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Price C. McLemore III, Lisa J. Samuelson, Greg L. Somers School of Forestry and Wildlife Sciences

Relationship between hydraulic pathway length and foliar isotopic carbon composition in longleaf pine. Price C. McLemore III, Lisa J. Samuelson, Greg L. Somers School of Forestry and Wildlife Sciences Auburn University , AL 36849.

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Price C. McLemore III, Lisa J. Samuelson, Greg L. Somers School of Forestry and Wildlife Sciences

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  1. Relationship between hydraulic pathway length and foliar isotopic carbon composition in longleaf pine Price C. McLemore III, Lisa J. Samuelson, Greg L. Somers School of Forestry and Wildlife Sciences Auburn University, AL 36849

  2. Relationship between hydraulic pathway length and foliar isotopic carbon composition in longleaf pine Price C. McLemore III, Lisa J. Samuelson, Greg L. Somers School of Forestry and Wildlife Sciences Auburn University, AL 36849

  3. Hydraulic Resistance Hypothesis • Hydraulic Limits to Tree Height and Tree Growth (Ryan and Yoder, 1997) • Maintenance Respiration and Stand Development in a Subalpine Lodgepole Pine Forest (Ryan and Waring, 1992) • Foliar isotopic carbon discrimination decreases with increased total hydraulic pathway length

  4. Objectives • Compare physiological functions and branch and tuft morphology between younger and older longleaf pine trees • Establish a relationship between branch physiology and branch morphology

  5. Methods, Field • Two sites • Sampling in May and November • 1-3 branches per tree sampled, > 5 trees/site • Branches with varying morphology, branching hierarchy, and age

  6. Methods • Pathway lengths ranged up to 21m • Tree heights ranged from grass stage to 23m • Sampled branch heights ranged up to 20m • Branch lengths up to 7m • Tree Diameters ranged from 5 to 75cm

  7. Methods, Lab • Branch morphology measurements • Diameters and lengths for each section or node • Branch order • Needle measurements • needle length, age, projected area, dry weight • d13C most recent fully developed needles

  8. Hydraulic Pathway dC13 (per mill) R2=.813 p<0.001 Total Length (m) Site 1

  9. Hydraulic Pathway dC13 (per mill) R2=.782 p<0.001 Total Length (m) Site 2

  10. Microclimate Effects N (mg g-1) p=.186 Total Length (m) Site 1

  11. Microclimate Effects N (mg g-1) R2=.326 p=.007 Total Length (m) Site 2

  12. Branch Comparisons dC13 (per mill) Y= -25.95B -28.06C+0.437X R2=.88 p=.035 Length (m) Site 1, hts (m)=15.2,15.7,15.5,15.7

  13. Branch Comparisons N (mg g-1) p=.194 Length (m) Site 1

  14. Branch Comparisons dC13 (per mill) Y=-27.7A -28.9C +.546X R2=.760 p=.001 Length (m) Site 2, hts (m)=14.2,14.3,14.4,14.9

  15. Branch Comparisons N (mg g-1) Y= 8.89A+7.96B+.388X R2=.269 p=.001 Length (m) Site 2

  16. Conclusions • Significant linear relationships between dC13 and total hydraulic pathway length or branch length. • Microclimate effects are non-significant or minimal • Increasing hydraulic resistance with increasing length of the hydraulic pathway may increase stomatal limitation of photosynthesis.

  17. Analyses Under Consideration: • Needle Length • Tuft Dry Weight • Projected Needle Area • Area to Weight Ratio • Specific Leaf Area • Non-Linear Regression for dC13 • Total Hydraulic Pathway Volume (sapwood and total)

  18. Analyses Under Consideration: • Needle Length • Tuft Dry Weight • Projected Needle Area • Area to Weight Ratio • Specific Leaf Area • Non-Linear Regression for dC13 • Total Hydraulic Pathway Volume (sapwood and total)

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