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Metasequoia

 

Metasequoia

Metasequoia
Temporal range: 70.0–0 Ma
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Late Cretaceous to Recent
Scientific classification
Kingdom: Plantae
Division: Pinophyta
Class: Pinopsida
Order: Pinales
Family: Cupressaceae
Subfamily: Sequoioideae
Genus: Metasequoia
Miki, 1941
Species

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 Lichuan county in the Hubei province 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. Sequoioideae and several other genera have been transferred from the former Taxodiaceae family to Cupressaceae based on DNA analysis.[1]

Contents

  • Paleontology 1
  • Appearance 2
  • History 3
  • Metasequoia in gardens, parks and streets 4
  • References 5
  • Further reading 6
  • External links 7

Paleontology

Metasequoia redwood fossils are known from many areas in the Northern Hemisphere; more than 20 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.[2] 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 (northern Canada) at around 80° N latitude.[3] Metasequoia was likely deciduous by this time. Given that the high latitudes in this period were warm and tropical, it is hypothesized that the deciduous habit evolved in response to the unusual light availability patterns, not to major seasonal variations in temperature.[4] During three months in the summer, the sun would shine continuously, while three months of the winter would be complete darkness. It is also hypothesized that the change from evergreen to deciduous habit occurred before colonizing the high latitudes and was the reason Metasequoia was dominant in the north.[5]

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.

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

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 130–150 feet (40–45 m) tall and 6 feet (2 m) in trunk diameter in cultivation so far (with the potential to grow to even greater heights).

The leaves are opposite, 0.4-1.25 inches (1–3 cm) long, and bright fresh green, turning a foxy red-brown in fall. The pollen cones are 0.25 inch (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, 0.6-1.0 inches (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.

Metasequoia has experienced morphological stasis for the past 65 million years, meaning the modern Metasequoia glyptostroboides appears identical to its late Cretaceous ancestors.[6]

History

Eocene (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 species was discovered in China in Modaoxi (磨刀溪; presently, Moudao (谋道), in Lichuan County, Hubei[7]) 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.[7] A few trees are also said to exist in the neighboring Hunan Province.[7]

Metasequoia in gardens, parks and streets

Dawn redwoods are fast-growing trees. They will grow too large for small gardens, but can be good in a wide range of larger gardens and parks. Although they live in wet sites in their native habitat they will also tolerate dry soils.[8] Unlike most conifers, their deciduous habit means they do not cast too much shade in winter, and they can even be seen growing as street trees in London.

References

  1. ^ Paul A. Gadek, Deryn L. Alpers, Margaret M. Heslewood & Christopher J. Quinn (2000). "Relationships within Cupressaceae sensu lato: a combined morphological and molecular approach".  
  2. ^ A. Farjon (2005). Monograph of Cupressaceae and Sciadopitys.  
  3. ^ Christopher J. Williams, Arthur H. Johnson, Ben A. LePage, David R. Vann & Tatsuo Sweda (2003). forests. II. Structure, biomass, and productivity of Eocene floodplain forests in the Canadian Arctic"Metasequoia"Reconstruction of Tertiary ( 
  4. ^ Ralph W. Chaney (1948). on problems of Tertiary paleobotany"Metasequoia"The bearing of the living .  
  5. ^ Richard Jagels & Maria A. Equiza (2005). Competitive advantages of Metasequoia in warm high latitudes. pp. 335–349.  In (2005)et alLePage .
  6. ^ Ben A. LePage, Hong Yang & Midori Matsumoto (2005). The evolution and biogeographic history of Metasequoia. pp. 3–115.  In (2005)et alLePage .
  7. ^ a b c Gaytha A. Langlois (2005). in China Metasequoia A conservation plan for. pp. 367–418.   In (2005)et alLePage .
  8. ^ B.G. Hibberd, ed. (1989). Urban Forestry Practice, Forestry Commission Handbook 5. p. 61.  In Hibberd (1989).

Further reading

  • Zican He, Jianqiang Li, Qing Cai, Xiaodong Li & Hongwen Huang (2004). "Cytogenetic studies on Metasequoia glyptostroboides, a living fossil species".  
  • 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]
  •  
  • Christopher J. Williams, Ben A. LePage, David R. Vann, Takeshi Tange, Hiroyuki Ikeda, Makoto Ando, Tomoko Kusakabe, Hayato Tsuzuki & Tatsuo Sweda (2003). in Japan"Metasequoia glyptostroboides"Structure, allometry, and biomass of plantation ( 
  • Ben A. LePage, Christopher James Williams & Hong Yang, ed. (2005). MetasequoiaThe Geobiology and Ecology of. Topics in geobiology 22.  
  • B.G. Hibberd, ed. (1989). Urban Forestry Practice, Forestry Commission Handbook 5 (PDF).  

External links

  • The metasequoia organisation
  • Giant redwoods in the U.K.
  • "Metasequoia glyptostroboides".  
  • D.A. Hänks. "Crescent Ridge Dawn Redwoods Preserve". 
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