Donald S. Ross James B. Shanley Anna R. Yatzor Amninder J. Kaur 2016 <p>Groundwater seeps in upland catchments are often enriched relative to stream waters, higher in pH, Ca²⁺ and sometimes NO₃¯. These seeps could be a NO₃¯ sink because of increased denitrification potential but may also be ‘hotspots’ for nitrification because of the relative enrichment. We compared seep soils with nearby well-drained soils in two upland forested watersheds in Vermont that are sites of ongoing biogeochemical studies. Gross N transformation rates were measured over three years along with denitrification rates in the third year. Gross ammonification rates were not different between the seep and upland soils but gross nitrification rates were about 3 × higher in the seep soils. Net nitrification rates trended higher in the upland soils and NO₃¯ consumption (gross—net) was 8 times higher in the seep soils. The average denitrification rate for seep soils was about equal to the difference in NO₃¯ consumption between seep and upland soils, suggesting denitrification can make up the difference. Temporal variation in seep water NO₃¯ concentration was correlated with watershed outlet NO₃¯ concentration. However, it is not clear that in-seep processes greatly altered seep water NO₃¯ contribution to the streams. Seep soils appear to be hotspots of both nitrification and denitrification.</p> application/pdf 10.1007/s13157-016-0733-z en Springer Enriched groundwater seeps in two Vermont headwater catchments are hotspots of nitrate turnover article