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Scientific name: Picea koyamae Shirasawa 1913
Synonyms: -
Common names: Koyama's spruce (English), Yatsugatake-tohi (Japanese)
Tree to 20(-30) m tall, with trunk to 0.6(-0.8) m in diameter. Bark dark grayish brown, remaining flaky but also becoming shallowly furrowed at the base of large trees. Crown conical, fairly open and thinning further with age, with horizontal or gently rising branches bearing short horizontal or slightly hanging side branches. New branchlets yellowish brown to reddish brown, usually hairless, a little hairy in the grooves of weak side branchlets. Buds 6-8(-13) mm long, resinous. Needles green to a little bluish green with wax, (0.6-)1-2(-2.5) mm long, straight or curved, diamond-shaped, with two to five lines of stomates on each side, blunt to pointed. Pollen cones 10-25 mm long, red. Seed cones 4-8(-9.5) cm long, green or with a reddish tinge before maturity, ripening yellowish brown. Seed scales egg-shaped to nearly circular, thinly woody and stiff, seed body (2-)3-4 mm long, the wing 8-12 mm longer.
The species name honors Mitsuo Koyama (1885 - 1935), the Japanese botanist who discovered it in 1911, the last Japanese spruce species to be recognized, while the mainland stands were assigned incorrectly to various other previously described species. The name was originally published as "koyamai", but this is an orthographical error (spelling, typo, etc.) and it was corrected under the provisions of the Int.
Central Honshu (Japan), North Korea, and nearby China and Russia. Forming pure stands or mixed with other spruces and other montane conifers; (400-)1,100-2,000 m.
Red List Category & Criteria: Critically Endangered
Using recently published distribution maps, the extent of occurrence (EOO) of Picea koyamae has been calculated as less than 100 km². Historical events such as logging, fire, typhoons and landslides have led to relatively small, fragmented stands. Recent genetic studies indicate that there has been and is little genetic exchange between these populations. Changes in precipitation, snowfall, temperature, and the frequency of severe weather events associated with climate change is also having an effect on the quality of habitat and regeneration. There has been a reduction of the area of occupancy and there continues to be a loss of mature individuals. This species is therefore listed as Critically Endangered.
It occurs in a single population distributed on Mts Akaishi (most sites) and on MtsYatsugatake. On Mts Yatsugatake most mature trees are located in the subpopulations Fuki-sawa, Karamatsu-sawa and Senmai-iwa. It typically occurs in small, often isolated groups and there are estimated to be less than 1,000 mature individuals in total. Typically the number of mature individuals in each stand ranges from nine to 135 and the area of each stand can be between 0.5–11.5 ha with a mature tree density of about 10 individuals per ha. Some stands remain unknown due to their inaccessibility. Typically the subpopulations are often surrounded and isolated by plantations of Larix kaempferi which has contributed to low levels of gene flow.
In the Yatsugatake Mountains it is restricted to lava flows, while in the Akaishi Mountains it is sometimes found on soils on phylitic rocks, sandstone or more commonly on limestone. It forms small groups of trees in association with Larix kaempferi, Thuja standishii, Picea maximowiczii, Pinus koraiensis and Quercus mongolica var. grosseserrata. There is documentation of regeneration following coarse disturbance, for example the trees in the Yabu-sawa and Kaminigori-sawa sites in Todai-gawa location (Akaishi Mountains) regenerated after a rockslide about 100 years ago. Regeneration can also follow fires and logging.
The biggest threat to Picea koyamae over the last 100 years has been from logging and replanting with Larix kaempferi: this has led to fragmentation with its associated consequences. Loss of forest as a result of typhoons is also a contributing factor together with forest fires. Today the most serious problem is the decline in the number of mature individuals and the deterioration of the habitat which is having a serious impact on seedling establishment. Picea koyamae is a relictual species that is at the southern extremity of the range for the genus; as a result it has become vulnerable to climate change and is unable to adapt to environmental changes. In some locations (e.g., Tennyo-san) there is an absence of seedlings which is thought to be due to the effect of Sasa bamboo covering the forest floor and damage to seed by a chalcid wasp.
Historically it is thought that Picea koyamae was used for making furniture and for constructing houses.
In 1990, only one location was given protection but as a result of further research into the distribution of the species, six more areas have been designated as conservation areas. Further research is needed into the mode of natural regeneration.
Picea koyamae ’Albospica’ Picea koyamae ’Bedgebury Blue’ Picea koyamae ’Bedgebury Cascade’ Picea koyamae ’MPH Erdőtarcsa’ Picea koyamae ’Tenno’
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