Nitrogen Dynamics of 15 N-Labeled Decomposing Fine Roots in Western Oregon Forests Tiffany van...
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Transcript of Nitrogen Dynamics of 15 N-Labeled Decomposing Fine Roots in Western Oregon Forests Tiffany van...
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
Outline of Presentation
Introduction Research Questions Research Design and Methods Impacts of 15N Summary
Nitrogen Release from Litter
% Ash-free Mass
Remaining
% Nitrogen
1 2 3
100
10
Fine RootsAboveground Litter
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?
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
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
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
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
Layout for Litterbags, 1 Replicate1 2 3 4 5 6 7
= mesh or cloth/mesh
= cloth
10 m
10 m
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
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
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
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%
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%
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
Questions?