Nitrogen Dynamics of 15 N-Labeled Decomposing Fine Roots in Western Oregon Forests
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Transcript of Nitrogen Dynamics of 15 N-Labeled Decomposing Fine Roots in Western Oregon Forests
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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
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Outline of Presentation
Introduction Research Questions Research Design and Methods Impacts of 15N Summary
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Nitrogen Release from Litter
% Ash-free Mass
Remaining
% Nitrogen
1 2 3
100
10
Fine RootsAboveground Litter
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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?
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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
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H.J. Andrews Plots200-year Log Decomposition Experiment sitesphysically 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
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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
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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 2
Rep 1
Rep 2
Rep 1
Rep 2
Rep 1Rep 1
Rep 2 Rep 2Rep 2
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Layout for Litterbags, 1 Replicate1 2 3 4 5 6 7
= mesh or cloth/mesh
= cloth
10 m
10 m
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Up Close with a Litterbag Line
1 meter
Douglas-fir
Sitka spruce
bigleaf maple
R RR TT T NN L
R = roots
T = twigs
N = needles
L = leaves
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Fate of 15N 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
R R
R
R R
R
R
Each circle = 1 planted seedling
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Potential Impact of Adding 15N-Enriched Plant Material to the Sites
Enrichment
Nit
rog
en
S
ink
5% 99%
Plants
Ecosystem
0.3705
0.3667
0.4562
0.3753
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
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Dilution of Tracer
0.4562
0.37750.37750.3775
0.37750.3775
0.37750.37750.3775
0.36670.36910.37050.36910.3667
0.36910.3691
0.37050.3705
0.36910.3691
0.36670.36910.37050.36910.3667
Background = 0.3663 atom% 15N Enrichment = 99%
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Dilution of Tracer
0.3705
0.36680.36680.3668
0.36680.3668
0.36680.36680.3668
0.36630.36640.36650.36640.3663
0.36640.3664
0.36650.3665
0.36640.3664
0.36630.36640.36650.36640.3663
Background = 0.3663 atom% 15N Enrichment = 5%
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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
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Questions?