price c. mclemore iii, lisa j. samuelson, greg l. somers school of forestry and wildlife sciences

Relationship between hydraulic Relationship between hydraulic pathway length and foliar isotopic pathway length and foliar isotopic

carbon composition in longleaf pinecarbon composition in longleaf pine

Price C. McLemore III, Lisa J. Samuelson,Price C. McLemore III, Lisa J. Samuelson,Greg L. SomersGreg L. Somers

School of Forestry and Wildlife SciencesSchool of Forestry and Wildlife SciencesAuburn UniversityAuburn University, AL 36849, AL 36849

Hydraulic Resistance HypothesisHydraulic Resistance Hypothesis

• Hydraulic Limits to Tree Height and Tree Hydraulic Limits to Tree Height and Tree Growth (Ryan and Yoder, 1997)Growth (Ryan and Yoder, 1997)

• Maintenance Respiration and Stand Maintenance Respiration and Stand Development in a Subalpine Lodgepole Pine Development in a Subalpine Lodgepole Pine Forest (Ryan and Waring, 1992) Forest (Ryan and Waring, 1992)

• Foliar isotopic carbon discrimination Foliar isotopic carbon discrimination decreases with increased total hydraulic decreases with increased total hydraulic pathway lengthpathway length

ObjectivesObjectives

• Compare physiological functions and branch and Compare physiological functions and branch and tuft morphology between younger and older tuft morphology between younger and older longleaf pine treeslongleaf pine trees

• Establish a relationship between branch physiology Establish a relationship between branch physiology and branch morphologyand branch morphology

Methods, FieldMethods, Field

• Two sites Two sites

• Sampling in May and NovemberSampling in May and November

• 1-3 branches per tree sampled, > 5 1-3 branches per tree sampled, > 5 trees/site trees/site

• Branches with varying morphology, Branches with varying morphology, branching hierarchy, and agebranching hierarchy, and age

MethodsMethods

• Pathway lengths ranged up to 21mPathway lengths ranged up to 21m

• Tree heights ranged from grass stage to 23mTree heights ranged from grass stage to 23m

• Sampled branch heights ranged up to 20mSampled branch heights ranged up to 20m

• Branch lengths up to 7mBranch lengths up to 7m

• Tree Diameters ranged from 5 to 75cmTree Diameters ranged from 5 to 75cm

Methods, LabMethods, Lab

• Branch morphology measurementsBranch morphology measurements

– Diameters and lengths for each section or nodeDiameters and lengths for each section or node

– Branch orderBranch order

• Needle measurementsNeedle measurements

– needle length, age, projected area, dry weightneedle length, age, projected area, dry weight

• 13C most recent fully developed needles13C most recent fully developed needles

Hydraulic PathwayHydraulic Pathway

-31

-30

-29

-28

-27

-26

-25

-24

0 5 10 15 20 25

RR22=.813 p<0.001=.813 p<0.001

Total Length (m)Total Length (m)Site 1Site 1

C1

3 (

per

mill

)C

13 (

per

mill

)

Hydraulic PathwayHydraulic Pathway

-31

-30

-29

-28

-27

-26

-25

0 5 10 15 20 25

RR22=.782 p<0.001=.782 p<0.001

Site 2Site 2 Total Length (m)Total Length (m)

C1

3 (

per

mill

)C

13 (

per

mill

)

Microclimate EffectsMicroclimate Effects

2

4

6

8

10

12

14

0 5 10 15 20 25

Total Length (m)Total Length (m)

N (

mg

gN

(m

g g

-1-1))

p=.186p=.186

Site 1Site 1

Microclimate EffectsMicroclimate Effects

2

4

6

8

10

12

14

0 5 10 15 20 25

Total Length (m)Total Length (m)

N (

mg

gN

(m

g g

-1-1))

Site 2Site 2

RR22=.326 p=.007=.326 p=.007

Branch ComparisonsBranch Comparisons

-29

-28

-27

-26

-25

0 0.5 1 1.5 2

Site 1, hts (m)=15.2,15.7,15.5,15.7Site 1, hts (m)=15.2,15.7,15.5,15.7

C1

3 (

per

mill

)C

13 (

per

mill

)

Length (m)Length (m)

Y= -25.95B -28.06C+0.437X Y= -25.95B -28.06C+0.437X RR22=.88 =.88 p=.035p=.035


2

4

6

8

10

12

14

0 0.5 1 1.5 2


N (

mg

gN

(m

g g

-1-1))

Site 1Site 1

p=.194p=.194


-30

-29

-28

-27

-26

-25

0 1 2 3 4


C1

3 (

per

mill

)C

13 (

per

mill

)

Site 2, hts (m)=14.2,14.3,14.4,14.9Site 2, hts (m)=14.2,14.3,14.4,14.9

Y=-27.7A -28.9C +.546X Y=-27.7A -28.9C +.546X RR22=.760 =.760 p=.001p=.001


2

4

6

8

10

12

14

0 1 2 3 4

Length (m)Length (m)Site 2Site 2

N (

mg

gN

(m

g g

-1-1))

Y= 8.89A+7.96B+.388X Y= 8.89A+7.96B+.388X R R22=.269 =.269 p=.001p=.001

ConclusionsConclusions

• Significant linear relationships between Significant linear relationships between C13 and C13 and total hydraulic pathway length or branch length. total hydraulic pathway length or branch length.

• Microclimate effects are non-significant or Microclimate effects are non-significant or minimalminimal

• Increasing hydraulic resistance with increasing Increasing hydraulic resistance with increasing length of the hydraulic pathway may increase length of the hydraulic pathway may increase stomatal limitation of photosynthesis.stomatal limitation of photosynthesis.

Analyses Under Consideration:Analyses Under Consideration:

• Needle LengthNeedle Length

• Tuft Dry WeightTuft Dry Weight

• Projected Needle AreaProjected Needle Area

• Area to Weight RatioArea to Weight Ratio

• Specific Leaf AreaSpecific Leaf Area

• Non-Linear Regression for Non-Linear Regression for C13C13

• Total Hydraulic Pathway Volume (sapwood Total Hydraulic Pathway Volume (sapwood and total)and total)

price c. mclemore iii, lisa j. samuelson, greg l. somers school of forestry and wildlife sciences

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