Whiskey springs long-term coast redwood density management; final growth, sprout, and yield results
This article is part of a larger document. View the larger document here.Abstract
Multi-decadal studies of commercial and precommercial thinning in redwood stands are rare and consequently of value. The Whiskey Springs study at Jackson Demonstration State Forest has a data set spanning 35 years. In addition to growth and yield response to commercial thinning, the results provide important information for evaluating regeneration and alternative silviculture treatments.
In 1970, the original treatment thinned a 40 year-old redwood forest from below to densities representing 25, 50, and 75 percent of the initial basal area (approximately 400 ft2/ac). Three 0.2-ac plot replicates within each of the four density levels were assigned in a randomized design. In the 35 years after thinning, the basal area of the 25, 50, 75 and 100 (control) percent retention areas increased by 168, 232, 226 and 210 ft2/ac of basal area respectively. There was some indication that mean annual increment (ft3/ac) had culminated at age 70 years for some treatments.
Redwood sprouts and other conifer seedlings were abundant in the 25 and 50 percent retention areas. Precommercial thinning subplots were established within these two treatments in 1986, reducing the understory to 200, 300, and 400 sprouts/ac. The understory diameters ranged from 2 to 6 inches at DBH for the 25 percent retention 35 years after the commercial thinning.