Pretreatment of Wood for Measuring Tree-Ring Nitrogen Paul R. Sheppard Lab. of Tree-Ring Research...
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Pretreatment of Wood for Measuring Tree-Ring Nitrogen Paul R. Sheppard Lab. of Tree-Ring Research and Mary A. Topa Boyce Thompson Inst. Plant Research
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Transcript of Pretreatment of Wood for Measuring Tree-Ring Nitrogen Paul R. Sheppard Lab. of Tree-Ring Research...
Pretreatment of Wood
for
Measuring Tree-Ring Nitrogen
Paul R. SheppardLab. of Tree-Ring Research
andMary A. Topa
Boyce Thompson Inst. Plant Research
Dendrochemistry of Nitrogen• Can ring-N elucidate N availability of
the past?
• N mobility (sap chemistry)
– Poulson et al. (1995): “N concentration variation in tree rings cannot provide information on past environmental availability of N …”
What If Wood Is “Cleaned”?
• Heartwood extractives: No N, but mass
• Sapwood: Sap has organic N compounds
• Cell walls have N
– Does this component reflect N availability at time of ring formation?
Wood Treatments
• Chemical Treatments– Organic solvents– Oxidizers– Reducers
• Physical Treatments– Autoclaving– Microwaving– Pulverizing
• Loblolly pine of North Carolina• 6-year-old trees in 2001• All trees N fertilized every year• Some trees 15N enriched in their 5th
year (1999)• Other trees left at natural abundance• Pre-enriched δ15N = natural
abundance?
Study Details
-100
0
100
200
300
400
500
1995 1996 1997 1998 1999 2000
delta
15N
(‰
)date of 15N fertilizationnonenriched--no treat (-1)enriched--no treat (+214)enriched--chemical (+38)enriched--physical & chemical (+18)
0.00
0.04
0.08
0.12
0.16
1995 1996 1997 1998 1999 2000
N C
onte
nt (
%)
nonenriched--no treat (0.11)enriched--no treat (0.12)enriched--chemical (0.05)enriched--physical & chemical (0.05)
Conclusions (so far)
• Measuring ring N right out of tree could be problematic– either δN or N content
• Combination of physical-chemical wood pretreatments works well – eliminate sap/cytoplasmic N
compounds
Can We Do Better?
• Pre-enriched δN (+18) not quite natural abundance
• Some other physical/chemical treatment?
• Parenchyma effect?– Fiber separation?– Ring N content of 0.01%, too low
• Hangarter (web notes):– “extensin produced is dependent
on mechanical wounding, infection”
• Cowling and Merrill (1966):– “N content of cambial zone varies
with … nutritional status …”– Extend to tracheids of tree rings?
N Content of Cells
0.00
0.02
0.04
0.06
0.08
0.10
0.12
1961-1965
1966-1970
1971-1975
1976-1980
1981-1985
1986-1990
1991-1995
1996-2001
N C
onte
nt (%
)no fert, no treat 400#/ac, no treat
pre fert avg = 0.06
pre fert avg = 0.06
post fert avg = 0.08
post fert avg = 0.07
