Dawn redwood
New species are frequently discovered, although few new plant species capture people's imaginations. One discovery that eventually captivated people was of a tall, deciduous, coniferous tree collected by Chinese foresters in East Sichuan (now Chongqing) in 1941. The tree was unknown in China and botanists started to consider that it might be a close relative of a genus described from Japanese fossils in the same year as the original collection. Collection expeditions were organized after the Second World War to the area of the original collection and more trees were found. Importantly, for the species' future, seed collections were made. By the end of the 1940s, the dawn redwood had been described scientifically, its similarity to the Japanese fossils determined and its cultivation worldwide begun.
The romance of the discovery of dawn redwood, its portrayal as a 'living fossil', its ease of propagation and its year-round, splendid appearance meant the tree soon became a popular ornamental tree outside China. A tree raised from one of the original Chinese seed collections is growing in the Oxford Botanic Garden.
The dawn redwood is the only living member of the genus Metasequoia. The fossil record of the genus shows it was distributed through North America and Eurasia up to 100 million years ago. Today, dawn redwood is restricted to the border of two Chinese provinces and Chongqing in Central China. The natural habitat of the dawn redwood is difficult to piece together from the fragments of riperine forest within which it is currently found. Traditionally, Chinese farmers in the area of its discovery used dawn redwood for construction and firewood. More recently, dawn redwood has become popular in cultivation, as elsewhere in the world. Of course, cultivation of dawn redwood also makes it difficult to identify unequivocally wild individuals.
The dawn redwood is a story of successful ex situ conservation. However, most of the plants in cultivation are derived from the original collections in the 1940s. Consequently, the trees have limited genetic diversity and hence capacity to adapt to changing conditions. In the wild, the tree is recognized internationally as endangered since its populations are declining. Individual wild dawn redwood trees are protected in China but the loss of habitat, as land use changes under pressures from the increasing human population, means that wild seedlings have few places to live. Dawn redwood may become another species saved from extinction but only in cultivation.
Further reading
Farjon A 2010. A handbook of the world's conifers. Vol. 1. Brill.
Farjon A and Filer DF 2013. An atlas of the world's conifers. Brill.
Ma J 2003. The chronology of the 'living fossil' Metasequoia glyptostroboides (Taxodiaceae): a review (1943-2003). Harvard Papers in Botany 8: 9-18.
Stephen Harris