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Nitrogen Dynamics of 15 N-Labeled Decomposing Fine Roots in Western Oregon Forests

Nitrogen Dynamics of 15 N-Labeled Decomposing Fine Roots in Western Oregon Forests. Tiffany van Huysen, Dr. Mark Harmon, and Dr. Steve Perakis Department of Forest Science March 5, 2004. Outline of Presentation. Introduction Research Questions Research Design and Methods Impacts of 15 N

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Nitrogen Dynamics of 15 N-Labeled Decomposing Fine Roots in Western Oregon Forests

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  1. Nitrogen Dynamics of 15N-Labeled Decomposing Fine Roots in Western Oregon Forests Tiffany van Huysen, Dr. Mark Harmon, and Dr. Steve Perakis Department of Forest Science March 5, 2004

  2. Outline of Presentation • Introduction • Research Questions • Research Design and Methods • Impacts of 15N • Summary

  3. Nitrogen Release from Litter 100 Fine Roots Aboveground Litter % Ash-free Mass Remaining 10 1 2 3 % Nitrogen

  4. Research Questions 1. How does the relationship between mass loss and N dynamics differ between aboveground litter and fine roots? 2. What is the fate of 15N released from decomposing litter?

  5. Methods • Field decomposition time series study • 2 ½ years • Fate of 15N analysis study • 2 years • Both studies will be conducted at Cascade Head and H.J. Andrews Experimental Forests

  6. 200-year Log Decomposition Experiment sites physically adjacent to the placement of the ongoing Root Decomposition Experiment of Chen Hua and the Fine Wood Decomposition Experiment of Mark Harmon Site 1 Site 2 Site 3 H.J. Andrews Plots

  7. 501 Field Decomposition Time Series Study • Litterbag technique • Mesh, cloth/mesh, cloth • 5 grams air-dried litter • 1080 litterbags total • 540 bags per site • Subsamples of litter retained for initial chemical analysis and moisture content

  8. Experimental Design for Time Series Study Western Oregon Cascade Head H.J. Andrews Plot 1 Plot 2 Plot 3 Plot 1 Plot 2 Plot 3 Rep 1 Rep 1 Rep 1 Rep 1 Rep 1 Rep 1 Rep 2 Rep 2 Rep 2 Rep 2 Rep 2 Rep 2

  9. 1 2 3 4 5 6 7 Layout for Litterbags, 1 Replicate 10 m 10 m = mesh or cloth/mesh = cloth

  10. Up Close with a Litterbag Line 1 meter R T N R T N R T L Douglas-fir Sitka spruce bigleaf maple R = roots T = twigs N = needles L = leaves

  11. R R R C R T N/L R R R R R R Fate of 15N Study Randomized Complete Block design with 3 treatments and a control C = control R = roots T= twigs N/L= needles/leaves Each circle = 1 planted seedling

  12. 5% 99% 0.3705 0.4562 Plants Nitrogen Sink 0.3667 0.3753 Ecosystem Potential Impact of Adding 15N-Enriched Plant Material to the Sites Background = 0.3663 atom% 15N Ecosystem N stock = 4930 kg N ha-1 (Sollins et al. 1980) Plant N stock = 493 kg N ha-1 Addition rate = 0.45 kg N ha-1 Plants receive 15% of N addition Enrichment

  13. 0.3667 0.3691 0.3705 0.3691 0.3667 0.3775 0.3775 0.3775 0.3691 0.3691 0.3775 0.3775 0.3705 0.3705 0.3775 0.3775 0.3775 0.3691 0.3691 0.3667 0.3691 0.3705 0.3691 0.3667 Dilution of Tracer Background = 0.3663 atom% 15N Enrichment = 99% 0.4562

  14. 0.3663 0.3664 0.3665 0.3664 0.3663 0.3668 0.3668 0.3668 0.3664 0.3664 0.3668 0.3668 0.3665 0.3665 0.3668 0.3668 0.3668 0.3664 0.3664 0.3663 0.3664 0.3665 0.3664 0.3663 Dilution of Tracer Background = 0.3663 atom% 15N Enrichment = 5% 0.3705

  15. Summary • Nitrogen dynamics of fine root decomposition with aboveground litter as a comparison • Fate of 15N released from decomposing litter • Field decomposition time series study • Fate of 15N analysis study

  16. Questions?

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