Impacts of anthropogenic N additions on nitrogen mineralization from plant litter in exotic annual grasslands

Abby G. Sirulnik, Edith B. Allen, Thomas Meixner, Michael F. Allen

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Urban regions of southern California receive up to 45 kg N ha-1 y-1 from nitrogen (N) deposition. A field decomposition study was done using 15N-labelled litter of the widespread exotic annual grass Bromus diandrus to determine whether elevated soil N is strictly from N deposition or whether N mineralization rates from litter are also increased under N deposition. Tissue N and lignin concentrations, which are inversely related in field sites with high and low N deposition, determine the rate at which N moves from plant litter to soil and becomes available to plants. The effect of soil N on N movement from litter to soil was tested by placing litter on high and low N soil in a factorial experiment with two levels of litter N and two levels of soil N. The litter quality changes associated with N deposition resulted in faster rates of N cycling from litter to soil. Concentrations of litter-derived N in total N, NH4+, NO3-, microbial N and organic N were all higher from high N/low lignin litter than from low N/high lignin litter. Litter contributed more N to soil NH4+ and microbial N in high N than low N soil. At the end of the study, N mineralized from high N litter on high N soil accounted for 46% of soil NH4+ and 11% of soil NO3-, compared to 35% of soil NH4+ and 6% of soil NO3- from low N litter on low N soil. The study showed that in high N deposition areas, elevated inorganic soil N concentrations at the end of the summer N deposition season are a result of N mineralized from plant litter as well as from N deposition.

Original languageEnglish (US)
Pages (from-to)24-32
Number of pages9
JournalSoil Biology and Biochemistry
Issue number1
StatePublished - Jan 2007


  • Decomposition
  • Litter
  • Mineralization
  • Nitrogen
  • Stable isotope

ASJC Scopus subject areas

  • Microbiology
  • Soil Science


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