USDA Forest Service

Pacific Southwest Research Station

 
Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
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Publications and Products

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General Technical Report

Title: Natural range of variation of red fir and subalpine forests in the Sierra Nevada bioregion

Author: Meyer, Marc D.; North, Malcolm P.

Date: 2019

Source: Gen. Tech. Rep. PSW-GTR-263. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station

Station ID: GTR-PSW-263

Description: 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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Citation

  • Meyer, 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.
Last Modified: Sep 5, 2019 12:13:00 PM