Metasequoia glyptostroboides

Metasequoia glyptostroboides
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Conservation status
Endangered (IUCN 3.1)
Scientific classification
Kingdom:	Plantae
Division:	Pinophyta
Class:	Pinopsida
Order:	Pinales
Family:	Cupressaceae
Subfamily:	Sequoioideae
Genus:	Metasequoia
Species:	M. glyptostroboides
Binomial name
Metasequoia glyptostroboides Hu and W.C.Cheng, 1948

Metasequoia glyptostroboides, the dawn redwood, is a fast-growing, endangered coniferous tree, the sole living species of the genus Metasequoia, one of three species in the subfamily Sequoioideae. It is native to Lichuan county in the Hubei province of China. Although shortest of the redwoods, it can grow to at least 200 ft (61 m) in height.

Metasequoia glyptostroboides (dawn redwood) bonsai tree

History

Though once common across the northern hemisphere, the Dawn Redwood was originally considered extinct. The genus Metasequoia was first described in 1941 as a fossil of the Mesozoic Era, and none of the fossils discovered were less than 1.5 million years old. Dr. Shigeru Miki (1901–1974), a paleobotanist from Kyoto University, identified a divergent leaf form while studying fossil samples of the family Cupressaceae and realized he was looking at a new genus, which he named Metasequoia, meaning "like a sequoia."

In the same year a forester named T. Kan came across an enormous living specimen while performing a survey in Sichuan and Hubei provinces. Though unaware of Miki’s new genus, he recognized the unique traits of the tree. It formed part of a local shrine, where villagers called it Shui-shan 水杉 or "water fir".

In 1943, Zhan Wang (1911–2000), a Chinese forestry official, collected samples from an unidentified tree in Modaoxi, China (presently, Moudao, Lichuan County, Hubei)—now believed to be the same tree Kan discovered. The samples were determined to belong to a tree yet unknown to science, but World War II postponed further study.

It wasn’t until 1946 that anyone connected Miki's genus and the living samples. Professors Wan Chun Cheng and Hu Xiansu made the pivotal connection and provided the specific epithet "glyptostroboides," after its resemblance to the Chinese swamp cypress (Glyptostrobus).

In 1948 the Arnold Arboretum of Harvard University funded an expedition to collect seeds from Kan's original tree and, soon after, distributed seeds and seedlings to various universities and arboreta worldwide for growth trials.

Related species

Together with Sequoia sempervirens (Coast Redwood) and Sequoiadendron giganteum (Giant Sequoia) of California, M. glyptostroboides is classified in the subfamily Sequoioideae of the family Cupressaceae. Although it is the only living species in its genus, three fossil species are known as well. The other Sequoioideae and several other genera have been transferred from the Taxodiaceae to the Cupressaceae based on DNA analysis.

Appearance

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  Dawn redwood foliage - note opposite arrangement

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  Pollen bearing cones

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  Young leaves

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  Young seed bearing cones

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  Mature seed bearing cones

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  Mature tree

While the bark and foliage are similar to another closely related genus of redwoods, Sequoia, M. glyptostroboides differs from the coast redwood in that it is deciduous, like Taxodium distichum (bald cypress). Similar to Taxodium, older trees may form wide buttresses on the lower trunk. Metasequoia is a fast-growing tree, exceeding 35 m (115 ft) in height and 1 m (3.3 ft) in trunk diameter by the age of 50, in cultivation (with the potential to grow to even greater dimensions). The trunk forms a distinctive "armpit" under each branch. The bark is vertically fissured and tends to exfoliate in ribbon-like strips.

The leaves are opposite, 1–3 cm (0.39–1.18 in) long, and bright fresh green, turning a foxy reddish brown in fall. The pollen cones are 5–6 mm (0.20–0.24 in) long, produced on long spikes in early spring; they are produced only on trees growing in regions with hot summers. The cones are globose to ovoid, 1.5–2.5 cm (0.59–0.98 in) in diameter with 16-28 scales arranged in opposite pairs in four rows, each pair at right angles to the adjacent pair; they mature in about 8–9 months after pollination.

Conservation

In Lichuan, Hubei, there is a dawn redwood forest consisting of barely 5,000 trees (by another count, around 5,400 trees.), and some smaller groups (typically, under 30 trees each). Since its discovery, the dawn redwood has become something of a national point of pride, and it is protected under Chinese law and also planted widely. However, it is still listed as endangered in the wild. Cutting of trees or branches is illegal, but the demand for seedlings drives cone collection to the point that natural reproduction is no longer occurring in the dawn redwood forest. The species will continue to live in yards, parks and on roadsides all over China, but the M. glyptostroboides forest ecosystem could disappear when its mature trees die.

Pizhou, Jiangsu boasts the Longest dawn redwood avenue in the world. The avenue is approximately 60 km long with over one million trees.

In 1995, the Crescent Ridge Dawn Redwoods Preserve (CRDRP) was established in North Carolina. Here, hundreds of dawn redwoods have been planted in a natural state where they can be observed and recorded in the wild, reducing the need for those in the U.S. to travel to China. The project goal is 1,000-5,000 trees. Currently, 200+ trees thrive in three separate groves. A fourth grove was lost to beaver depredation with loss of 125 or more trees. CRDRP remains the only eastern redwood forest in the U.S., and the sole wild dawn redwood forest outside of China. The preserve is tentatively scheduled to open to the public in 2035.

Cultivation

Since the tree's rediscovery in 1943, the Dawn redwood has become a popular ornamental tree in parks and gardens worldwide. It has gained the Royal Horticultural Society's Award of Garden Merit.

Dawn redwood has proved an easy tree to grow in temperate regions, and is now widely planted as an ornamental tree. Planted trees have already reached 25–40 m (82–131 ft) in height and 1–1.3 m (3.3–4.3 ft) in diameter, despite being in cultivation for less than sixty years. This rapid rate of growth has led to consideration for using the tree in forestry plantations. It has been discovered that M. glyptostroboides will thrive in standing water, much like Bald Cypress, and if left branched to the ground in full sun, will develop the large, contorted boles that have made it famous. Limbing or pruning at an early age will prohibit this formation later on.

In cultivation, M. glyptostroboides is hardy to USDA Zone 5, making it hardy down to lows of -25 °F (-32 °C). It is tolerant of soggy, waterlogged soils; in the wild it is adapted to growing on flood plains. Until it is established in a specific site, it is prone to drought and inadequate water availability. The Dawn redwood is recommended for urban areas in the Midwest, Southeast, and East Coast of North America, as its fast growth rate and tolerance for air pollution make it widely adaptable and able to thrive where other species might suffer. This species tends to struggle without irrigation in arid climates such as the American West unless planted directly on or adjacent to a body of water such as a pond or stream. This species is also highly susceptible to damage from contact with heavy amounts of winter de-icing salt.

In the late 1980s, it was discovered that many of the second generation trees in cultivation suffered from inbreeding depression (extremely low genetic variability) which could lead to increased susceptibility to disease and reproductive failure. This was because most of the trees were grown from seeds and cuttings derived from as few as three trees that the Arnold Arboretum had used as its source. More widespread seed-collecting expeditions in China in the 1990s sought to resolve this problem and restore genetic diversity to cultivated M. glyptostroboides.

In the United Kingdom

The Dawn redwood can be found in some gardens of mansion houses and historic buildings. Bank Hall in Bretherton has two individuals believed to have been brought over many years ago from China and now under conservation protection. They are thought to have been a present from Kew Gardens in London to one of the families that lived at the hall. Nevill Hall Hospital, built on the grounds of a mansion, has a stand of ten trees planted adjacent to the Pathology Laboratory. Three trees are at Croxteth Hall in Liverpool.

There are also trees on the grounds of Askham Bryan College (York), the Arboretum Trust (York), Dulwich Picture Gallery (South London), a large tree growing near to the Thames in Richmond (London), and Hyde Park (London) - at the eastern end of the Serpentine Lake, described by its plaque as a Water Fir. Cambridge University Botanic Garden has at least two tall dawn redwood trees, which were planted in 1949, and both St John's College and Downing College harbour dawn redwoods in their grounds.

There are two specimens growing in Belle Vue Park, Newport City, South Wales, UK, not far from Neville Hall Hospital above. One specimen is on the grounds of Pinderfields Hospital, Wakefield, Yorkshire.

In the United States

Dawn redwoods thrive over a large, crescent-shaped region that encompasses the eastern and southern United States. Many institutions, such as the Arnold Arboretum of Harvard University have fine specimens, but the Crescent Ridge Dawn Redwoods Preserve in North Carolina remains the only endeavor for the re-introduction of the species into a natural setting in the US.

There is a small grove of Dawn Redwoods at Bailey Arboretum in Locust Valley, NY, including one tree which is claimed to be the world's largest by diameter. And the New York City Department of Parks and Recreation has begun planting Dawn Redwoods on sidewalks throughout Manhattan and Brooklyn.

See also

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  Displaying autumn foliage in Victoria, BC, Canada

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  The trunk of an adult tree

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  The base of the trunk.

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  Pollen (a.k.a. "male") cones

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  A specimen at Croxteth Hall in Liverpool: summer foliage

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  Same specimen: autumn foliage

Further reading

• He, Zican, Jianqiang Li, Qing Cai, Xiaodong Li, and Hongwen Huang. 2004. "Cytogenetic Studies on Metasequoia Glyptostroboides, a Living Fossil Species". Genetica. 122, no. 3: 269-276.
• International Metasequoia Symposium, Ben A. LePage, Christopher J. Williams, and Hong Yang. The Geobiology and Ecology of Metasequoia. Topics in geobiology, v. 22. Dordrecht: Springer, 2005. ISBN 1-4020-2764-8
• Proceedings of the Second International Symposium on Metasequoia and Associated Plants, August 6–10, 2006, Metasequoia: Back from the Brink? An Update. Edited by Hong Yang and Leo J. Hickey. Bulletin of the Peabody Museum of Natural History, Volume 48, Issue 2 31 October 2007, pp. 179–426. [1]
• Bartholomew, Bruce, D. E. Boufford, and S. A. Spongberg. "Metasequoia glyptostroboides--Its present status in central China." Journal of the Arnold Arboretum 64.1 (1983): 105-128.
• Listed as Endangered B1ab(iii,v), v 3.1
• Farjon, A. (2005). Monograph of Cupressaceae and Sciadopitys. Royal Botanic Gardens, Kew. ISBN 1-84246-068-4.
• Hanks, D.A. Crescent Ridge Dawn Redwoods Preserve (2005). http://www.dawnredwood.org
• Jahren, A. H. & Sternberg, L. S. L. (2003). Humidity estimate for the middle Eocene Arctic rain forest. Geology May 2003 pdf file
• Metasequoia stumps, Axel Heiberg Island PDF (804 KB)
• Williams C.J., LePage, B.A., Vann D.R., Tange, T., Ikeda, H., Ando, M., Kusakabe, T., Tsuzuki, T. and T. Sweda. (2003). Structure, allometry, and biomass of plantation Metasequoia glyptostroboides in Japan. Forest Ecology and Management, 180(103): 287-301. [2]
• Williams C.J., Johnson A.H., LePage, B.A., Vann D.R. and T. Sweda. 2003. Reconstruction of Tertiary Metasequoia Forests II. Structure, Biomass and Productivity of Eocene Floodplain Forests in the Canadian Arctic. Paleobiology, 29(2): 271-292. [3]

External links

• Metasequoia in The Gymnosperm database
• Crescent Ridge Dawn Redwoods Preserve
• The metasequoia organisation
• More information on the Dawn Redwood, including largest specimens
• Giant redwoods in the U.K.