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Nitrogen retention in the riparian zone of catchments underlain by discontinuous permafrost
Author(s) -
O'DONNELL JONATHAN A.,
JONES JEREMY B.
Publication year - 2006
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/j.1365-2427.2006.01535.x
Subject(s) - riparian zone , permafrost , groundwater , hydrology (agriculture) , environmental science , nitrate , groundwater flow , drainage basin , streams , denitrification , riparian buffer , geology , aquifer , nitrogen , ecology , chemistry , geography , oceanography , computer network , geotechnical engineering , cartography , organic chemistry , habitat , computer science , biology
Summary 1. Riparian zones function as important ecotones that reduce nitrate concentration in groundwater and inputs into streams. In the boreal forest of interior Alaska, permafrost confines subsurface flow through the riparian zone to shallow organic horizons, where plant uptake of nitrate and denitrification are typically high. 2. In this study, riparian zone nitrogen retention was examined in a high permafrost catchment (approximately 53% of land area underlain by permafrost) and a low permafrost catchment (approximately 3%). To estimate the contribution of the riparian zone to catchment nitrogen retention, we analysed groundwater chemistry using an end‐member mixing model. 3. Stream nitrate concentration was over twofold greater in the low permafrost catchment than the high permafrost catchment. Riparian groundwater was not significantly different between catchments, averaging 13 μ m overall. Nitrogen retention, measured using the end‐member mixing model, averaged 0.75 and 0.22 mmol N m −2 day −1 in low and high permafrost catchments, respectively, over the summer. The retention rate of nitrogen in the riparian zone was 10–15% of the export in stream flow. 4. Our results indicate that the riparian zone functions as an important sink for groundwater nitrate and dissolved organic carbon (DOC). However, differences in stream nitrate and DOC concentrations between catchments cannot be explained by solute inputs from riparian groundwater to the stream and differences between streams are probably attributable to deeper groundwater inputs or flows from springs that bypass the riparian zone.