sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

SDU Faculty of Forestry Journal
Serial: A, Number: Special Issue, Year: 2009, ISSN: 1302-7085, Page: 238-240
HAIL DAMAGE OF FOREST TREES IN WESTERN CANADA
ABSTRACT
Yasuyuki HIRATSUKA 1*
1 Northern Forestry Centre, Canadian Forest Service
Edmonton, Alberta CANADA
* yahirats@nrcan.gc.ca
Hail and hail storms damage agricultural and horticultural crops, as well as vehicles,
houses and other buildings; these weather events also cause various degrees of damages to
forest trees. Western Canada, with its diverse topography and varied weather systems, is
known to have frequent hail storms. In the Canadian Rockies in the fall of 2008, a severe
discoloration of foliage and many dead branches were observed over several hectares of a
subalpine fir (Abies laciocarpa (Hook.)Nutt.) stand. After examining the symptoms and
topographical features of the affected area, it was concluded that the damage was caused by
a hail storm. Hail damage as well as other weather-related damage to forest trees, such as
frost damage and drought damage, are often predisposing factors of branch and foliage
symptoms associated with pathogenic fungi belonging to such genera as Nectria,
Cytospora, and Sphaeropsis, and this weather-related damage should be considered when
diagnosing forest tree health problems.
Keywords: hail damage, western Canada, non-biotic tree diseases, predisposition
1. INTRODUCTION
Hail or hail storms usually occur at the front of storm systems from spring to
fall but rarely during cold winter weather. Hail is formed when updrafts in
thunderclouds carry rain drops upward into extremely cold areas of the cloud and
form ice particles; updrafts carry the ice particles to the cold region of the storm
clouds, where the size of the ice particles increases. When the ice particles become
too heavy to be supported by the updraft, they fall to the ground at speeds of up to
100 km/h. Hail storms can cause damage to crops, houses, and vehicles as well as
injuries to people and animals. Hail damages to forest trees have often been
reported (Benjamin, 1957; Grayburn, 1957; Hiratsuka and Zalasky, 1993; Laut and
Elliott, 1966; Nelson, 2009; Riley, 1953).
Hail storms occur more frequently along mountain ranges because winds
(moving in a horizontal direction) react to the change in topography, shifting
upwards within thunderstorms and creating favorable conditions for the creation of
hail and hail storms. Hail storms are known to occur throughout many parts of the
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