Dawn redwood  (Metasequoia glyptostroboides)

Classified as Critically Endangered (CR) on the IUCN Red List (1).

Considered one of the greatest botanical finds of the 20^thcentury, the dawn redwood was known only from ancient fossils, until a small population was discovered in the forests of Central China in 1944 (3).  Dubbed a ‘living fossil’, this coniferous tree grows with an orange-brown, thick, tapering trunk and a broad, buttressed base (4).  Displaying the characteristic conifer shape, the dawn redwood has a narrow, pyramidal foliage with sparse, upward-sweeping branches, and straight, needle-like leaves.  Green in the spring and summer, the leaves of this deciduous tree turn a vibrant reddish-brown before falling to the ground in autumn (5).  The dawn redwood is a monoecious species, and light yellow-brown male cones hang in clusters, while yellow-green female cones hang individually (6).

Restricted to the Sichuan, Hubei and Hunan Provinces in Central and Southeast China, the dawn redwood has an extremely small and fragmented range (1).

The dawn redwood grows in open forests, preferring shady, moist areas, such as ravines and stream banks (1) (4).

The dawn redwood is a monoecious species, meaning the male and female reproductive organs are borne on the same tree. In common with other conifers, the dawn redwood produces pollen and ovules inside separate male and female cones.  Pollen is transferred to the female cones by wind, initiating pollination.  Small, winged seeds subsequently develop inside the cone, which splits when ripe, allowing wind to disperse the seeds across the landscape (7).  In favourable habitat, the dawn redwood may grow up to 80 centimetres per year, reaching incredible heights over 40 metres, with a lifespan of over 100 years (2) (4).     

Existing in several fragmented, relict populations, the largest of which numbered only around 120 mature trees in 2006, the dawn redwood is one of Asia’s rarest trees (1). Since its discovery the species has been protected, with initial measures focussing on protecting individual trees rather than whole populations. Although this prevented the species from direct threats, through agricultural encroachment and firewood collecting, the natural habitats surrounding dawn redwood trees have been severely degraded. In place of natural forests with a diversity of tree species, forests dominated by dawn redwood trees have arisen. This has had the adverse affect of providing ideal conditions for insect pest species to thrive, while the largest, oldest trees are more vulnerable to lightening strikes (8). 

An additional threat to this species is pollution from coal burning households. The population in the Xiaohe Valley is now eight times larger than it was when the dawn redwood was first discovered, with the local community increasingly changing from burning firewood to coal. Those dawn redwood trees closest to such households shed their leaves earlier and also produce less fruit than those in more isolated locations (8). Furthermore, the dawn redwood appears to have a low genetic diversity as a direct result of its low population number (9) (10).

With a small population, and a highly fragmented distribution, the survival of the dawn redwood is dependant upon the successful implementation of conservation measures (1).   Recognising this, the Chinese government gave the dawn redwood protected status in 1980, while ex-situ nurseries have also been established with the aim of increasing the species’ genetic diversity (9) (10). A number of reserves have been created to protect the remaining trees and it has been recommended that the largest and oldest trees should receive additional protection. It has also been recommended that the natural plant communities that were original associated with this species should be restored, and that lightening conductors should be attached to the largest trees (8) (11).   

For more information on tree conservation, see: 

• The Global Trees Campaign: 
  http://www.globaltrees.org/

For more information on the dawn redwood, see: 

• The Gymnosperm Database: 
  http://www.conifers.org/cu/me/index.htm