Comparative height–crown allometry and mechanical design in 22 tree species of Kuala Belalong rainforest, Brunei, Borneo1

Author

1. Olusegun O. Osunkoya4, 
2. Kharunnisa Omar-Ali, 
3. Norratna Amit, 
4. Juita Dayan, 
5. Dayanawati S. Daud and 
6. Tan K. Sheng

-Author Affiliations

1. Department of Biology and 3Department of Physics, Universiti Brunei Darussalam, Jalan Tungku Link, Bandar Seri Begawan, Brunei Darussalam, Borneo

• Received for publication 15 April 2007.
• Accepted for publication 16 October 2007.
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ABSTRACT

In rainforests, trunk size, strength, crown position, and geometry of a tree affect light interception and the likelihood of mechanical failure. Allometric relationships of tree diameter, wood density, and crown architecture vs. height are described for a diverse range of rainforest trees in Brunei, northern Borneo. The understory species follow a geometric model in their diameter–height relationship (slope, β = 1.08), while the stress–elasticity models prevail (β = 1.27–1.61) for the midcanopy and canopy/emergent species. These relationships changed with ontogeny, especially for the understory species. Within species, the tree stability safety factor (SSF) and relative crown width decreased exponentially with increasing tree height. These trends failed to emerge in across-species comparisons and were reversed at a common (low) height. Across species, the relative crown depth decreased with maximum potential height and was indistinguishable at a common (low) height. Crown architectural traits influence SSF more than structural property of wood density. These findings emphasize the importance of applying a common reference size in comparative studies and suggest that forest trees (especially the understory group) may adapt to low light by having deeper rather than wider crowns due to an efficient distribution and geometry of their foliage.

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