Download NMR Investigations of Natural Organic Matter in Forest

NMR Investigations of Natural Organic Matter
in Forest Ecosystems
Chris E. Johnson
Dept. of Civil & Environmental Engineering
Syracuse University
Forest Ecosystem Analysis
NMR Applications in Forest Ecosystem Studies
1. Plant tissues:
− Wood quality
− Response to
environmental stress
− Litter quality
NMR Applications in Forest Ecosystem Studies
1. Plant tissues:
− Wood quality
− Response to
environmental stress
− Litter quality
2. Soil organic matter:
− Decomposition
− Accumulation and role
as microbial substrate
NMR Applications in Forest Ecosystem Studies
1. Plant tissues:
− Wood quality
− Response to
environmental stress
− Litter quality
2. Soil organic matter:
− Decomposition
− Accumulation and role
as microbial substrate
3. Aquatic organic matter:
− Similarity to soil organic matter
− Substrate for aquatic organisms
Maine
White Mountain
National
White
MountainForest
Hubbard Brook
Experimental Forest
National Forest
#
#
New
Hampshire
N
Northern Hardwood Forest
Plant Tissues – Wood and Bark
Spectral Integration
COOH/ O
Amide Aryl
Aryl C
O-Alkyl-C
Alkyl-C
Plant Tissues – In situ Decomposition
Sampling with replication
Replication is crucial for:
• Avoiding spurious conclusions
• Statistical hypothesis testing
 (CPMAS method may be the only viable option)
Plant Tissues – (Fresh) Beech Bark
Plant Tissues – Wood & Bark
NMR analysis of soils
Oa Horizon
Bh Horizon
Bs1 Horizon
250
200
150
100
50
Chemical Shift (ppm)
0
-50
Soils – Humification of Organic Matter
Soils – Humification of Organic Matter
Soil vs. Soil Solution
Soils
Soil Solutions
Oa Horizon
Bh Horizon
Bs1 Horizon
250
200
150
100
50
Chemical Shift (ppm)
0
-50
250
200
150
100
50
Chemical Shift (ppm)
0
-50
Contrasting Soil and Solution Composition:
% Aromatic C
W1
(uncut)
W5
(clear-cut)
Oa
Oa
12.6
14.3
9.8
14.6
Bh
Bh
16.8
10.8
Bs
14.9
15.5
Bs
20.2
14.7
20.7
13.7
Stream
15.1
19.4
Stream
Approaches to Quantification
1. Bloch Decay (i.e. Direct Polarization)
Approaches to Quantification
1. Bloch Decay (i.e. Direct Polarization)
Oa Horizon Soil
Approaches to Quantification
2. Spin (Ac)counting
Approaches to Quantification
3. Correction Factors (from VCT Experiments)
Oa Horizon Soil
Approaches to Quantification
4. Spectral Editing Approaches
a. Proton Spin
Relaxation
Editing (PSRE)
b. REstoration of
Spectra via TCH
and T One Rho
(T1rH) Editing
(RESTORE)
Conclusions
1. NMR analyses provide useful information for
ecological studies.

An ideal application for low-field instruments.
2. Replication is essential for most ecological
applications.


Replication means high sample numbers.
High sample numbers mean CPMAS may be the only viable option.
3. Limited quantitative reliability of the CPMAS method
is a problem.

Without reliable approaches to quantification, NMR will remain a
supportive technology in ecosystem science