How external and internal nutrient supplies affects wild rice shoot and root litter
decomposition and the nitrogen (N) and phosphorus (P) dynamics in decaying litter were
examined in two experiments. In a site quality experiment, wild rice shoot and root
litterbags were decayed in mesocosms in the field with added N or P or a control as
ambient conditions, over 115 days. In the second litter quality experiment, wild rice
plants were grown with N, P, both, or none, to produce litter of different qualities and
then decayed for 168 days under controlled temperature in the laboratory. The impacts of
both site and litter quality was greater on shoot litter than root litter. In the site quality
experiment, P addition significantly increased wild rice shoot decay more than N addition
and reduced P mineralization over time compared to the control. Neither adding N nor P
influenced root decay, but adding P increased root P immobilization compared to the
control, and the effect was much greater in root litter compared to shoot litter. In the litter
quality experiment, P enrichment increased litter quality by increasing P concentrations
and water-soluble compound concentrations in shoot litter and decreasing lignin
concentrations in root litter, thereby increasing decay rates of both shoot and roots,
although, the impact was much greater on shoot decay. N enrichment increased plant
growth but reduced shoot litter quality and decay likely because these larger plants had
greater lignin concentrations for structural support and lower phosphorus concentrations
and lower N:P ratios. Increased lignin likely overrides a concomitant increase in nitrogen
concentration in shoot litter and appears to control wild rice decomposition. Initial
lignin:P,C:P, lignin+asid-solubles:P and the N:P ratios of shoot litter were correlated to the final mass remaining. Lignin and phosphorus appear to play a key role in driving wild
rice decay through the opposite effects that each have on litter quality.
University of Minnesota M.S. dissertation. February 2011. Major: Integrated biosciences. Advisor: John Joseph Pastor. 1 computer file (PDF); vi, 56 pages, appendix p. 53-56.
Hildebrandt, Lauren R..
Effects of external and internal nutrient supplies on decomposition of wild rice, Zizania palustris..
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