Mechanical Structure and Development of Climbers

Lianas are currently understood to have a range of important ecological functions in forest dynamics, of which a number are mechanical (Figure 2.1). Mature lianas climbing to the forest canopy can literally tie neighboring trees together (Figures 2.1c and 2.1d); they can weigh down and distort tree growth or even cause main branches or entire trees to fall. Young stages of liana growth can be particularly well adapted to spanning long distances even though they are composed of only narrow stems (Figures 2.1a and 2.1b), bridging host supports and exploring and filling open and disturbed areas, often to the detriment of self-supporting species. These specialized strategies are made possible in many climbing species by highly adapted mechanical properties of the stem. A number of recent studies have explored the developmental, ecological, and evolutionary significance of the transition from relatively stiff young shoots to older more flexible stems [5-10]. This developmental trend differs from most self-supporting plants, which are normally composed of relatively compliant tissues when young and relatively stiff tissues when old. Many vine and liana stems show extreme changes in mechanical properties during development from young to adult plants (Figure 2.1), and these changes have a significant effect on how they exploit the environment. Climbers are particularly active in early successional and secondary forests as well as forest margins and disturbances within forests, including tree falls and tree fall gaps.

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