Lean in red alder (Alnusrubra): growth stress, tension wood, and righting response

Abstract

Natural stands and a 3-year-old plantation of red alder (Alnusrubra Bong.) trees were used to study the incidence of leaning stems, the level of growth stresses and tension wood formation, and the ability of the stems to right themselves to vertical. Overall, 10% of the 512 trees in 10 natural stands leaned >22°. The largest diameter trees on the steepest slopes leaned most. Most (61%) of the trees curved upward, showing a righting response. For samples without tension wood, growth stress levels on the upper side of leaning stems, but not on the lateral or lower sides, were positively correlated with lean angles above 6°. These leaning stems had a significant righting response without tension wood. Tension wood formation was variable at leans from 9° to 26° both within and among trees, but was correlated with eccentric growth rings. We measured stem recovery in the year-old stem of 3-year-old trees bent to angles of 0–37.5°. During the 5-month experiment all stems righted to near vertical. Tension wood formed on the upper side in stems bent >6°, but reversed to the lower side before reaching vertical in 22 of 30 trees.

The Gravitropic Response of Poplar Trunks: Key Roles of Prestressed Wood Regulation and the Relative Kinetics of Cambial Growth versus Wood Maturation

“…Studies of gravitropism in aerial organs with secondary radial growth such as tree trunks or branches are less frequent (e.g. Sinnott, 1952;Archer and Wilson, 1973;Yoshisawa and Okamoto, 1986;Wilson and Gartner, 1996). Moreover, quantification and mechanical analyses of the tropic movement of lignified axes over time have been little considered (except for a few studies on conifers; Archer andWilson 1973, 1982;Fournier et al, 1994).…”

Modelling the biomechanical behaviour of growing trees at the forest stand scale. Part I: Development of an Incremental Transfer Matrix Method and application to simplified tree structures

“…Stimuli of reaction wood formation are not wellknown. However, the secondary reorientation criterion can be given as a function of the stem leaning angle [1,37,42,44,46]. It can also be dependent on other variables, such as the stress (or strain) field for instance [11].…”

“…Moreover, as mentioned above, intermediate values of could be used in order to modulate the straightening up intensity. This parameter could be particularly given as a function of the leaning angle allowing the correlation between negative-gravitropism intensity and stem inclination to be taken into account [42,44,46].…”

Effet de l?intensit� d?un stimulus gravitationnel induit artificiellement sur la croissance et la formation du bois de tension dans de jeunes pousses de peuplier (Populus euramericana cv ?Ghoy?)

“…Bien que l'excentricité et le bois de tension soient généralement associés dans un arbre, la question s'est posée de savoir si ces deux phénomènes étaient pour autant liés ? En effet, des observations ont montré que du bois de tension pouvait se former également sur des axes apparemment verticaux ou à l'opposé de l'excentricité [25,38,47,53,54]. Confrontés à la difficulté d'interpréter a posteriori sur des arbres adultes, la formation du bois de tension et les modifications de la croissance, des expérimentateurs ont induit artificiellement ces phénomènes en appliquant un stimulus gravitationnel obtenu par l'inclinaison de jeunes pousses.…”

“…Il résulte que, généralement, il existe une relation entre l'inclinaison des axes et d'une part, le pourcentage de bois de tension et d'autre part, l'excentricité de la moelle [28,35,53]. Cependant, d'autres auteurs mentionnent l'absence de relation [1,19,43,54]. Pour Fisher et Stevenson [21], le redressement des axes est lié à la distribution des fibres gélatineuses (fibres G caractéristiques du bois de tension) dans le bois.…”