glyptostroboides – resembling the genus Glyptostrobus (Chinese swamp cypress, water pine), of which living specimen was initially thought to be a member

Native range: SE and South-central China

Leaves:

• branchlets opposite (Taxodium distichum is alternate and less evenly spaced)
• linear, about 3/4–1” long
• soft light green
• 2 stomatal bands

Cones:

• male and female structures borne on different branches
• male cones in pairs on pendulous tassels (not found on young trees)
• female cones purplish black oblong (9 x 5.5 mm) when young, nearly spherical (1.4–2.5 x 1.6–2.3 cm) when mature
• pendulous, at end of branchlets or on long stalk ~5 cm
• scales – 12 pairs, opposite, decussate, peltate (shield-shaped)

Other characteristics:

• deciduous tree
• 70–100’, up to 160’ (50 m.) in China
• trunk w/ “armpits” (depression below lateral branches) on older trees
• fluted/buttressed trunk develops with maturity
• open and delicate branching pattern (not twiggy and messy)
• foliage emerges light green in spring, matures to deep green in summer and turns yellow then red-bronze in fall

Relevant info:

• evolved near the Arctic Circle during a period when lowland winter temperatures seldom went below freezing, so polar light seasonality could have been a driving force for the evolution of deciduousness in this species
• genus originally identified in the fossil record by a Japanese paleobotanist in 1941
• living members of genus identified by Chinese botanists in 1943
• seeds were sent to and grown by Missouri Botanic Garden and Univ. of California and Oregon in 1947
• more fascinating details of this story found at: OSU Landscape Plants – Metasequoia glyptostroboides
• “Dawn redwood” refers to the tree’s early fossil record
• State Fossil of Oregon, where it flourished 5 to 25 million years ago and can be found in the fossil record

Ecology & Adaptations:

• native to SE and south-central China
• found on moist sites, such as riparian habitats on valley floors and in moist ravine bottoms, wet lower slopes and montane river and stream valleys
• on acidic, montane yellow-earth soils in regions with moderate climate
• 750–1500 m.
• pollination:
  • by wind
  • male cones are aggregated in clusters situated at the ends of long, flexible branches
  • male and female cone emerge in Fed/Mar, and pollen release occurs before the leaves emerge, which reduces the pollen deposition and wastage caused by leaves and twigs
  • cones ripen in early December and shed their seeds in late Dec/early Jan
• seed dispersal – small, light, and winged make seeds ideal for wind dispersal
• seed germination:
  • best on open soils
  • may be limited by water availability
• herbivory defense – compounds (e.g., terpenes) produced in the tissues inhibit some mammal herbivory (e.g., cervids such as deer) and insect infestation
• insect & disease resistance:
  • resists insects and disease due to accumulation of toxic secondary compounds in tissues
  • oil in cones contains compounds (mono- and sesquiterpenes, norlignans) that inhibit fungal infection
  • aromatic compounds in heartwood resist fungal decay (houses built with this wood in China we said to have lasted 7 generations of farmers)
• tolerant of periodic flooding:
  • adapted to clay soil that is continually moist
  • buttresses/flutes may help stabilize trunk
  • wide, shallow root system may facilitate access to oxygen in air
• cold tolerance:
  • tree buds survive cold temperatures down to -30ºC
  • possibly through extraorgan freezing, i.e., scales act as an ice sink, with water moving from bud cells to scales and becoming supercooled
• mixed shade tolerance:
  • fast growing in full sun
  • capable of photosynthesizing at relatively low light levels (photosynthetic apparatus saturates at a relatively low level of light) yet does not tolerate suppression like most shade tolerant plants – i.e., once experiences suppression, will not respond to higher light levels
  • intolerant of high light level – chlorophyll content declines with increasing light intensity and the pigment rhodoxanthin increases, leading to a reddish cast in the upper leaves of the trees