Stem eccentricity in coastal western hemlock

Abstract

Stem eccentricity in second-growth western hemlock (Tsugaheterophylla (Raf.) Sarg.) from southern coastal British Columbia appears to be the rule rather than the exception. Although the difference was small, the average eccentricity ratios (ratios of minimum diameter inside bark (DIB) to maximum DIB) for two Lower Mainland sites were significantly larger than those of two Vancouver Island sites. The average eccentricity ratio of all 87 trees studied was 0.929, with a standard deviation of 0.0231. The angular rotation of the major axis of the stem cross section varied greatly, and was positively related to the average stem eccentricity ratio within 5-m log lengths for each stem. Average eccentricity of the whole stem was relatively independent of diameter at breast height (DBH), age, stem height, and eccentricity at breast height. It does not appear that a practical field technique could be devised for the rapid estimation of average stem eccentricity in western hemlock.