Growth was assessed for Douglasfir reproduction which had established naturally beneath three intensities of overstory thinning in a 65-year-old stand of Douglas-fir on the east side of the Oregon Coast Range. The age of advanced reproduction ranged from 4 to 15 years. Understory environments were described in terms of sunlight, plant moisture stress, evaporative demand, air and soil temperatures, and vegetative cover. Daily sunlight reaching the reproduction, averaging 5 to 12 percent of full sun, best separated the three understory environments and correlated directly with the intensity of overstory thinning. Tree height and sunlight positively interacted with growth increment. Mean growth increased linearly with thinning intensity, and current growth highly correlated with growth and tree height of previous years.
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