1. 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

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

3. Nitrogen Release from Litter % Ash-free Mass Remaining % Nitrogen 123 100 10 Fine Roots Aboveground Litter

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 15 N released from decomposing litter?

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

6. H.J. Andrews Plots 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 3 Site 2 Site 1

7. 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 501

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

9. Layout for Litterbags, 1 Replicate 1234567 = mesh or cloth/mesh= cloth 10 m

10. Up Close with a Litterbag Line 1 meter Douglas-firSitka sprucebigleaf maple RRRTTTNNL R = rootsT = twigsN = needlesL = leaves

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

12. Potential Impact of Adding 15 N-Enriched Plant Material to the Sites Enrichment Nitrogen Sink 5%99% Plants Ecosystem 0.3705 0.3667 0.4562 0.3753 Background = 0.3663 atom% 15 N 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

13. Dilution of Tracer 0.4562 0.3775 0.36670.36910.37050.36910.3667 0.3691 0.3705 0.3691 0.36670.36910.37050.36910.3667 Background = 0.3663 atom% 15 NEnrichment = 99%

14. Dilution of Tracer 0.3705 0.3668 0.36630.36640.36650.36640.3663 0.3664 0.3665 0.3664 0.36630.36640.36650.36640.3663 Background = 0.3663 atom% 15 NEnrichment = 5%

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

16. Questions?