California’s Rarest Conifer?

CNPS teams with the Klamath National Forest to map yellow-cedar (Callitropsis nootkatensis) in California

CNPS has begun a collaborative mapping and inventorying project for yellow-cedar in California. The species is a CNPS Inventory of Rare and Endangered Plants on list 4.3 (limited distribution) in the state, with only a handful of known locations. The majority of the stands are on the Klamath National Forest but a few are also on the Six Rivers. Over the course of summer 2017, Michael Kauffmann and Julie Evens will be visiting a number of these populations and collecting data on stand health, reproduction, and plant associations. The week of July 5-6 we visited the world’s southern-most stand, deep in the Siskiyou Wilderness.

This project was initiated by Forest Service Region 5 when we were contacted by Brian Buma from University of Alaska. His research is showing that yellow-cedar at the northern extent of its range is in declining health and not reproducing. The baseline data we collect this summer will inform future studies across the range of this species.

Yellow-cedar (Callitropsis nootkatensis)

This common tree of Alaska and British Columbia south to northern Oregon is represented in California by a few small, isolated groves. In the southern extent of its range, yellow-cedar has a unique ecological amplitude compared to habitats further north. Over most of Alaska and Canada, it is a tree of the coastal mountains, growing from sea level to 3000’. But as the species ranges southward into southern Washington and Oregon it moves upslope into cool, wet, rocky, north-facing glades where subalpine conditions prevail. This is also the case in the Siskiyou Mountains, where it is a true relict, surviving in a handful of specific microsites that maintain a cool wet climate. Yellow-cedar trees do not reach significant size in the Siskiyous—rarelymore than ~70’ tall . Although lacking size, all southern stands maintain healthy populations. They often form impenetrable, low-growing thickets along entire rocky washes between subalpine lakes.

Other “cedars” in the region that overlap in habitat with yellow-cedar have a leaf silhouette that can be described as lacy or flattened (Port Orford-cedar) and vertical (incense-cedar). With yellow-cedar the droopy foliage falls from a distinctly conical crown in a definable pattern, creating a wet and tired look. The drooping is an effective adaptation to slough off weighty winter snow without branch breakage.

Where the species overlaps with other cedars, Port Orford-cedar can be distinguished by stomatal bloom in the shape of an X on the underside of the needles while yellow-cedar has no bloom. The spherical cones are similar to those of Port Orford-cedar, but yellow-cedar has fewer than six cone scales, while Port Orford-cedar has more than six. The unopened cone looks like an armored ball because the end of each scale presents a sharply tipped umbo. Most of the year cones remain closed, like cypresses. Though cone production does not occur every year, one may find remnants on the ground from previous years—which will greatly aid with proper identification. The bark is similar to the North American cypresses but thinner. Only the juvenile bark characteristics are important in the region because trees do not get very old (or big) here—gray to brown to rarely black between scaly or shallow ridges. In the Siskiyou Mountains these three “cedars” all occur, sometimes together, making identification challenging. The real challenge lies in finding a location where the regionally uncommon yellow-cedars still survive.