Regional meteorological drivers and long term trends of winter-spring nitrate dynamics across watersheds in northeastern North America

This study evaluated the contribution of winter rain-on-snow (ROS) events to annual and seasonal nitrate (N-NO₃) export and identified the regional meteorological drivers of inter-annual variability in ROS N-NO₃ export (ROS-N) at 9 headwater streams located across Ontario, Canada and the northeaster...

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Published inBiogeochemistry Vol. 130; no. 3; pp. 247 - 265
Main Authors Crossman, Jill, Eimers, M. Catherine, Casson, Nora J., Burns, Douglas A., Campbell, John L., Likens, Gene E., Mitchell, Myron J., Nelson, Sarah J., Shanley, James B., Watmough, Shaun A., Webster, Kara L.
Format Journal Article
LanguageEnglish
Published Cham Springer Science + Business Media 01.11.2016
Springer International Publishing
Springer Nature B.V
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Summary:This study evaluated the contribution of winter rain-on-snow (ROS) events to annual and seasonal nitrate (N-NO₃) export and identified the regional meteorological drivers of inter-annual variability in ROS N-NO₃ export (ROS-N) at 9 headwater streams located across Ontario, Canada and the northeastern United States. Although on average only 3.3 % of annual precipitation fell as ROS during winter over the study period, these events contributed a significant proportion of annual and winter N-NO₃ export at the majority of sites (average of 12 and 42 %, respectively); with the exception of the most northern catchment, where total winter precipitation was exceptionally low (average 77 mm). In years with a greater magnitude of ROS events, the timing of the peak N-NO₃ export period (during spring melt) was redistributed to earlier in the year. Variability in ROS frequency and magnitude amongst sites was high and a generalised linear model demonstrated that this spatial variability could be explained by interactive effects between regional and site-specific drivers. Snowpack coverage was particularly important for explaining the site-specific ROS response. Specifically, ROS events were less common when higher temperatures eliminated snow cover despite increasing the proportion of winter rainfall, whereas ROS event frequency was greater at sites where sufficient snow cover remained. This research suggests that catchment response to changes in N deposition is sensitive to climate change; a vulnerability which appears to vary in intensity throughout the seasonally snow-covered temperate region. Furthermore, the sensitivity of stream N-NO₃ export to ROS events and potential shifts (earlier) in the timing of N-NO₃ export relative to other nutrients affect downstream nutrient stoichiometry and the community composition of phytoplankton and other algae.
ISSN:0168-2563
1573-515X
DOI:10.1007/s10533-016-0255-z