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Thuja plicata

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Taxonomy [top]

Kingdom Phylum Class Order Family
PLANTAE TRACHEOPHYTA PINOPSIDA PINALES CUPRESSACEAE

Scientific Name: Thuja plicata
Species Authority: Donn ex D.Don
Common Name/s:
English Western Red-cedar, Pacific Red-cedar, Giant Cedar, Giant Arbor-vitae, Shinglewood, Canoe Cedar

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2013
Date Assessed: 2011-04-27
Assessor/s: Farjon, A.
Reviewer/s: Stritch, L. & Thomas, P.
Justification:

Despite extensive logging, the extensive range and abundance of Thuja plicata makes it ineligible for any threatened category and it is therefore assessed as Least Concern.

Geographic Range [top]

Range Description: Recorded from western North America: along the Pacific Coast Range and Cascade Range from S Alaska to N California and in the N Rocky Mountains from British Columbia to Idaho and W Montana. Canada: Alberta, British Columbia; USA: Alaska, California, Idaho, Montana, Oregon, Washington. Both the extent of occurrence and area of occupancy are beyond the thresholds for a threatened category.
Countries:
Native:
Canada (Alberta, British Columbia); United States (Alaska, California, Idaho, Montana, Washington)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The global population is thought to be stable.
Population Trend: Stable

Habitat and Ecology [top]

Habitat and Ecology: The two more or less disjunct areas in which this species occurs: Pacific coastal mountains and Rocky Mountains, experience a different climate and therefore sustain different forest types. The mostly much wetter (winter rainfall, up to 6,600 mm p.a.) and milder coastal ranges support the tallest conifer forests in the world, with Sequoia sempervirens in the southern part exceeding 110 m and with Abies grandis to 80 m, A. procera 85 m, Picea sitchensis 87 m, Pinus lambertiana 75 m, Pseudotsuga menziesii 100 m, and Tsuga heterophylla to 80 m tall. Many of these trees also exceed any of their congeners elsewhere in overall size (Van Pelt 2001). Thuja plicata, with max. 75 m, is one of the longest-lived in these forests, with veteran trees often in excess of 1,000 years. Other conifers in these coastal forests are Chamaecyparis lawsoniana (extreme southern part of range), Xanthocyparis nootkatensis, Calocedrus decurrens, Abies amabilis, Pinus monticola, Tsuga mertensiana, and Taxus brevifolia in the understorey. Common angiosperm trees are Acer macrophyllum, Alnus rubra along rivers, and Populus trichocarpa; in the shrub layer are especially abundant Vaccinium spp., Rubus spectabilis and Ribes bracteosum. Deep layers of mosses and liverworts cover the forest floor and lower sections of tree trunks as well as fallen logs, on which latter most conifers find the only substrate to germinate. In the interior Abies grandis, A. lasiocarpa, Larix occidentalis, Picea engelmannii, P. glauca, Pinus contorta, P. ponderosa, Pseudotsuga menziesii var. glauca, and Taxus brevifolia are the most commonly associated conifers. Here annual precipitation does not exceed 1,200 mm and winters are much colder than along the coast. The altitudinal range of this species is 1-2,100(-2,300) m a.s.l. It grows on a wide range of soil types over nearly all available geological formations.
Systems: Terrestrial

Threats [top]

Major Threat(s): This species is common especially in the coastal sections of its extensive range and somewhat less so in the interior parts. (Selective) logging of mature trees and 'old growth' forest in which this species is a codominant continues in many areas where the forest is not on protected land. In situations where secondary forest growth is managed to favour other species (e.g. Pseudotsuga menziesii), this would lead to a decrease of occupancy of Thuja plicata. Plantation forestry focusing on this species should eventually reduce the level of exploitation of natural stands, in particular in 'old growth' forest with its high ecological value. At present this species is not considered to be in danger of extinction.

Conservation Actions [top]

Conservation Actions: This species is present in many protected areas, including some famous National Parks in both Canada and the USA.
Citation: Farjon, A. 2013. Thuja plicata. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 25 April 2014.
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