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Pretreatment of Wood for Measuring Tree-Ring Nitrogen

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. Dendrochemistry of Nitrogen. Can ring-N elucidate N availability of the past? N mobility (sap chemistry)

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Pretreatment of Wood for Measuring Tree-Ring Nitrogen

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  1. Pretreatment of Wood forMeasuring Tree-Ring Nitrogen Paul R. Sheppard Lab. of Tree-Ring Research and Mary A. Topa Boyce Thompson Inst. Plant Research

  2. 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 …”

  3. 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?

  4. Wood Treatments • Chemical Treatments • Organic solvents • Oxidizers • Reducers • Physical Treatments • Autoclaving • Microwaving • Pulverizing

  5. Study Details • 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?

  6. 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

  7. 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

  8. N Content of Cells • 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?

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