Snow damage to young Western hemlock and Douglas-fir Public Deposited
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Data collected from permanent sample plots at medium and high elevations in Oregon's coastal forest clearly indicate that snow damage adversely influences stand development. Sapling stands of western hemlock and Douglas-fir were subjected to severe snow damage above 1,000 feet in the early parts of 1965 and 1966 and above 2,500 feet in the winter of 1968-69. These data were collected from thirty-two 1/10-acre plots in four locations in western Oregon. The plots, thinned and unthinned, were in site-quality classes III and IV. Damage varied among the locations and also among the plots in each location. The percentage of damaged trees ranged from 0 to 77.9. Damage was considered severe when 30 percent of the trees were injured in stands spaced about 4 by 4 feet, equivalent to about 2,700 trees per acre before the snowfall. The study showed that: Trees growing openly at seedling and early sapling stages offered more resistance to snow injuries than trees in densely stocked stands. Sapling stands 21 years old, thinned 2 years before the snowfall, had more damage than an adjacent unthinned stand. Extremely heavy snowfall caused severe damage in a dense, unthinned stand, hut damage in an adjacent stand thinned 6 years before the snowfall was very light. The percentage of damaged trees in sapling stands decreased with increase of tree diameter. In mixed stands of saplings, Douglas-fir trees were more susceptible to snow injuries than western hemlock. Early, heavy thinning is recommended to avoid damage from snow.
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