An inter-biome comparison of stream network nitrate dynamics
Helton, Ashley McKendree
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A simulation model of stream network NO3 dynamics was developed to scale up measurements of stream-reach NO3 uptake in seven catchments. The model explained NO3 dynamics well in two of seven catchments, revealing inter-biome differences in drivers of in-stream NO3 dynamics. Where the model performed poorly, additional drivers included: spatial distribution of NO3 sources; hydrologic delivery pathways of NO3; surface water-groundwater exchange; downstream changes in geomorphology/flow; and variation in uptake. Where the model performed well, uptake was a stronger driver and the network removed a higher proportion of NO3 inputs in Kansas than in North Carolina. In both catchments, small streams removed a substantial proportion of total inputs and were efficient NO3 removers, whereas large streams removed more NO3 mass individually. This research highlights the importance of understanding the influence of hydrology, geomorphology and biology on in-stream NO3 dynamics in order to explain, predict and understand NO3 uptake across biomes.