Title

The role of Douglas-fir stem sapwood andheartwood in the mechanical and physiological support of crowns and development of stem form

Document Type

Article

Journal/Book Title/Conference

Can. J. For. Res.

Volume

11

Publication Date

1-1-1981

First Page

459

Last Page

464

Abstract

The mechanical and physiological support of a tree's crown is the principal function of its bole. A simple model for Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) of different crown classes explains much of the observed differences in stem form development. Sapwood cross-sectional area at any height on the bole of the tree was found to be related linearly to the amount of foliage above that point; however, in large trees the sapwood area needed to supply transpiring foliage with water is insufficient to provide mechanical support. The combination of sapwood and heartwood was found to provide the stem form that would be expected to ensure uniform resistance to bending by the wind.

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