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Tsuga mertensiana

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Taxonomy [top]

Kingdom Phylum Class Order Family
PLANTAE TRACHEOPHYTA PINOPSIDA PINALES PINACEAE

Scientific Name: Tsuga mertensiana
Species Authority: (Bong.) Carrière
Infra-specific Taxa Assessed:
Common Name/s:
English Mountain Hemlock
Synonym/s:
Pinus mertensiana Bong.
Taxonomic Notes: Two subspecies are recognized: the typical subspecies and subsp. grandicona Farjon from California and Nevada. This latter subspecies is not recognized as distinct in the USA. Both subspecies are assessed as Least Concern. An additional variety (var. jeffreyi) is recognized in Farjon (2010); this is treated by others as a hybrid species (Eckenwalder 2009). Its status is unclear, as it is largely known from cultivation but rarely if ever reported from the wild. This taxon is excluded in this assessment. The typical subspecies is also not assessed separately as its assessment is similar to that of the species as a whole.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2013
Date Assessed: 2011-04-28
Assessor/s: Farjon, A.
Reviewer/s: Thomas, P. & Stritch, L.
Justification:
The vast range of this species and its minor importance as a timber tree ensures its status as Least Concern well into the future.

Geographic Range [top]

Range Description: Occurs in the Pacific Coast Region of NW North America: from Alaska to California, in the Cascade Range and Sierra Nevada, and isolated occurrences in the northern Rocky Mountains. Both extent of occurrence and area of occupancy are beyond the thresholds for any threatened category.
Countries:
Native:
Canada (British Columbia); United States (Alaska, California, Oregon, Washington)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: In several areas, e.g. in the Coast Mountains of British Columbia, the Olympic Mountains of Washington, and in Lassen Volcanic National Park (Cascades), this species is invading subalpine meadows and late-lying snow basins. In some areas this has been going on for 150 years or longer, in other areas it seems to have begun more recently. The warming climate is likely responsible.
Population Trend: Increasing

Habitat and Ecology [top]

Habitat and Ecology: Tsuga mertensiana is a subalpine species, occurring from near sea level in Alaska to 1,500 m a.s.l. along the coast; in the Cascade Range between 1,200 m and 2,100 m a.s.l., and in the Sierra Nevada (subsp. grandicona) between 1,800 m and 3,350 m a.s.l. It grows on a variety of non-calcareous acidic soils, sometimes on peat, more commonly on mor humus (pH 3.1-3.9). Subsp. mertensiana is restricted to a climatic zone with high precipitation, in British Columbia between 2,000 mm and 4,000 mm per year, with long, snowy winters and short, cool summers. Subsp. grandicona grows in a much drier climate, but there primarily on high, N-facing slopes. The species is a major component of the Mountain Hemlock-Subalpine Fir forest, occurring in pure stands or mixed with Abies lasiocarpa, locally also with A. amabilis, Picea glauca, P. sitchensis, P. engelmannii (Rocky Mts.), Pinus spp., Tsuga heterophylla, Xanthocyparis nootkatensis, Juniperus occidentalis, and Betula papyrifera.
Systems: Terrestrial

Threats [top]

Major Threat(s): No threats have been identified for this species.

Conservation Actions [top]

Conservation Actions: This species occurs in several protected areas, among which are famous national parks.
Citation: Farjon, A. 2013. Tsuga mertensiana. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 20 April 2014.
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