Environmental influence on wood quality. I. Distribution and amount of compression wood within the stems of young sugi and hinoki trees grown in a heavy snowfall district.
The distribution of compression wood (CW) was studied in sugi (Cryptomeria japonica) and hinoki (Chamaecyparis obtusa). Two varieties of sugi were used: okinoyama-sugi, which grows in western Japan and is adapted to snow, and boka-sugi, which grows in central Japan. Boka-sugi trees showed large stem curvature of both basal sweep and stem sweep types due to snow creep on the slopes, and also had a high content of CW on both downhill and uphill sides of the stem. Okinoyama-sugi had only slight stem curvature and less CW than boka-sugi. Hinoki trees showed different amounts of stem curvature on gentle vs. steep slopes, but little difference in CW content. This is ascribed to an intensive training method called yuki-okoshi, used on steep slopes, which reduces curvature and excessive CW formation. In 4- to 15-yr-old stems, there was a positive correlation between amount of CW formed each year and annual rainfall (r = 0.45-0.85).