Effects of bending stress on taper and growth of stems of youngEucalyptus regnans trees |
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Authors: | G H R Osler P W West G M Downes |
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Institution: | (1) Cooperative Research Centre for Temperate Hardwood Forestry, Locked Bag 2, 7005 Sandy Bay, Tasmania, Australia;(2) CSIRO Division of Forestry, Locked Bag 2, 7005 Sandy Bay, Tasmania, Australia;(3) Cooperative Research Centre for Hardwood Fibre and Paper Science and CSIRO Division of Forest Products, Rosebank MDC, Private Bag 10, 3169 Clayton, Victoria, Australia;(4) Present address: Department of Biological Sciences, Macquarie University, 2109 New South Wales, Australia;(5) Present address: CRC for Tropical Savannas, Northern Territory University, 0909 Darwin, Northern Territory, Australia |
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Abstract: | A glasshouse experiment investigated the effect of bending stress on stem radial and height growth and stem taper ofEucalyptus regnans seedlings. Eighteen-week-old, potted seedlings were bent continuously for 8 weeks with a static bending stress. The bending treatment was then removed and the seedlings grown for another 12 weeks. Other seedlings were stayed vertically throughout the experiment whilst control seedlings were neither bent nor stayed. Seedlings were rotated every 2 days to prevent reaction wood developing asymmetrically in the stems of bent trees. Bent trees had higher radial growth rates, developed more tapered stems and had higher safety factors (the ratio of stem radius to the minimum radius required to prevent the tree toppling over) than unbent seedlings. They produced a band of tension wood in their stems and ceased height growth whilst bent. When bending ceased, they resumed normal radial and height growth. Unbent trees developed more cylindrical stems. There were no differences in growth behaviour between stayed and control trees. Bent and unbent trees all developed a butt swell, the taper of which was not affected by treatment. It was concluded that bending stress has substantial effects on both the size and taper of tree stems. However, the development of butt swell is independent of the bending stress applied. The results were considered in relation to biomechanical theories of tree stem development. |
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Keywords: | Bending stress Stem shape Radial growth rate Eucalyptus regnans |
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