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Drivers of nitrogen transfer in stream food webs across continents
Author(s) -
Norman Beth C.,
Whiles Matt R.,
Collins Sarah M.,
Flecker Alexander S.,
Hamilton Steve K.,
Johnson Sherri L.,
Rosi Emma J.,
Ashkenas Linda R.,
Bowden William B.,
Crenshaw Chelsea L.,
Crowl Todd,
Dodds Walter K.,
Hall Robert O.,
ElSabaawi Rana,
Griffiths Natalie A.,
Marti Eugènia,
McDowell William H.,
Peterson Scot D.,
Rantala Heidi M.,
Riis Tenna,
Simon Kevin S.,
Tank Jennifer L.,
Thomas Steven A.,
Schiller Daniel,
Webster Jackson R.
Publication year - 2017
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1002/ecy.2009
Subject(s) - ecology , environmental science , geography , nitrogen , earth science , oceanography , geology , biology , chemistry , organic chemistry
Studies of trophic‐level material and energy transfers are central to ecology. The use of isotopic tracers has now made it possible to measure trophic transfer efficiencies of important nutrients and to better understand how these materials move through food webs. We analyzed data from thirteen 15 N‐ammonium tracer addition experiments to quantify N transfer from basal resources to animals in headwater streams with varying physical, chemical, and biological features. N transfer efficiencies from primary uptake compartments (PUCs; heterotrophic microorganisms and primary producers) to primary consumers was lower (mean 11.5%, range <1% to 43%) than N transfer efficiencies from primary consumers to predators (mean 80%, range 5% to >100%). Total N transferred (as a rate) was greater in streams with open compared to closed canopies and overall N transfer efficiency generally followed a similar pattern, although was not statistically significant. We used principal component analysis to condense a suite of site characteristics into two environmental components. Total N uptake rates among trophic levels were best predicted by the component that was correlated with latitude, DIN:SRP, GPP:ER, and percent canopy cover. N transfer efficiency did not respond consistently to environmental variables. Our results suggest that canopy cover influences N movement through stream food webs because light availability and primary production facilitate N transfer to higher trophic levels.