Monday, 10 February 2020

METASEQUOIA GLYPTOSTROBOIDES

Metasequoia glyptostruboides, Dawn Redwood
Metasequoia (dawn redwood) is a fast-growing, deciduous tree native to Lichuan county in Hubei province in central China. It is the sole living species of Metasequoia glyptostroboides and one of three species of conifers known as redwoods.

Metasequoia has experienced morphological stasis for the past 65 million years: the modern Metasequoia glyptostroboides appears identical to its late Cretaceous ancestors.

Though static, they are remarkably similar to and sometimes mistaken for Sequoia at first glance. They are easily distinguishable if you look to their needles. Metasequoia has paired needles that attach opposite to each other on the compound stem. Sequoia needles are offset and attach alternately.

Although the least tall of the redwoods, it grows to at least Sixty meters (200 feet) 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 its rediscovery in 1944, the dawn redwood has become a popular ornamental tree in the Pacific Northwest.

Metasequoia fossils are known from many areas in the Northern Hemisphere. And folk love naming them. More than twenty fossil species have been named over time —  some even identified as the genus Sequoia in error — but for all their collective efforts to beef up this genus there are just three species: Metasequoia foxii, Metasequoia milleri, and Metasequoia occidentalis.

Alder & Metasequoia Fossils from McAbee
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.

We find lovely examples of Metasequoia occidentalis in the Eocene outcrops at McAbee near Cache Creek, British Columbia, Canada. The McAbee Fossil Beds are known for their incredible abundance, diversity and quality of fossils including lovely plant, insect and fish species that lived in an old lake bed setting 52-53 million years ago.

The McAbee fossil beds are 30 metres of fossiliferous shale in the Eocene Kamloops Group. The fossils are preserved here as impressions and carbonaceous films.

We see gymnosperm (16 species); a variety of conifers (14 species to my knowledge); two species of ginkgo, a large variety of angiosperm (67 species); a variety of insects and fish remains, the rare feather and a boatload of mashed deciduous material. Nuts and cupules are also found from the dicotyledonous Fagus and Ulmus and members of the Betulaceae, including Betula and Alnus.

We see many species that look very similar to those growing in the Pacific Northwest today. Specifically, cypress, dawn redwood, fir, spruce, pine, larch, hemlock, alder, birch, dogwood, beech, sassafras, cottonwood, maple, elm and grape. By far, we see the lovely Metasequoia the most.

Metasequoia was first described as a fossil from the Mesozoic Era by Shigeru Miki in 1941. Later 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 province by Zhan Wang.

Hubei province, central China.
While the find was exciting, it was overshadowed by China's ongoing conflict. In 1937, a clash between Chinese and Japanese troops at the Marco Polo Bridge, just outside Beijing, led to an all-out war.

A year later, by mid-1938, the Chinese military situation was dire. Most of eastern China lay in Japanese hands: Shanghai, Nanjing, Wuhan. Many outside observers assumed that China could not hold out, and the most likely scenario was a Japanese victory over China.

Yet the Chinese hung on, and after Pearl Harbor, the war became genuinely global. The western Allies and China were now united in their war against Japan, a conflict that would finally end on September 2, 1945.

With World War II behind them, the Chinese researchers were able to re-focus their energies on the sciences. In 1946, Wan Chun Cheng and Hu Hsen Hsu went back to examine the trees from Lichuan County. Two years later, they published a paper describing a new living species of Metasequoia. That same year, 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.