title: Carbon and nitrogen stoichiometry and nitrogen cycling rates in streams.
abstract: Stoichiometric 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.
authors.affiliation: Division of Biology, Kansas State University, Manhattan, KS 66506, USA. wkdodds@ksu.edu
authors.forename: Walter K
authors.initials: WK
authors.lastname: Dodds
authors.forename: Eugenia
authors.initials: E
authors.lastname: Martí
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Tank
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Pontius
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Hamilton
authors.forename: Nancy B
authors.initials: NB
authors.lastname: Grimm
authors.forename: William B
authors.initials: WB
authors.lastname: Bowden
authors.forename: William H
authors.initials: WH
authors.lastname: McDowell
authors.forename: Bruce J
authors.initials: BJ
authors.lastname: Peterson
authors.forename: H Maurice
authors.initials: HM
authors.lastname: Valett
authors.forename: Jackson R
authors.initials: JR
authors.lastname: Webster
authors.forename: Stan
authors.initials: S
authors.lastname: Gregory
mesh_terms: D002244:Carbon / Q000378:metabolism*; D017753:Ecosystem; D004784:Environmental Monitoring; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000032:analysis; D045483:Rivers
chemical_list: D009587:Nitrogen Isotopes; D002244:Carbon; D009584:Nitrogen