THE ADAPTIVE SIGNIFICANCE OF TRUNK INCLINATION - A FURTHER THOUGHT

A recent paper in this journal has criticized our previous study, in w hich we identified an adaptive significance of trunk inclination on sl opes. Our main argument was that a tree on a slope may gain some benef it by leaning, which provides the tree with shorter access to the cano py light, and thus a better chance for survival, and that if this bene fit outweighs the cost involved in leaning, trunk inclination will be favoured by selection. Although the criticisms are based on some misun derstandings, the situations considered in the critique, which are dif ferent from ours, have inspired us into an extension of our previous s tudy. In the course of a reply to the criticisms, we present a further thought on the adaptive significance of trunk inclination in a broade r scope. Specifically, we show that our model, with its modified formu lation of the benefit component of tree leaning, may evaluate the fitn ess of a tree with its trunk inclined. It can also be used to examine the conditions for tree leaning, and make predictions on the optimal t ree leaning in any situations, including canopy gaps and permanent ope nings, which the critique is mainly concerned with.