Investigation Of within-tree and between-site Resin Canal Variation in Radiata Pine

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Investigation Of within-tree and between-site
Resin Canal Variation in Radiata Pine

• Jun Li YANG, Geoff DOWNES, Fiona CHEN, Dave COWN

2
Overview

• Radiata pine is a softwood with resin canals.
• Resin blemishes cause significant
• Losses in some products.
• Factors affecting presence include
• Climate
• Insects, diseases
• Silviculture
• Genetics

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Objectives

• To understand within-tree resin canal variation
• To understand regional resin canal variation and
  site effects
• To investigate relationships between resin
  canals, external resin bleeding of standing trees
  and blemishes in wood samples

4
Introduction

• Resin characteristics occur naturally in
  softwoods
• Resin defects can cause significant losses in
  appearance grade products and are a problem in
  value-added processing of radiata pine
• Within- and between-tree variation in resin canal
  occurrence is poorly documented
• Site factors and links to stem resin bleeding
  and to internal blemishes are unknown

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Materials and methods

• Software was developed to assist resin canal
  quantification
• Capture measurements on scanned images of smooth
  transverse surfaces
• Count resin canal numbers
• Measure and record resin canal location within
  samples
• Measure and record growth ring width
• Measure resin canal sizes

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Method Development

• Developed on 25mm wide samples
• Determine if the small transverse surface
  represented by SilviScan samples (2mm wide radial
  strips) is adequate for describing resin canal
  occurrence within individual trees

25mm wide radial strip
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Materials Analyses

• Used new method to asses resin canals on samples
  from a regional trial
• 150, 2 mm wide SilviScan samples (15 sites, 10
  strips per site)
• Polish the transverse surface
• Quantified resin canal occurrence in each sample
  (frequency at 15 sites, resin canal size at 9
  sites)
• Data analysis (ANOVA) effect of site on resin
  canal frequency and size
• Compared with assessments of stem resin bleeding
  and resin blemishes from discs

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Count Resin Canals
2 mm wide strips
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Measure Resin Canal Sizes
2 mm wide strips
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Resin Canal Radial Frequency (Single site)

• Non area-weighted data
• Decrease from pith to cambium
• Vary between trees and between sites
• Within-tree (between-ring) variation is much
  greater than between-tree variation
• Positively related to ring width

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Resin Canal Size (Single site)

• Increase from pith to cambium
• Vary between trees and between sites
• Within-tree (between-ring) variation is much
  greater than between-tree variation
• Inversely related to ring width

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Resin Canal Frequency Across Sites (15)

• Mean area-weighted resin canal frequency per m2
• Significant differences between sites
• 80 difference between two extreme sites

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Resin Canal Sizes Across Sites (9)

• Significant differences between sites
• 30 difference between two extreme sites

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Resin Canal Frequency v.s. Resin Blemishes

• Area-weighted resin canal count (count / m2)
• Moderate relationship between resin canal
  frequency and resin blemishes (r2 0.54)
• Sites with very low resin canal count have low
  levels of blemishes
• Sites with high resin canal count are among
  highly-blemished sites

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Conclusions 1 Sampling

• A 2mm radial strip gives similar resin canal
  information (number and location of resin canals)
  to a 20-25mm wide radial strip in 90 of cases
• To detect annual changes in resin canal
  frequency, strips from 5-7 trees are required.
• To investigate site differences, at least 6 trees
  (one strip per tree) are needed per site

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Conclusions 2 Site Effect

• Resin canal frequency is positively associated
  with site temperature (r 0.7) and inversely
  associated with site elevation (r -0.6)
• Warmer and/or lower elevation sites tend to
  produce more resin canals
• Temperature appears to have a greater effect than
  site elevation
• Rainfall, soil fertility (C/N ratio) and latitude
  did not affect resin canal frequency

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Conclusions 3 - Resin Canal Relationships

• Resin canal frequency is not related to resin
  canal size, based on site means
• Positive relationship between resin canal
  frequency and ring width
• Inverse relationship between resin canal size and
  ring width
• Significant between-site differences in resin
  canal count and size

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Conclusions 4 Relationships with Other
Resinous Features

• Resin canal frequency is moderately associated
  with resin blemishes (r2 54), based on site
  means
• Resin canal count is weakly linked to external
  resin bleeding score, resin pockets and resinous
  patches

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Acknowledgements
This study was partly funded by the Wood Quality
Initiative (WQI).