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12 Days of Conifers: Red Firs in the Forest

It’s Day 6 of 12 Days Of Conifers, and we’ve got a wintry scene in a red fir forest--a forest that likely looked very different a century ago.

Snowy forest with red firs
Red firs in the Sierra Nevada

Red fir (Abies magnifica) is widespread in the mountains in California, occurring throughout the Sierra Nevada as well as in the northern Coast Ranges, Cascade Range, and Klamath Range, dipping into parts of Oregon and Nevada as well.

Red fir gets its name from the red color seen in the deeply fissured bark of old trees. Unlike the pines, which have needles in bundles, firs have their short needles attached singly to branches. Though the red firs people use as Christmas trees are quite small, this species can reach nearly 200 feet.

Another way that red fir differs from many of the pines of California is in its ecology: red fir is more shade tolerant and less fire and drought resistant than trees like ponderosa pine, especially when they are young. Historically, shade-tolerant species like red fir would have been less abundant in mid-elevation mixed-conifer forests, because frequent low-severity fires would kill young firs. However, fire suppression over the course of the past century has allowed shade-tolerant species like red fir to increase in abundance. Increased densities of shade-tolerant trees can make it more likely that when a wildfire does occur, it will spread from the ground into the tree crowns, leading to a much more intense and severe fire.

Red fir is one of several species that USGS monitors for long-term population trends, and to find out what drives its dynamics.

Learn more about USGS forest ecology research here.

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A woman wraps a tape measure around a tree in the forest
This is Teodora Rautu. She is a Biological Science Technician on the field crew for USGS Western Ecological Research Center's Sierra Nevada Forest Dynamics project.  She is measuring the diameter of a red fir and trying to navigate the tape through the branches.  All of the trees in the Sierra Nevada Forest Dynamics plots are measured every 5 years, not only for determining the size of the trees but also for tracking tree growth rates.