02512nas a2200313   4500008004100000245007600041210006900117300001300186490000800199520160300207653001101810653002601821653001301847653001801860653001201878100001801890700001401908700001301922700001801935700001901953700001601972700001701988700001902005700001902024700001702043700001802060700001602078856010402094       2004                        eng d00aCarbon and nitrogen stoichiometry and nitrogen cycling rates in streams0 aCarbon and nitrogen stoichiometry and nitrogen cycling rates in   a458 -4670 v1403 aStoichiometric analyses can be used to investigate the linkages between N and C cycles and how these linkages influence biogeochemistry at many scales, from components of individual ecosystems up to the biosphere. N-specific NH4 + uptake rates were measured in eight streams using short-term 15N tracer additions, and C to N ratios (C:N) were determined from living and non-living organic matter collected from ten streams. These data were also compared to previously published data compiled from studies of lakes, ponds, wetlands, forests, and tundra. There was a significant negative relationship between C:N and N-specific uptake rate; C:N could account for 41% of the variance in N-specific uptake rate across all streams, and the relationship held in five of eight streams. Most of the variation in N-specific uptake rate was contributed by detrital and primary producer compartments with large values of C:N and small values for N-specific uptake rate. In streams, particulate materials are not as likely to move downstream as dissolved N, so if N is cycling in a particulate compartment, N retention is likely to be greater. Together, these data suggest that N retention may depend in part on C:N of living and non-living organic matter in streams. Factors that alter C:N of stream ecosystem compartments, such as removal of riparian vegetation or N fertilization, may influence the amount of retention attributed to these ecosystem compartments by causing shifts in stoichiometry. Our analysis suggests that C:N of ecosystem compartments can be used to link N-cycling models across streams.10acarbon10aCarbon:Nitrogen ratio10anitrogen10astoichiometry10astreams1 aDodds, W., K.1 aMarti, E.1 aTank, J.1 aPontius, J.L.1 aHamilton, S.K.1 aGrimm, N.B.1 aBowden, W.B.1 aMcDowell, W.H.1 aPeterson, B.J.1 aValett, H.M.1 aWebster, J.R.1 aGregory, S.  uhttp://knz.lternet.edu/content/carbon-and-nitrogen-stoichiometry-and-nitrogen-cycling-rates-streams