Rubus alceifolius (giant bramble).

R. alceifolius is a robust, aggressive perennial scrambling shrub, spreading by long arching spiny stems, rooting at their tips, as well as by bird-dispersed seeds. It can develop dense impenetrable thickets. It is native to tropical SE Asia but has been introduced to a number of other territories, most notably the Indian Ocean island of La Réunion, where it is one of the eight most threatening plant invaders to become established on the island and occurs not only on sites disturbed by man but also in primary forest with minimal disturbance (Macdonald et al., 1991). It can behave as a liana, climbing into the canopy of forest trees and increasing the risk of wind damage. It occurs also on the islands of Mayotte, Mauritius and Madagascar (Vos, 2004; Kueffer and Lavergne, 2004a,b) and in Queensland, Australia where it is invading pastures, roadsides, creekbanks, sugarcane plantations and the edges of rainforest (Queensland Government, 2012). Holm et al. (1979) record it as a 'principal' weed in Australia, and risk assessment by the Australian method gave a score of 11 (PIER, 2012). Binggeli et al. (1998) classified it as highly invasive in the tropics. In a joint project between USDA and the Weed Science Society of America it was identified among the highest-ranked potential future invasive weeds in USA (Parker et al., 2007; WSSA, 2012).

Assessment of the Risk of Damage to 110 kV Overhead Lines Due to Wind

The article presents an assessment of the risk of damage to 110 kV overhead power lines as a result of the impact of wind of variable speeds on that equipment. A statistical method for the assessment of the reliability of power structures in conditions of variable strength of the structure and at variable exposure values is presented. This method is based on the analysis of the shape and mutual location of the distributions of the probability density of the momentary resistance (strength) of the tested structure and the exposures of variable values occurring in its surroundings. The risk of wind damage to 110 kV lines has been determined on the basis of many years of observations of wind speed and failure rate of the lines. Wind has been shown to be the fault factor or co-factor responsible for damage in one in five failures of such equipment. The final part of the article includes an analysis of the obtained results and their interpretation.

Wind damage over 21 years across different levels of tree removal in natural-origin mixed forests of northwestern British Columbia

In many regions, forestry practices are shifting to partial harvesting approaches that seek to maintain species and structural diversity in managed forests. We monitored windthrow for 21 years following partial cutting treatments with 0%, 30%, and 60% removal in a large, replicated experiment located in mixed-species mature and old-growth forests of fire origin. There was no evidence that wind damage to merchantable trees (≥17.5 cm) varied among the three removal treatments. We found no evidence of a short-term spike in susceptibility to windthrow after partial cutting during the initial years following treatment. Over 21 years, a total basal area of 2.4 m2·ha–1 was damaged, which was 5.9% of the original standing basal area at the start of the experiment. We found clear differences in susceptibility to windthrow among the different tree species. The percentage of original standing trees that were windthrown varied from 0% to 23.7%. Eight of nine species had ≤10% damage over the monitoring period. Foresters should be aware of differences among tree species in risk of wind damage but should not use a general concern about susceptibility to windthrow as a reason to avoid partial cutting systems (that can achieve a diversity of management objectives) in structurally diverse, multispecies forests.

Testing an individual tree wind damage risk model in a naturally regenerated balsam fir stand: potential impact of thinning on the level of risk

Widely distributed in Quebec, balsam fir (Abies balsamea (L.) Mill.) is highly vulnerable to wind damage. Recently, there has been a trend in forest management to increase the use of partial cuttings in naturally regenerating stands, leaving the remnant trees at increased risk of wind damage. In order to limit wind damage after partial cuttings, it is therefore important to find silvicultural practices that minimize the risk of wind damage in these fir stands. Our main objective was to find balsam fir-specific values of parameters to integrate into the wind risk model ForestGALES, in order to simulate the impact of different types of commercial thinning on wind damage risk, and to determine which practice potentially minimizes the risk in a naturally regenerated stand. An anemometer placed at canopy height and strain gauges attached to the trunks of balsam firs allowed us to measure the wind-induced bending moments experienced by a sample of balsam fir trees. This enabled the calculation of the turning moment coefficients specific to each of the trees in order to compare them with the ForestGALES model predictions and to adapt the model for balsam fir stands. The model was tested first with only tree diameter and height as input variables to calculate the turning moment coefficient, then with the addition of a competition index, and finally with the addition of crown dimensions. Wind climate parameters for prediction of the probability of damage were calculated using the Wind Atlas Analysis and Application Program airflow model. The model with the highest accuracy was then used to simulate two types of thinning and determine the impact on wind damage risk for each tree in the stand. According to the model’s predictions, thinning from below has a reduced risk of wind damage compared with thinning from above.

Understanding the interactions between wind and trees: an introduction to the IUFRO 8th Wind and Trees Conference (2017)

This paper discusses the advance in our understanding of the interaction between wind and trees over the last 25 years. It does this by comparing papers in this special issue of Forestry and a companion volume in Agricultural and Forest Meteorology, based on work presented at the 8th IUFRO Wind and Trees Conference in 2017, with papers published in book format after the 1st IUFRO Wind and Trees Conference in 1993. The analysis is divided into sections on ‘airflow and tree mechanics’, ‘forest management and ecology’, ‘tree adaptation and acclimation’ and ‘modelling and statistical techniques’. It is clear that in the last 25 years large advances have been made in our understanding of airflow and turbulence within and above forest canopies and the wind flow and wind loading around and on individual trees. There have also been important developments in the mechanistic and statistical modelling of wind damage risk to forests. Much of the progress has been aided by the enormous advances in measurement systems, computer power and modelling techniques. Furthermore, this knowledge is beginning to influence the approach to temperate and boreal forest management and the development of systems to mitigate the risk of wind damage. At the same time there has been a growing awareness of the ecological impact of wind in many forests around the world, including tropical forests. However, other areas of the effect of wind on trees have progressed much less in the last 25 years. This includes the process of fatiguing in the root-soil system, both during individual storms and over longer periods, and which is known to be a critical factor in the process of windthrow. In addition the exact nature of damage propagation within forests during a storm, and then in subsequent storms, has received relatively little attention although new studies using advanced computational methods are making advances. Of particular relevance, and despite the known critical importance of tree acclimation to the wind, there have been very few studies in the last 25 years on wind acclimation in full-size trees. This is an area of enormous importance in understanding how resistance to the wind varies for different species and between areas with different wind climates. In summary, overall much has been learnt since the 1st Wind and Trees conference but there remain many intriguing and exciting challenges ahead for this multi-disciplinary subject.

Risk zoning of typhoon disasters in Zhejiang Province, China

In this paper, typhoon simply means tropical cyclone. As risk is future probability of hazard events, when estimated future probability is the same as historical probability for a specific period, we can understand risk by learning from past events. Based on precipitation and wind data over the mainland of China during 1980–2014 and disaster and social data at the county level in Zhejiang Province from 2004 to 2012, a study on risk zoning of typhoon disasters (typhoon disasters in this paper refer to affected population or direct economic losses caused by typhoons in Zhejiang Province) is carried out. Firstly, characteristics of typhoon disasters and factors causing typhoon disasters are analyzed. Secondly, an intensity index of factors causing typhoon disasters and a population vulnerability index are developed. Thirdly, combining the two indexes, a comprehensive risk index for typhoon disasters is obtained and used to zone areas of risk. The above analyses show that southeastern Zhejiang is the area most affected by typhoon disasters. The annual probability of the occurrence of typhoon rainstorms >50 mm decreases from the southeast coast to inland areas, with a maximum in the boundary region between Fujian and Zhejiang, which has the highest risk of rainstorms. Southeastern Zhejiang and the boundary region between Zhejiang and Fujian provinces and the Hangzhou Bay area are most frequently affected by extreme typhoon winds and have the highest risk of wind damage. The population of southwestern Zhejiang is the most vulnerable to typhoons as a result of the relatively undeveloped economy, mountainous terrain and the high risk of geological disasters in this region. Vulnerability is lower in the cities due to better disaster prevention and reduction strategies and a more highly educated population. The southeast coastal areas face the highest risk of typhoon disasters, especially in the boundary region between Taizhou and Wenzhou cities. Although the inland mountainous areas are not directly affected by typhoons, they are in the medium-risk category for vulnerability.

Risk Zoning of Typhoon Disasters in Zhejiang Province, China

Abstract: We analyze the characteristics of typhoon disasters and the factors causing them using precipitation and wind data at the county level in Zhejiang Province from 2004 to 2012. Using canonical correlation analysis, we develop an intensity index for the factors causing typhoon disasters and calculate a population vulnerability index for Zhejiang by principal components analysis. Combining these two indexes, a comprehensive risk index for typhoon disasters is obtained and used to zone areas of risk in Zhejiang Province. Southeastern Zhejiang Province is the area most affected by typhoon disasters. The frequency ratio of daily rainfall > 50 mm decreases from the southeast coast to inland areas and is at a maximum in the boundary region between Fujian and Zhejiang, which has the highest risk of rainstorms. Southeastern Zhejiang and the boundary region between Zhejiang and Fujian and the Hangzhou Bay area are most frequently affected by extreme winds and have the highest risk of wind damage. The population of southwestern Zhejiang Province is the most vulnerable to typhoons as a result of the relatively undeveloped economy in this region, the mountainous terrain and the high risk of geological disasters. Vulnerability is lower in the cities and coastal areas due to better disaster prevention and reduction strategies and a more highly educated population. The southeast coastal areas face the highest risk, especially in the boundary region between Taizhou and Ningbo cities. Although the inland mountainous areas are not directly affected by the typhoons, they are in the medium-risk category for vulnerability.