Ecosystem responses to variable-density thinning for forest restoration in Mill CreekAuthor(s): Lathrop P. Leonard; John-Pascal Berrill; Christa M. Dagley
Source: Gen. Tech. Rep. PSW-GTR-258. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 287-290
Publication Series: General Technical Report (GTR)
Station: Pacific Southwest Research Station
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Variable-density thinning (VDT) has promise as a forest restoration tool that accelerates development of old-growth redwood (Sequoia sempervirens (D.Don) Endl.) forest characteristics (O’Hara et al. 2010) but can lead to bear damage in north coastal California (Hosack and Fulgham 1998, Perry et al. 2016). Three novel VDT prescriptions (O’Hara et al. 2012) were tested across an extensive area at the Mill Creek addition of Del Norte Coast Redwoods State Park, near Crescent City, in Del Norte County, California. This area is primarily composed of young, crowded forests dominated by Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) regenerating after a history of industrial forest management. These forests were once dominated by large, widely-spaced redwood and Douglas-fir, and are located in a watershed that plays an important role in protecting old-growth forest located downstream in Jedediah Smith Redwoods State Park. The even-aged stands prioritized for VDT had been regenerated between 1982 and 1992, and prior to treatment had around 1300 stems ha-1 averaging 15 cm diameter at breast height (DBH; 1.37 m) of which 2/3 were Douglas-fir.
Each stand was assigned one of four experimental prescriptions replicated five times throughout the ownership and monitored in large sample plots. Three plots were established in each stand soon after treatment (within 1 year of the treatment date). All plots were then re-measured 4 years after establishment. We summarized tree- and stand data from the 60 monitoring plots in 20 stands receiving one of four treatments: low-density thin to 6.1 m spacing (LDT), high-density thin to 4.9 m spacing (HDT), localized release (LR), and no-thin control (C). Specifically, we calculated averages for each monitoring plot, and compared these averages among the four treatments. Our objectives were to compare the effectiveness of VDT treatments at promoting redwood dominance, redwood tree growth, and stand structural complexity. We also compared incidences of bear damage and depth of slash following each thinning treatment and over the same time period in unthinned control stands.
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CitationLeonard, Lathrop P.; Berrill, John-Pascal; Dagley, Christa M. 2017. Ecosystem responses to variable-density thinning for forest restoration in Mill Creek. In: Standiford, Richard B.; Valachovic, Yana, tech cords. Coast redwood science symposium—2016: Past successes and future direction. Proceedings of a workshop. Gen. Tech. Rep. PSW-GTR-258. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 287-290.
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