MARK RUDNICKI AND ULDIS SILINS Most forest scientists believe that the allocation of resources to height or diameter growth in trees is controlled by competition for light. However, an alternative explanation relates to how trees allocate resources in response to wind. The uniform stress hypothesis suggests that trees grow in diameter to counteract the increasing bending moment (tendency to bend at the base) from wind energy as trees grow taller. Eventually because of the increased mechanical

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... nstraints from wind, height growth of very tall trees approaches 0 and nearly all resources are put into diameter growth. In this study, we tested the effect of bending stress on the relative height and diameter growth by guying trees to prevent them from bending significantly in wind. Guying was done at 10m height just below the live crown, on groups of 10-15 trees, in three 50 years old, 15m-tall lodgepole pine stands in western Alberta. After 6 years, the trees were cut down, and the height and diameter growth of dominant trees were determined before and after the guying treatment.