Abstract
Leaf biomass and stem biomass production were measured for 10 years in hinoki cypress plantations that were exposed to different thinning intensities in three areas at different altitudes in Kochi Prefecture. Leaf biomass was estimated using a simple method based on the pipe model theory. The increase rate of leaf biomass and percentage of
stem removal were positively, linearly related and the increase rate was lower in the higher altitude area. There was
a linear log/log relationship between leaf biomass and stem biomass production, the regression lines for which had slopes of 1.066 in the high-altitude area and 0.638–0.661 in the two lower altitude areas. The foliage efficiency, i.e., stem biomass production per unit of leaf biomass, was predicted from these relationships. Foliage efficiency increased
with an increasing percentage of stem biomass removal in the lower altitude areas but not in the high-altitude area.
The increase in stem biomass production in thinned plots could be divided into the effects of changes in leaf biomass
and foliage efficiency. Leaf biomass had a larger effect in the moderately thinned plots with only small difference between areas, whereas foliage efficiency varied between areas in strongly thinned plots. These findings suggest that
foliage efficiency is a useful index for comparing thinning effects between areas.
