UNDERSTANDING WINDTHROW - SILVICULTURAL IMPLICATIONS

Windthrow is a damaging agent that can be of paramount importance in s ilviculture. Windthrow depends on a number of factors interacting with each other. This paper tries to incorporate windthrow concerns into t he silvicultural decision making process by understanding the windthro w process and its interaction with silviculture. The forces involved i n the windthrow process are reviewed. The effects of natural factors o n these forces are examined and the potential impact of silviculture o n these factors is discussed. Some available hazard rating systems are reviewed, trying to underline their applicability in the Eastern Cana dian context. Climate affects the severity and frequency of storms. Ho wever, wind speed in a particular stand is influenced strongly by loca l topography. Soil and root characteristics determine the sturdiness o f the anchoring system. Many stand-related factors, such as stand heig ht, age, density and stem form, can also exert an influence on the res istance to uprooting. Silviculture can modify the vulnerability to win dthrow by acting on these factors. in stands at risk stripcutting, thi nning or the creation of new margins can cause important losses. The i mpact of stem form also indicates the need for an early control of sta nd density. Among the hazard rating systems available, the British sys tem seems the most complete but would require some adjustments for use in the Eastern Canadian context.