Japanese Journal of Forest Environment

Development of studies on forest damage by wind in Japan

Satoshi Saito

Article type: Preface
2010 Volume 52 Issue 2 Pages 47-48
Published: December 25, 2010
Released on J-STAGE: April 03, 2017

DOIhttps://doi.org/10.18922/jjfe.52.2_47

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Effect of the root distributions at inclined slopes on the tree-pulling experiments of Cryptomeria japonica

Nobuyuki Kayashima, Shigeyuki Sasaki

Article type: Article
2010 Volume 52 Issue 2 Pages 49-55
Published: December 25, 2010
Released on J-STAGE: April 03, 2017

DOIhttps://doi.org/10.18922/jjfe.52.2_49

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In order to clarify the effect of the slope angle on the maximum moment of resistance against uprooting, we performed the tree-pulling experiments of Cryptomeria japonica (14 years) at inclined slopes which have four different angles. To examine the relationship between the tree-pulling experiments and root distributions, we also measured root distribution areas, weights and total areas of cross section of roots per 10cm from center of the stump. As the slope was steep, the maximum moment of resistance against uprooting showed to increase in the case of pulling downward compared with upward, and root distribution areas were more extended to upward and sideward than downward. When the slope was steep, weights and total areas of cross section of roots which distributed to upward increased compared with downward. These results showed that the thick roots tended to distribute to upward compared with downward, as the slope was steep. By examining the relationship between the tree-pulling experiments and root distributions, we found that the larger thick roots which distributed to upward, the higher the maximum moment of resistance against uprooting in the case of pulling downward. These results suggest that the partial root distributions at inclined slopes contribute to the results of the tree-pulling experiments, and the maximum moments of resistance against uprooting are different by the slope angle and the direction of pulling.

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Wind profiles and mechanical resistance of uprooted trees in a Japanese cypress (Chamaecyparis obtusa) plantation slightly damaged by Typhoon Melor 0918 at Kamiatago Experimental Forest, Tenryu, Japan : Validity of mechanistic models for wind damage risks

Kenji Kitagawa, Kana Kamimura, Satoshi Saito, Takanori Uchida, Hiromi ...

Article type: Article
2010 Volume 52 Issue 2 Pages 57-66
Published: December 25, 2010
Released on J-STAGE: April 03, 2017

DOIhttps://doi.org/10.18922/jjfe.52.2_57

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In 2009, Typhoon Melor (0918) uprooted trees in a 67-year-old Japanese cypress plantation in the Kamiatago Experimental Forest of Shizuoka University, Tenryu, Japan. Before the typhoon, we had installed anemometers in the forest and conducted tree-pulling trials to construct a model to evaluate the wind damage risk. The unpredictable disturbance event of Typhoon Melor enabled to us to 1) clarify the attributes of trees that show high wind damage risk from both observational and mechanistic aspects, 2) document wind profiles under strong winds that cause uprooting, and 3) discuss the validity of previous models for wind damage risk by comparing them to events that occurred during the typhoon. The proportion of crown size to diameter at breast height was a significant factor for predicting tree damage, but stem taper and tree size were not significant factors. When the wind velocity at 30m height exceeded approx. 7ms^<-1>, there were drastic changes in the vertical wind profile, including an increase in the gradient of wind velocity just above the canopy. For damaged trees, the critical wind speeds calculated using the GALES models were almost three times the maximum mean wind speed observed during the disaster term. The most significant problem in using the models lay in the large discrepancy between the model and actual observations with respect to the pattern of vertical wind profiles in strong wind conditions. These results suggest that it is not valid to use aerodynamic parameters of classical logarithm law in wind damage risk models. However, in terms of tree attributes, the vulnerability of trees predicted by the model was consistent with the observed vulnerability. These results show that the model has some validity in evaluating damage risk based on tree attributes.

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Wind damage simulation in forest and forestry field by CFD technique

Takanori Uchida, Hiromi Mizunaga, Satoshi Saito, Kana Kamimura, Hiroko ...

Article type: Article
2010 Volume 52 Issue 2 Pages 67-77
Published: December 25, 2010
Released on J-STAGE: April 03, 2017

DOIhttps://doi.org/10.18922/jjfe.52.2_67

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In the present study, the generation mechanism of the wind damage was analyzed to examine the possibility of applying CFD (Computational Fluid Dynamics) technique to the field of the forest dynamics and the forest managements. From the simulation by the latest meso-scale climate model NHM, forest damages by Typhoon No.0418 seemed to be caused by southwestern wind in Kokonoe town, Oita Prefecture, Japan. Based on the results, wind condition around the damaged forests was simulated by using a numerical wind synopsis technology RIAM-COMPACT^[○!R]. As a result, it was considered that there were two main causes of wind damage: 1) the local enhancement of wind speed caused by the topographic effect, and 2) the effect of separated airflow from land surface above the damaged area. As shown in the present study, the CFD technique would be an extremely promising approach in the field of the forest and forestry.

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Relationship between stand development and establishment of seedlings in subalpine Abies forest

Shin Ugawa, Toru Hashimoto, Kojiro Iwamoto, Shinji Kaneko, Kenji Fukud ...

Article type: Article
2010 Volume 52 Issue 2 Pages 79-86
Published: December 25, 2010
Released on J-STAGE: April 03, 2017

DOIhttps://doi.org/10.18922/jjfe.52.2_79

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To clarify the relationship between stand development and establishment of seedlings, we examined community structure, relative light intensity (RLI) on forest floor, and establishment of seedlings in four stands of different developmental stage in subalpine Abies forest. We determined the developmental level of each stand based on maximum diameter at breast height and maximum tree height. Tree density was lowest in the most developed stand. Seedling density was highest in the most developed stand, and the RLI was also highest in the stand. The density of 3-10 years old seedling was higher in the most developed stand than younger stands. Therefore, it is suggested that more seedlings can establish in the mature stand with low tree density (i.e., high light intensity) than in younger stands with higher tree density (i.e., lower light intensity). Seedlings were observed with more than 6% of RLI, and the seedling density increased with RLI. Moreover, the RLI decreased with tree density of ≥1.3m in height, and the RLI was 6% in the stand with 6,000 individuals per hectare. Thus, it is thought that Abies seedlings can establish in a mature stand with 6% of RLI when the tree density decreases by 6,000 individuals per hectare with stand development.

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Reconstruction of growth process of forest trees in a young Cryptomeria japonica stand using tree dissection technique

Chiharu Migita, Yukihiro Chiba

Article type: Article
2010 Volume 52 Issue 2 Pages 87-94
Published: December 25, 2010
Released on J-STAGE: April 03, 2017

DOIhttps://doi.org/10.18922/jjfe.52.2_87

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Growth history of trees can be reconstructed using a stem dissection technique that includes an ordinary stem ring analysis and branch knot analysis. The technique for dating life span of branches and estimating past crown dynamics was applied to a 22-year-old Cryptomeria japonica trees. The tree size and the vertical distribution of above ground weights for the harvested trees were evaluated with applying stratified clipping method. Then, the detailed growth history of branches was interpreted through branch knot analysis. Life span of branches was comparatively short due to high stand density: the maximum was 13 years, and the minimum 3 years for each branch; the average branch mortality for each tree was 7 to 8 years. Heights of crown base at every tree age were reconstructed considering the year of branch death and its height above the ground. Using the allometric relationships between tree sizes and dry weights of each organ, tree growth with respect to tree weights, tree size and crown dynamics was reconstructed. Through the analyses conducted in this study, it can be concluded that the stem dissection technique with knot analysis can provide the past record of tree growth including crown expansion/recession, tree weights, and tree size as well.

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On-the spot study meeting of the Japanese society of forest environment "Coastal forests and their environments: from Coastal sand dunes to forests"

Shokichi Wakabayashi

Article type: Record
2010 Volume 52 Issue 2 Pages 95-98
Published: December 25, 2010
Released on J-STAGE: April 03, 2017

DOIhttps://doi.org/10.18922/jjfe.52.2_95

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