Pankaj K. AGGARWAL IUFRO Division 5 Conference 5.01.01

Pankaj K. AGGARWAL IUFRO Division 5 Conference 5.01.01

Pankaj K. AGGARWAL IUFRO Division 5 Conference 5.01.01 Biological control of wood quality 1 Institute of Wood Science & Technology, Bangalore, India Variation in growth strains in five clones of Eucalyptus tereticornis Pankaj K. Aggarwal and Shakti S. Chauhan Institute of Wood Science & Technology (Indian Council of Forestry Research & Education) Bangalore, India 2

Institute of Wood Science & Technology, Bangalore, India Background India has 2.5% of the geographical area and 1.5% of the world forest area and support 16% population of the world. Gap between demand and supply of timber is widening and therefore shortage of conventional preferred species, high cost, lengthy production period of Conventional species has necessitated the need to utilize man made forests which is available. Conventional technology for Processing is not appropriate for fast grown species as they are inherently characterized by growth stresses due to which they are prone to have processing problems. Also wood is juvenile and liable to cause distortions during sawing and seasoning. 3 Institute of Wood Science & Technology, Bangalore, India What are growth stresses ?

Growth stresses are generated in the cambial layers of woody stems during the cell maturation. Growth stresses are generally resolved in the longitudinal, radial and tangential directions following the natural geometry of the trees. These are common to all species however their magnitudes differ from species to species. Contd Institute of Wood Science & Technology, Bangalore, India In general, these stresses are reported to be less in softwood as compared to hardwood. Most emphasis is paid to longitudinal (axial) growth stresses. They largely determine distortion on sawing. High magnitude of growth stresses results in Brittleheart in standing trees {Low value corewood} End-splitting in logs {Low recovery of sawn timber} Warping, twisting in sawn boards {Excessive

planning wastes and low productivity} Institute of Wood Science & Technology, Bangalore, India Defects due to high growth stresses Growth stresses causes severe sawing problems in plantation timber and thats the reason we need to study this very important parameter. Institute of Wood Science & Technology, Bangalore, India Pattern and distribution The distribution of longitudinal growth stress has been observed to vary progressively from tensile at the periphery to compressive at the centre. The change from tension to compression is considered to occur at about one third to halfway along the radius from the periphery. 7

Institute of Wood Science & Technology, Bangalore, India How do growth stresses originate in trees?? Several theories and hypothesis have been postulated: - Weight of the tree (Martley,1928) - Longitudinal cell shortening (Jacobs,1938) - Lignin swelling (Boyd,1985) - Cellulose tension (Bamber, 1979,1987) - Combination of LS and CT (Okuyama, 1993, 2000) 8 Institute of Wood Science & Technology, Bangalore, India Why this study ?

Eucalyptus - planted extensively mainly for pulp and paper and fuel wood Utilization of this species is limited due to growth stresses Improvement in both breeding and processing of the plantation grown species is gaining importance. With the clonal forestry gaining significant thrust for quality production, it is desirable to study the variation in growth stresses in different clones.

Selection of appropriate clones provide an opportunity to grow trees with pre-defined wood characteristics for future production. Institute of Wood Science & Technology, Bangalore, India 9 Objectives Utilization of clonal material of eucalypts and propagation of low stresses clones through evaluation of : Variation in growth strains in clones raised by Indian Tobacco company (ITC). Variation of strains with diameter. Institute of Wood Science & Technology, Bangalore, India 10

Materials 6 logs of each of five clones obtained from ITC Bhadrachalam in Andhra Pradesh (a southern state in India.) Diameter of the logs- 9 cm to 17 cm. Age at the time of measurements- 8 years 11 Institute of Wood Science & Technology, Bangalore, India Measuring growth stresses It is not possible to measure growth stresses directly. Growth strains can be measured with greater ease by relieving the stresses. The magnitude of released growth strains can be considered an indicator of growth stresses, as stresses are proportional to strains within the elastic region.

Contd Institute of Wood Science & Technology, Bangalore, India Measuring growth stresses . Growth stresses are evaluated by growth strain and modulus of elasticity. For measurement of growth strain there are several techniques: (a) Plank stripping method (b) Nicholsons Method (c)The French method (d) The strain gauge method We have measured growth strain using strain gauge method. Contd. 13

Institute of Wood Science & Technology, Bangalore, India Measuring growth stresses Longitudinal strains were measured in logs using strain gauges. Strain gauges were glued to the wood surface. Wood fibres were cut above and below the strain gauge to release the growth stresses. Strains were recorded. Strain gauge Eucalypt log Contd

Institute of Wood Science & Technology, Bangalore, India Measuring growth stresses Hole diameter (30 mm) Hole depth (20 mm) Distance between hole edge and strain gauge (10 mm) Contd 15 Institute of Wood Science & Technology, Bangalore, India Measuring growth stresses Strain measuring indicator 16

Institute of Wood Science & Technology, Bangalore, India Advantages of strain gauge method It is less destructive method as compared to other available methods. It is more suitable for measuring longitudinal strain in a very thin layer of wood. Instantaneous recording of the strain value. Compact and suitable for repeated measurement. Measurement can be made at several points simultaneously

However, it is expensive. 17 Institute of Wood Science & Technology, Bangalore, India Variability between different clones Growth strain (x10-6) 1200 1000 800 600 400 877 602 200

466 491 C D 640 0 A B E Clone Number

18 Institute of Wood Science & Technology, Bangalore, India Analysis Source of Variation With-in clone SS df MSS Fcal p Fcrit

210020 5 42004.01 0.86 0.52 2.71 Between clones 641178.6 4

160294.7 3.30 0.03 2.87 Error 971302.6 20 48565.13 Total 1822501

29 ANOVA indicates a significant difference in growth strains between different clones. 19 Institute of Wood Science & Technology, Bangalore, India Difference in strain on two sides Strain on side B (x 10 -6) 1200 y = 0.76x + 17.94 R2 = 0.66 1000

800 600 400 200 0 0 200 400 600 800 1000 1200

1400 Strain on side A (x 10-6) Significant association between strain measured on one side with the strain on opposite side in logs 20 Institute of Wood Science & Technology, Bangalore, India Relationship between log diameter and growth strains -6 Growth strain (x10 ) 1400 y = 76.36x - 244.42 2

R = 0.24 1200 1000 800 600 400 200 0 7 9 11 13 15 Diameter (cm)

17 19 No strong association between log diameter and growth strains 21 Institute of Wood Science & Technology, Bangalore, India Conclusions Growth stresses is one of the most important wood quality criteria The study revealed a significant variation in growth strains between different clones providing an opportunity to select low stress clone for sawn timber production. There was a significant association between strain measured on one side with the strain on opposite side in logs. These suggests that a single measurement of strain on a log could indicate magnitude of stresses for screening purpose.

Tree growth as represented by the log diameter does not appear to have any significant association with growth strains. 22 Institute of Wood Science & Technology, Bangalore, India Acknowledgement: -IUFRO for SAP -FAO for partial funding -ICFRE for supporting my work -MoEF, Govt. of India -Authorities at my institute -Dr Andrew wong -Dr Susan Siau 23 THANK YOU

24 Institute of Wood Science & Technology, Bangalore, India

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