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Thinning alters crown dynamics and biomass increment within aboveground tissues in young stands of Chamaecyparis obtusa |
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| Authors: | Qingmin Han Daisuke Kabeya Satoshi Saito Masatake G Araki Tatsuro Kawasaki Chiharu Migita Yukihiro Chiba |
| Institution: | 1. Department of Plant Ecology, Forestry and Forest Products Research Institute, Matsunosato 1, Tsukuba, Ibaraki, 305-8687, Japan 2. Hokkaido Research Center, Forestry and Forest Products Research Institute, Hitsujigaoka 7, Toyohira, Sapporo, Hokkaido, 062-8561, Japan 3. Kyushu Research Center, Forestry and Forest Products Research Institute, Kurokami 4-11-16, Kumamoto, 860-0862, Japan 4. Research Planning and Coordination Department, Forestry and Forest Products Research Institute, Matsunosato 1, Tsukuba, Ibaraki, 305-8687, Japan |
| Abstract: | The stand density of a forest affects the vertical distribution of foliage. Understanding the dynamics of this response is important for the study of crown structure and function, carbon-budget estimation, and forest management. We investigated the effect of tree density on the vertical distribution of foliage, branch, and stem growth, and ratio of biomass increment in aboveground tissues; by monitoring all first-order branches of five trees each from thinned and unthinned control stands of 10-year-old Chamaecyparis obtusa for four consecutive years. In the control stand, the foliage crown shifted upward with height growth but the foliage quantity of the whole crown did not increase. In addition, the vertical distribution of leaf mass shifted from lower-crown skewed to upper-crown skewed. In the thinned stand in contrast, the foliage quantity of individual crowns increased two-fold within 4 years, while the vertical distribution of leaf mass remained lower-crown skewed. The two stands had similar production rates, numbers of first-order branches per unit of tree height, and total lengths of first-order branches. However, the mortality rate of first-order branches and self-pruning within a first-order branch were significantly higher in the control stand than in the thinned stand, which resulted in a higher ratio of biomass increment in branch. Thinning induced a higher ratio of biomass increment in foliage and lower in branch. The increased foliage quantity and variation in ratio of biomass increment after thinning stimulated stem growth of residual trees. These results provide information that will be useful when considering thinning regimes and stand management. |
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