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Linking Landscape Characteristics and High Stream Nitrogen in the Oregon Coast Range: Red Alder Complicates Use of Nutrient Criteria
Author(s) -
Greathouse Effie A.,
Compton Jana E.,
Van Sickle John
Publication year - 2014
Publication title -
jawra journal of the american water resources association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.957
H-Index - 105
eISSN - 1752-1688
pISSN - 1093-474X
DOI - 10.1111/jawr.12194
Subject(s) - alder , watershed , environmental science , deciduous , nutrient , land cover , streams , hydrology (agriculture) , nitrate , range (aeronautics) , ecology , streamflow , land use , geography , biology , geology , drainage basin , computer network , materials science , geotechnical engineering , machine learning , computer science , composite material , cartography
Red alder ( A lnus rubra ), a nitrogen(N)‐fixing deciduous broadleaf tree, can strongly influence N concentrations in western O regon and W ashington. We compiled a database of stream N and GIS ‐derived landscape characteristics in order to examine geographic variation in N across the Oregon Coast Range. Basal area of alder, expressed as a percent of watershed area, accounted for 37% and 38% of the variation in summer nitrate and total N (TN) concentrations, respectively. Relationships between alder and nitrate were strongest in winter when streamflow and landscape connections are highest. Distance to the coast and latitude, potential surrogates for sea salt inputs, and watershed area were also related to nitrate concentrations in an all‐subsets regression analysis, which accounted for 46% of the variation in summer nitrate concentrations. The model with the lowest Akaike's Information Criterion did not include developed or agricultural land cover, probably because few watersheds in our database had substantial levels of these land cover classes. Our results provide evidence, at a regional scale, that background sources and processes cause many Coast Range streams to exceed proposed nutrient criteria, and that the prevalence of a single tree species (N‐fixing red alder) exerts a dominant control over stream N concentrations across this region.