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NITROGEN SATURATION AND RETENTION IN FORESTED WATERSHEDS OF THE CATSKILL MOUNTAINS, NEW YORK
Author(s) -
Lovett Gary M.,
Weathers Kathleen C.,
Sobczak William V.
Publication year - 2000
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.1890/1051-0761(2000)010[0073:nsarif]2.0.co;2
Subject(s) - streams , hydrology (agriculture) , watershed , nitrogen , saturation (graph theory) , environmental science , nitrate , seasonality , deposition (geology) , environmental chemistry , groundwater , ecology , chemistry , geology , geomorphology , biology , geotechnical engineering , mathematics , organic chemistry , combinatorics , computer network , machine learning , sediment , computer science
The Catskill Mountains of southeastern New York receive relatively high rates of atmospheric N deposition, and NO 3 − concentrations in some streams have increased dramatically since the late 1960s. We measured the chemistry of 39 first‐ and second‐order streams with forested watersheds to determine the variability of nitrogen concentrations within the Catskill Mountain area. We found that some streams have low NO 3 − concentrations throughout the year, some have seasonal cycles of varying amplitude, and some have relatively high concentrations year round. If the concentration and seasonality of NO 3 − in stream water are used as indices of nitrogen saturation, then most stages of nitrogen saturation are evident in our survey of Catskill watersheds. Organic nitrogen was a small portion of the total nitrogen for streams with high NO 3 − concentration, but organic N was the dominant form of N (up to 73% of the total) in the streams with lowest nitrate. Estimated retention of N in these watersheds (based on total N in stream water) ranged from 49% to 90% of the atmospheric input. The variation in stream water NO 3 − concentration and the amplitude of the seasonal fluctuations did not appear to be attributable to differences among watersheds in atmospheric deposition, watershed topography, or groundwater influx to the stream. We hypothesize that differences among watersheds in forest species composition and forest history, which are interrelated, produce most of the variation in NO 3 − concentration that we observed.