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Episodic, seasonal, and annual export of atmospheric and microbial nitrate from a temperate forest
Author(s) -
Sabo Robert D.,
Nelson David M.,
Eshleman Keith N.
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl066758
Subject(s) - nitrate , watershed , base flow , hydrograph , environmental science , streamflow , streams , surface runoff , temperate climate , hydrology (agriculture) , seasonality , temperate forest , experimental forest , deposition (geology) , atmospheric sciences , ecology , drainage basin , geology , sediment , biology , geography , computer network , paleontology , cartography , geotechnical engineering , machine learning , computer science
It remains difficult to assess the timing and amount of atmospherically deposited and microbial nitrate (NO 3 ‐N Atm and NO 3 ‐N Micro , respectively) reaching streams. To elucidate temporal variation of NO 3 ‐N Atm and NO 3 ‐N Micro , we measured nitrate concentrations, δ 17 O‐NO 3 − , and δ 18 O‐NO 3 − in a stream draining a gaged, forested watershed in the central Appalachian Mountains throughout a range of hydrological conditions during two water years. From the isotopic data we calculated Δ 17 O‐NO 3 − values, which were used to calibrate a statistical load model to estimate export of NO 3 ‐N Atm and NO 3 ‐N Micro . A hydrograph separation was used to estimate loss of NO 3 ‐N Atm and NO 3 ‐N Micro through base flow and direct runoff pathways. NO 3 ‐N Atm contributed 7–11% of the total nitrate yields and paralleled seasonal patterns of NO 3 ‐N Micro . Yields of NO 3 ‐N Atm and NO 3 ‐N Micro in streamflow during the study period were dominated (61 and 85%, respectively) by base flow transport, suggesting that base flow is a major loss pathway for both nitrate species from this watershed.