Natural range of variation of red fir and subalpine forests in the Sierra Nevada BioregionAuthor(s): M. Meyer; Malcolm North
Source: Gen Tech. Rep. PSW-GTR-263. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station
Publication Series: General Technical Report (GTR)
Station: Pacific Southwest Research Station
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Comparisons between historical and current conditions indicate that modern red fir (Abies magnifica) and subalpine forests of the Sierra Nevada bioregion are largely within their natural range of variation (NRV) with respect to compositional, functional, and some structural variables. Exceptions common to both forest types include a considerable shift in the tree size class distribution to smaller diameters, decrease in large-diameter tree densities (e.g., red fir, lodgepole pine [Pinus contorta], western white pine [P. monticola]), and greater homogenization of forest structure at both stand and landscape scales. Red fir forests had an increase in tree cover in lower canopy strata, and a lengthening of fire return intervals and fire rotations during much of the 20th century. Subalpine forests had increases in treeline growth and recruitment, and a marginal lengthening of fire return intervals and fire rotations during much of the 20th century. For both forest types, fire frequency and severity, moisture stress, the incidence of pathogens and insects, and tree mortality rates are projected to increase and likely exceed the NRV with climate change. Climate envelope models consistently project a substantial loss in suitable habitat or high climate vulnerability of both red fir and subalpine forests in the Sierra Nevada bioregion by the end of the 21st century, suggesting that the greatest changes in these forests in the coming decades will occur as a direct or indirect consequence of climate change.
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CitationMeyer, Marc D.; North, Malcolm P. 2019. Natural range of variation of red fir and subalpine forests in the Sierra Nevada bioregion. Gen Tech. Rep. PSW-GTR-263. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 135 p.
KeywordsAbies magnifica, climate change, forest ecology, natural range of variation, historical range of variation, red fir, Sierra Nevada, subalpine forests
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