1. F. Munalula; T. Seifert; C.B. Wessels
A method for the non-destructive determination of the knotty core sizes of standing Pinus patula trees, based on ring width assessments at breast height and the pruning history
Afternoon gentleman,
As you can see I’m involved in Solid Wood Processing Teaching and Research.
F. Munalula; T. Seifert; C.B. Wessels
Department of Forest and Wood Science
Stellenbosch University
South Africa
Department of Forest and Wood Science

2. Department of Forest and Wood Science
Background
Pruning of plantation pine trees destined for solid wood processing
4 years
7 years
9 years
28 years
Cunningham and Price, 1996
Department of Forest and Wood Science

3. Department of Forest and Wood Science
Motivation
Why is it important to know the size of the knotty core of the pruned section of a pine plantation tree?
± 65% of log value
(1) The most valuable part of the tree stem
Department of Forest and Wood Science

4. Department of Forest and Wood Science
Motivation
(2) Large variation exist in the knotty core sizes – which affects the value that can be extracted by processors
(Park, 2002)
Department of Forest and Wood Science

5. Department of Forest and Wood Science
Motivation
(3) Information on knotty core sizes can be used by growers and processors to optimise the value extraction from plantations:
- Log allocation decisions;
- Log pricing decisions;
- Production planning and optimisation;
- Silviculture planning and research.
Department of Forest and Wood Science

6. Concept to be evaluated
Tree ring measurements +
Pruning records
Increment core 1 2 3 4 5 7 6 8 9 10 12 11 13 14 15 16
Department of Forest and Wood Science

7. Department of Forest and Wood Science
Some previous work
Prediction of knotty defect core sizes using plantation records and growth models (Cunningham and Price, 1996);
Pruned Log Index – destructive testing of sub-sample of trees, New Zealand (Park, 1989; 2002; 2005);
Pre-Harvest Quality Assessment: destructive testing of sub-sample of trees (Price et al., 2002);
Measurement of diameter over stub after each pruning operation (Gosnell, 1987).
Department of Forest and Wood Science

8. Department of Forest and Wood Science
Objectives
To assess the practical applicability of the methodology developed to predict the knotty core sizes of standing Pinus patula trees;
To establish a suitable within-tree increment core sampling strategy;
To establish the variation of knotty core sizes in a typical pruned Pinus patula resource;
To evaluate some applications of knotty core data from standing trees.
Department of Forest and Wood Science

9. Department of Forest and Wood Science
Methodology
Sample material: 17 pruned Pinus patula compartments, Mpumulanga, South Africa;
10 trees / compartment = 170 trees, stratified sampling;
Discs removed at breast height and 6m and sawlog; 1m
2.1m
1.3m
2.3m 6m 7m
11m 0m
Pulping
log
Saw log
Department of Forest and Wood Science

10. Department of Forest and Wood Science
Methodology
Discs dried and sanded;
Scanned on image analysis programme and year-ring widths measured;
Department of Forest and Wood Science

11. Department of Forest and Wood Science
Methodology
Creation of reconstruction or model of knotty core per tree and compartment;
Radius (mm)
74 mm
72 mm
76 mm
101 mm
Height (m)
Department of Forest and Wood Science

12. Department of Forest and Wood Science
Methodology
Sawing of logs; reconstruction of sub-sample of logs from boards (one log per compartment);
Determination of knotty core size at specific height of log – comparison with model;
Department of Forest and Wood Science

13. Department of Forest and Wood Science
Methodology
Statistical analysis of results;
Application of results: Sawing simulation studies.
Department of Forest and Wood Science

14. Department of Forest and Wood Science
Results
Tree ring measurements, dating of rings relatively easy on the species;
Department of Forest and Wood Science

15. Department of Forest and Wood Science
Results
No difference in mean annual growth results when measuring 2 radii vs. 4 radii at breast height;
Cumulative growth at 6m can be accurately predicted from the independent variables cumulative growth at breast height, site index, and cambial age (R2 = 0.96).
Department of Forest and Wood Science

16. Department of Forest and Wood Science
Results
ANOVA: Far greater variance between compartments than within compartments;
ANOVA: Significant within-tree variance. Bottom log = 49.1% knotty core; Top log = 65.4% knotty core.
Department of Forest and Wood Science

17. Department of Forest and Wood Science
Results
Comparison predicted knotty core size vs. knotty core measured from reconstructed logs (R2 = 0.62):
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18. Department of Forest and Wood Science
Results
Application of knotty core data by forest growers and processors: Cross-cutting decisions and production planning.
Department of Forest and Wood Science

19. Department of Forest and Wood Science
Conclusions
Tree ring measurement and dating is easy and efficient with plantation grown Pinus patula;
Annual growth for the full pruned section can be predicted from growth at breast height and site index;
Two increment cores per tree will be sufficient to predict mean annual growth;
Large variation of knotty cores exist within trees and between compartments;
Influence of nodal swelling, branch stub length, and occlusion scar size need to be investigated (not part of this study);
Knotty core size information per compartment can be used in production planning and bucking decisions.
Department of Forest and Wood Science

20. Department of Forest and Wood Science
Acknowledgements
NMMU (Jos Louw) and Komatiland Forests for assistance in collection of study material.
Department of Forest and Wood Science