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Effects on understory biomass and forage 8-10 years after precommercial thinning of Sitka spruce - western hemlock stands in southeast AlaskaAuthor(s): Justin S. Crotteau; Annelise Z. Rue-Johns; Jeffrey C. Barnard
Source: Canadian Journal of Forest Research. 32(4): 215-225.
Publication Series: Scientific Journal (JRNL)
Station: Pacific Northwest Research Station
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DescriptionIn southeast Alaska, United States, multiple-use forest management objectives include both timber production and wildlife habitat. Following stand-replacing disturbances such as clear-cutting, Sitka spruce (Picea sitchensis (Bong.) Carrière) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) naturally regenerate and competitively dominate resources, excluding understory biomass and biodiversity. Thinning may mitigate the effects of canopy closure and permit understory development, but evidence of the effect on understories 8–10 years after thinning is lacking. We report results 4–5 and 8–10 years after thinning experiments on the Tongass National Forest to demonstrate the effects of precommercial thinning (thinned versus control), stand age (15–25, 25–35, and 35–50 years), and weather on understory dynamics and Sitka black-tailed deer (Odocoileus hemionus sitkensis Merriam, 1898) forage availability. Stand density negatively affected understory biomass, whereas temperature and precipitation positively interacted to increase biomass. Thinning had an enduring effect on understories, with biomass at least twice as great in thinned versus unthinned stands through year 10. We identified compositional differences from thinning as stand age class increased. Deer forage responded similarly to biomass, but thinning-induced differences faded with increased winter snowfall scenarios, especially in older stands. This study aids the understanding of stand overstory and understory development following silvicultural treatments in the coastal temperate rain forest of Alaska and suggests management implications and applications for balancing objectives throughout the forest type.
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CitationCrotteau, Justin S.; Rue-Johns, Annelise Z.; Barnard, Jeffrey C. 2019. Effects on understory biomass and forage 8-10 years after precommercial thinning of Sitka spruce - western hemlock stands in southeast Alaska. Canadian Journal of Forest Research. 32(4): 215-225.
KeywordsTongass-Wide Young-Growth Studies, Sitka spruce (Picea sitchensis), western hemlock (Tsuga heterophylla), FRESH-deer model, understory diversity.
- Partial cutting of western hemlock and sitka spruce in southeast Alaska.
- Response of Sitka spruce and western hemlock to commercial thinning.
- Management of western Hemlock-sitka spruce forests for timber production.
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