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Extensive Hail Damage in Northern Manitoba

1966; Canadian Institute of Forestry; Volume: 42; Issue: 2 Linguagem: Inglês

10.5558/tfc42198-2

1499-9315

J. G. Laut, K. Elliott,

Aeolian processes and effects

Hail commonly causes damage to forest stands and often predisposes trees to further serious damage by fungi and insects.As noted by Riley (1953), hail damage usually affects relatively small areas.Seven such areas ranging from about 10 to 40 square miles and an unusually large one of about 600 square miles were observed during a routine aerial survey in northern Manitoba in 1965.These areas were within a broad band extending from Landing Lake (near Thicket Portage on the northern line of the Canadian National Railway) southeasterly to Red Sucker Lake near the Ontario boundary.The forest cover in this part of Manitoba is predominantly jack pine with some trembling aspen, white birch, white spruce, and balsam fir along the lakeshores and riverbanks, and with black spruce and tamarack in low-lying areas.In each area, the damage was detectable from the air by the reddish-orange colour of dead jack pine foliage which was distinguishable from other types of foliage damage, such as insect defoliation, by its brightness and the dense appearance of individual tree crowns.Within the largest area, which extended from Red Sucker Lake northward around the east end of Sharpe Lake to Edn~und Lake, the damage was patchy and was most severe in the central portion where, from the air, most of the jack pine appeared to be dead.Ground examination at Landing Lake revealed that although only jack pine damage was visible from the air, all tree species were damaged.Dead spruce branches were not visible from the air because their needles had dropped to the ground and the dead branches or crowns of deciduous species were not discernible against the undergrowth.Damage consisted principally of dead twigs and branches and occasional dead tops with some dead trees present in the damaged stands.Hailstone lesions, similar to those described by Riley (1953) and Linzon (1962) were numerous on branches and main stems mainly on the northwest side of the trees.Many of the lesions on all tree species were on the undersides of the branches indicating that extremely strong winds had accompanied the hail.Jack pine lesions showed little evidence of having healed over.The condition of the lesions and the appearance of the dead jack pine foliage remaining on the trees indicated that the damage had been inflicted in 1964.There are no official weather stations in this part of the Province, but the Conservation Officer of the Manitoba Department of Mines and Natural Resources at Island Lake, V. Guttman, recorded a hailstorm with winds up to 80 m.p.h. on July 23, 1964, and the manager of God's Lake Lodge at God's Lake had noted that a party of fishermen were almost swamped in their boat during a severe hailstorm in the second week of September 1964.Island Lake is about 35 miles south, and God's Lake is about 25 miles northwest, of the largest damage area.Although the colour of the foliage suggested that all the damage had occurred at the same time, it is probable that both storms and perhaps several others had contributed to it.REFERENCES