C and N availability affects the 15N natural abundance of the soil microbial biomass across a cattle manure gradient

Paul Dijkstra, O. V. Menyailo, R. R. Doucett, S. C. Hart, Egbert Schwartz, Bruce A Hungate

Research output: Contribution to journalArticle

34 Scopus citations


The availability of C and N to the soil microbial biomass is an important determinant of the rates of soil N transformations. Here, we present evidence that changes in C and N availability affect the 15N natural abundance of the microbial biomass relative to other soil N pools. We analysed the 15N natural abundance signature of the chloroform-labile, extractable, NO3-, NH4+ and soil total N pools across a cattle manure gradient associated with a water reservoir in semiarid, high-desert grassland. High levels of C and N in soil total, extractable, NO3-, NH4+ and chloroform-labile fractions were found close to the reservoir. The δ15N value of chloroform-labile N was similar to that of extractable (organic + inorganic) N and NO3- at greater C availability close to the reservoir, but was 15N-enriched relative to these N-pools at lesser C availability farther away. Possible mechanisms for this variable 15N-enrichment include isotope fractionation during N assimilation and dissimilation, and changes in substrate use from a less to a more 15N-enriched substrate with decreasing C availability.

Original languageEnglish (US)
Pages (from-to)468-475
Number of pages8
JournalEuropean Journal of Soil Science
Issue number4
StatePublished - Aug 2006


ASJC Scopus subject areas

  • Soil Science
  • Earth-Surface Processes

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