The mechanical stability of the world’s tallest broadleaf trees

Abstract

13The factors that limit the maximum height of trees, whether ecophysiological or mechanical, are the 14 subject of longstanding debate. Here we examine the role of mechanical stability in limiting tree 15 height and focus on trees from the tallest tropical forests on Earth, in Sabah, Malaysian Borneo, 16including the recently discovered tallest tropical tree, a 100.8 m Shorea faguetiana. We use 17 terrestrial laser scans, in situ strain gauge data and finite-element simulations to map the 18 architecture of tall broadleaf trees and monitor their response to wind loading. We demonstrate 19 that a tree's risk of breaking due to gravity or self-weight decreases with tree height and is much 20 more strongly affected by tree architecture than by material properties. In contrast, wind damage 21 risk increases with tree height despite the larger diameters of tall trees, resulting in a U-shaped 22 curve of mechanical risk with tree height. The relative rarity of extreme wind speeds in north Borneo 23 may be the reason it is home to the tallest trees in the tropics. 24

Height growth and biomass partitioning during secondary succession differ among forest light strata and successional guilds in a tropical rainforest

“…Second, for sub-canopy trees there is a premium on height growth, as a small increase in tree height results in the largest increase in light availability because the HIP indicates the steepest part of the light gradient (Matsuo et al 2021). Third, canopy trees may have diminishing returns on height growth and thus invest more in diameter growth to improve stability against wind (Sterck and Bongers 1998) and water supply against drought stress (Jackson et al 2021), or in horizontal crown growth to increase light interception (King 1996).…”

The World's Tallest Tropical Tree in Three Dimensions

“…Interestingly, the tall Eucalyptus regnans appears to have a very different, superficially somewhat gymnosperm-like architecture, with a wide trunk diameter and short branches extending throughout much of its length. An analysis based on the three dimensional model of Menara (Jackson et al, 2019b) suggests that this tree is a long way from buckling under its own weight (it would need to attain approximately 255 m in height to hit that threshold), but is vulnerable to breakage under moderate wind speeds, and therefore may be close to a wind-related maximum height constraint. The methods employed in this mechanical analysis are excluded here for readability, but are explained in detail in (Jackson et al, 2019a).…”