Sources of nitrogen to the riparian zone of a desert stream: Implications for riparian vegetation and nitrogen retention

John D. Schade, Eugenia Marti, Jill R. Welter, Stuart G. Fisher, Nancy Grimm

Research output: Contribution to journalArticlepeer-review

73 Scopus citations


Riparian zones effectively remove nitrogen (N) from water flowing through riparian soils, particularly in agricultural watersheds. The mechanism of N removal is still unclear, especially the role of vegetation. Uptake and denitrification are the two most commonly studied mechanisms. Retention of groundwater N by plant uptake is often inferred from measurements of N in net incremental biomass. However, this assumes other sources of N are not contributing to the N demand of plants. The purpose of this work was to investigate the relative importance of three sources of available N to riparian trees in a desert stream - input in stream water during floods, input during baseflow, and mineralization of N from soil organic matter. Two approaches were used; a mass balance approach in which the mass of available N from each source was estimated, and a correlational approach in which indexes of each source were compared to leaf N for individual willow trees. Total N from all sources was 396 kg ha-1 y-1, with 172 kg ha-1 y-1 from mineralization, 214 kg ha-1 y-1 from the stream during baseflow, and 9.6 kg ha-1 y-1 from floods. Leaf N was significantly related to N mineralization rates and flood inputs; it was not related to baseflow inputs. We conclude that mineralization is a major source of available N for willow trees, subsidized by input of N from floods. Baseflow inputs are most likely removed by rapid denitrification at the stream-riparian edge, while higher rates of flood supply exceed the capacity of this "filter".

Original languageEnglish (US)
Pages (from-to)68-79
Number of pages12
Issue number1
StatePublished - Jan 1 2002


  • Denitrification
  • Desert stream
  • N mineralization
  • Nitrogen retention
  • Plant uptake
  • Riparian zone

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Environmental Chemistry
  • Ecology


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