Metasequoia

This article is about the redwood genus, Metasequoia. For software, see Metasequoia (software).

Metasequoia Temporal range: 70.0–0 Ma PreЄ Є O S D C P T J K Pg N Late Cretaceous to recent
Conservation status
Critically Endangered (IUCN 2.3)
Scientific classification
Kingdom:	Plantae
Division:	Pinophyta
Class:	Pinopsida
Order:	Pinales
Family:	Cupressaceae
Subfamily:	Sequoioideae
Genus:	Metasequoia Miki, 1941
Species
†Metasequoia foxii Metasequoia glyptostroboides †Metasequoia milleri †Metasequoia occidentalis †Metasequoia disticha

Metasequoia (dawn redwood) is a fast-growing, deciduous tree, and the sole living species, Metasequoia glyptostroboides, is one of three species of conifers known as redwoods. It is native to the Sichuan-Hubei region of China. Although the least tall of the redwoods, it grows to at least 200 feet (60 meters) in height. Local villagers refer to the original tree from which most others derive as Shui-sa, or "water fir", which is part of a local shrine. Since that tree's rediscovery in 1944, the dawn redwood has become a popular ornamental.

Together with Sequoia sempervirens (coast redwood) and Sequoiadendron giganteum (giant sequoia) of California, Metasequoia is classified in the Cupressaceae subfamily Sequoioideae. Although M. glyptostroboides 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 former Taxodiaceae family to Cupressaceae based on DNA analysis.^[1]

Paleontology

Metasequoia redwood fossils are known from many areas in the Northern Hemisphere; more than twenty fossil species have been named (some were even identified as the genus Sequoia), but are considered as just three species, M. foxii, M. milleri, and M. occidentalis (Farjon 2005). During the Paleocene and Eocene, extensive forests of Metasequoia occurred as far north as Strathcona Fiord on Ellesmere Island and sites on Axel Heiberg Island ^[2] (northern Canada) at around 80°N latitude. Large petrified trunks and stumps of the extinct Metasequoia occidentalis (sometimes identified as Sequoia occidentalis) also make up the major portion of Tertiary fossil plant material in the badlands of western North Dakota in the United States.

The trees are well known from late Cretaceous to Miocene strata, but no fossils are known after that. Before its discovery, the taxon was believed to have become extinct during the Miocene; when it was discovered extant, it was heralded as a "living fossil".

Appearance

Dawn redwood foliage - note opposite arrangement

Displaying autumn foliage in Victoria, BC, Canada

While the bark and foliage are similar to another closely related redwood genus Sequoia, Metasequoia differs from the California redwood in that it is deciduous like Taxodium distichum (Bald Cypress), and like that species, older specimens form wide buttresses on the lower trunk. It is a fast-growing tree to 40-45 m tall and 2 m trunk diameter in cultivation so far (with the potential to grow to even greater heights).

The leaves are opposite, 1-3 cm long, and bright fresh green, turning a foxy red-brown in fall. The pollen cones are 5-6 mm long, produced on long spikes in early spring; they are only produced on trees growing in regions with hot summers. The cones are globose to ovoid, 1.5-2.5 cm 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.

History

Ypresian age M. occidentalis branchlet

Metasequoia was first described as a fossil from the Mesozoic Era by Shigeru Miki in 1941, but in 1944 a small stand of an unidentified tree was discovered in China in Modaoxi (磨刀溪; presently, Moudao (谋道), in Lichuan County, Hubei^[3]) by Zhan Wang. Due to World War II, these were not studied further until 1946 and only finally described as a new living species of Metasequoia in 1948 by Wan Chun Cheng and Hu Hsen Hsu. In 1948 the Arnold Arboretum of Harvard University sent an expedition to collect seeds and, soon after, seedling trees were distributed to various universities and arboreta worldwide for growth trials.

Presently, a number of natural Metasequoia populations exist in the hills and wetlands of Hubei's Lichuan County. Most of them are small, with fewer than 30 trees each; however, the largest of them, in Xiaohe Valley, is estimated to consist of around 5,400 trees. ^[3] A few trees are also said to exist in the neighboring Hunan Province.^[3]

References

1. ^ Gadek, P.A., Alpers, D.L., Heslewood, M.M., and Quinn, C.J. (2000). Relationships within Cupressaceae sensu lato: A combined morphological and molecular approach. American Journal of Botany, 87(7): 1044-1057.
2. ^ http://edisk.fandm.edu/chris.williams/pubs/williams_etal_2003b.pdf
3. ^ ^{a b c} Langlois, Gaytha A. (2005), "A conservation plant for Metasequoia in China", in LePage, Ben A.; Williams, Christopher James; Yang, Hong, The geobiology and ecology of Metasequoia, Volume 22 of Topics in geobiology, Springer, p. 369, ISBN 1402026315, http://books.google.com/books?id=JfiWU-1GSqEC&pg=PA369 

• 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 Glyptostroboides". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=505864. Retrieved September 25, 2006. 
• 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. [1]
• 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. [2]

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 1402027648
• 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. [3]
• The Reports of the Third International Metasequoia Symposium, August 3 to 8, 2010, Osaka, Japan [4]

External links

• Metasequoia in The Gymnosperm database
• The metasequoia organisation
• Giant redwoods in the U.K.
• [5]