: e2020JG006140. 20 p. https://doi.org/10.1029/2020JG006140.