Seven-year changes in growth and crown shape of Thujopsis dolabrata var. hondai saplings after release from suppression |
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Authors: | Gaku Hitusma Takayuki Ota Tatsuo Kanazashi Takashi Masaki |
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Institution: | (1) Tohoku Research Center, Forestry and Forest Product Research Institute, 92-25 Nabeyashiki, Shimokuriyagawa, Morioka 020-0123, Japan;(2) Forestry and Forest Products Research Institute, Tsukuba, Japan |
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Abstract: | We investigated changes in sapling growth and morphology of Thujopsis dolabrata var. hondai (hiba) for 7 years after release from suppressed lighting by selection cutting. We examined changes in aboveground biomass,
elongation of stems and lateral branches, and annual diameter increment at the stem base. Vertical distributions of leaves
per branch and per individual were also measured for morphological analysis. Under the suppressed condition before cutting,
the crown consisted of orthotropic lateral branches, elongating up to the top of the stem or farther, and no branch was aborted.
This crown type with large crown depth and concavity of the upper part had a bowl-like appearance. After the selection cutting,
relative light intensity on the saplings increased from 4% to 26%. The increment enhanced aboveground biomass and stem elongation
7 years after the cutting. Diameter growth at the stem base was particularly accelerated 2 years after the cutting. While
crown shape transformation of the saplings was not conspicuous at 7 years after the cutting, some released saplings showed
a superior stem elongation ratio to that of the lateral branches. Thus, the upper part of the crown of these saplings changed
from a bowl-like shape to a convex shape like that of a dome. Our study suggested that suppressed hiba saplings with the unique
bowl-shaped crown enhanced their growth rates rapidly in response to improved light conditions, but required much more than
7 years for the full process of crown transformation for us to identify future trees in this stand.
An erratum to this article is available at. |
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Keywords: | Thujopsis dolabrata var hondai Light acclimation Morphology Crown architecture Apical control |
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