© 1986 Heron Publishing—Victoria, Canada
Transpiration of a 31-year-old Chamaecyparis obtusa Endl. stand before and after thinning
Yasushi Morikawa (1), Shigeaki Hattori (2) and Yoshiyuki Kiyono (1)
1. Forestry and Forest Products Research Institute, P.O. Box 16, Tsukuba Norin Kenkyu Danchi-nai, Ibaraki 305, Japan / 2. Kansai Branch, Forestry and Forest Products Research Institute, Fushimi, Kyoto 612, Japan /
Summary
Daily transpiration before and after thinning was measured on six individual trees in a 31-year-old Chamaecyparis obtusa Endl. stand by the heat pulse method. After thinning, daily transpiration of a tree at a given level of solar radiation increased,
and the difference between before and after thinning increased with solar radiation. The increase after thinning was related
to a high rate of crown transpiration caused by greater canopy exposure and, subsequently, to the increase in foliage biomass
per tree. Stand transpiration was calculated on the basis of two parameters, daily solar radiation and daily maximum vapor
saturation deficit of the air. During the growing season (April to September), transpiration of a tree increased following
thinning whereas transpiration of the stand decreased 21% after thinning. This decrease was associated with a 24% decrease
in leaf mass of the stand following thinning.
