A review of strategies for wind damage assessment in Japanese forests

Abstract

Forest management for minimizing wind damage risk requires predicting future wind damage as accurately as possible. However, previous studies carried out in Japan mostly focused on field observation and not on an extensive estimate of damage in various regions. This paper, therefore, aims to understand better approaches to the assessment of wind damage in Japan. First, basic descriptions of wind damage were reviewed including the process and types of tree and stand failures. Several factors relating to wind damage were also described including biological factors and stand characteristics. Second, the current methods of wind damage risk assessment were classified such as (1) observational/empirical, (2) statistical, and (3) mechanistic methods. Of the current methods, the mechanistic methods were acceptable in terms of their prediction of wind damage using the mechanistic behaviour of tree and stand as a result of wind pressure. Third, this paper reviewed previous case studies in Japan and showed that most studies of wind damage focused on particular typhoon events. Their conclusions might be difficult to apply to other settings for the estimation of future wind damage risk with the changes of stand condition (thinning, gap creation, etc.). Therefore, the mechanistic methods would be one of the most powerful approaches to estimate the possibility of future wind damage risk with changes of stand conditions. Further studies are required to develop the methods of wind damage risk assessment in Japan including the mechanical behaviour of tree and stand as a result of wind (typhoon) phenomena.

Keywords:

• Damage factors
• Mechanistic methods
• Risk assessment
• Wind damage

Acknowledgments

This research project is funded by the Academic Research Grant of the Japan Forest Technology Association in 2005. We are grateful to Dr. C.P. Quine, Dr. B. Gardiner, Dr. B. Nicoll, Dr. A. Achim, Dr. J. Suárez, the Forest Research, UK, for helping this research. Our gratitude also extends to Dr. A. Kato, the Toyama Forestry and Forest Products Research Centre, and Professor A. Koizumi, Hokkaido University.

Notes

1 In general, forests frequently face risks of damage caused by abiotic, biotic, and anthropogenic factors. The factors can be categorized as follows: abiotic factors (flood, wind, drought, fire, snow, frost, landslip, volcanism, and glaciations), biotic factors (insects and fungal pathogens and herbivores), and anthropogenic factors (fire, harvesting, road-building, planting, site preparation, drainage, and fertilization) (Quine et al. 1999).

2 Obtaining accurate information for forest inventory is one of critical issues in Japanese forestry. Shiraishi (1998) points out the lack of a monitoring system for updating forest inventory data.

3 Risk assessment is the process of decision-making and/or implementation of actions to reduce windthrow damage (Gardiner and Quine 2000).

4 Such windthrow damages are frequently observed in Germany, Switzerland, Austria, Slovakia, The Czech Republic, Poland, Great Britain, Australia, New Zealand, and Japan (Slodiˇák 1995).

5 According to the field investigation by Papesch et al. (1997) in New Zealand, the maximum resistive bending moment of Pinus radiata is strongly correlated with stem volume, tree height, and diameter at breast height (dbh).

6 The drag coefficient (Cd) is calculated by the total drag force divided by 0.5 ρV²A, where ρ is air density, V fluid (wind) velocity, and A area of crown (Fraser 1962).

7 This is partly because of the genetic variety of wood strength (Isamoto and Takamiya 1992).

8 Buttress formation also helps to reduce stem breakage (Mattheck and Bethge 1990).

9 Tsukamoto et al. (1982) created a model of root architecture and volume using dbh as a main parameter.

10 Development of lateral root size and shape is also strongly influenced by the root movement caused by wind force on the crown (Nicoll and Dunn 2000).

11 Kato (2001) advises that h/d ratio could be used as a snow damage indicator within a stand of uniform cloned trees (i.e., small variability of MOE), due to the large variety of MOE among genetically improved Japanese cedars.

12 Gardiner and Quine (2000) also noted that the trees planted with wider spacing produce large crowns, which are more likely to suffer snow damages.

13 Wind strength is reduced in uneven-aged forests that have canopies with various sizes (Gardiner 1995).

14 According to the models, windthrow damage frequently occurred in high-aged stands. In particular, wind damage increases in the stands just after thinning practice or without thinning over 10 years (Jalkanen and Mattila 2000).

15 Ni Dhubhain et al. (2001) argues that the deterministic method ranks the relative risk of different sites and/or the risk from silvicultural treatments but does not assign a probability to the likelihood of damage.

16 Airflow is often calculated using the extreme value theory because of the difficulty of obtaining long-term wind data (Blennow and Sallnäs 2004). The models are mainly based on mathematical ideas for assessing the wind that blows on hilltops and on slopes behind hilltops (Lekes and Dandul 2000).

17 The main cause of windthrow damage in New Zealand is the occurrence of sub-tropical cyclones combined with topographic conditions (Moore and Quine 2000).

18 A wind speed of 16 m/s caused significant wind damage in the model. As a result, the actual damage tends to be lower than the damage estimated by the HWIND model (Talkkari et al. 2000).

19 Mie prefecture experienced a typhoon in 1991, which took almost the same route as typhoon No. 15 (Isewan typhoon) in 1957 (Nonoda 1995). In addition, forests in Tokachi, Hokkaido suffered typhoon damage three times from 1954 to 2002 (Hokkaido Prefecture 2004). Mason and Quine (1995) mentioned that catastrophic damage resulting from gusts over 40 m/s may be expected to have a return period varying from 1 in 15 years up to 1 in 50 years depending upon the stand location in the forest (i.e., hilltop, valley bottom).

20 Kuboyama et al. (2003) point out that few studies are conducted on the national level.

21 Few case studies about beech (Fagus crenata Blume) have been conducted, while the damage to Japanese cedar has been frequently documented (Hashizume 1994).

22 Savill (1983) thoroughly reviewed the detailed silvicultural procedures (e.g., thinning practices, species selection, etc.) and strategies (e.g., performing the procedures after the storms) in windy climates.

23 One of the strategies for reducing risk may be to avoid heavy or over-constant thinning operations in high-risk stands (Peltola et al. 1999).

24 On the other hand, wide spacing would decrease snow damage, since strong airflow removes snow from branches (Nykänen et al. 1997).

25 Schmoldt (2001) stated that it is difficult to produce a quantitative estimation of windthrow damage because of the limited data sets and the complexity of resource interaction.