Effects of external and internal nutrient supplies on decomposition of wild rice, Zizania palustris

Lauren R. Hildebrandt, John Pastor, Brad Dewey

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

We examined effects of external supplies of nitrogen (N) and phosphorus (P) from the environment and internal supplies of N and P from within litter tissue on wild rice shoot and root litter decomposition and N and P dynamics. To investigate the effects of external supplies, wild rice shoot and root litterbags were decayed in mesocosms in the field over 115 days with either added N or P or a control in ambient conditions. To investigate the effects of the internal nutrient supply, wild rice plants were grown with added N, P, both N and P, or no supplemental nutrient, to produce enriched litters, which were then decayed for 168 days under controlled temperature in the laboratory. Both external and internal N and P supplies affected shoot litter decay more than decay of root litter. Increased external P supply significantly increased the rate of wild rice shoot decay and P mineralization but adding N had no effect on decay rates through time. Neither adding N nor P influenced root decay. Enrichment of P internally in the litter through fertilization increased the concentration of P (0.16%) and water-soluble compounds (28.7% WS) in shoot litter compared to control shoot litter (0.11% P, 19.8% WS), which likely caused the significant increase in shoot decay rates, particularly in the labile pool. In contrast, N enrichment not only increased plant growth but also increased lignin concentrations (7.5%) compared to control shoot litter (2.7% lignin) for added structural support. This significantly inhibited decay and nearly doubled the amount of mass remaining after 168 days (42.1% OM) when compared to control shoots (22.4% OM). Increased lignin likely overrides a concomitant increase in nitrogen concentration in shoot litter and appears to control wild rice decomposition. Lignin and phosphorus appear to play a key role in driving wild rice decay through the effects on litter quality.

Original languageEnglish (US)
Pages (from-to)35-43
Number of pages9
JournalAquatic Botany
Volume97
Issue number1
DOIs
StatePublished - Feb 2012

Bibliographical note

Funding Information:
This research was funded through a grant provided by the National Science Foundation Ecosystems Ecology Program . Thanks to the Fond du Lac Band of Lake Superior Ojibway for providing sediments, seeds and field support. Thanks to Marissa Garry and Josh Bednar for field and lab assistance.

Keywords

  • Emergent graminoid
  • Litter quality
  • Nitrogen
  • Nutrient immobilization
  • Phosphorus

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