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Swamp Cypress Family (Taxodiaceae)

Swamp Cypress Family (Taxodiaceae)

Characteristics

Members of the taxodiaceae

The swamp cypress family is more formally called the Taxodiaceae. This is a family of coniferous trees within the gymnosperms, that is, plants which produce naked seeds (not in a fruit) borne on scales. These scales are usually arranged to form a cone.

Within the Taxodiaceae some species are evergreen, and some deciduous. There are nine genera which contain 16 species. These can be found in temperate and subtropical regions, in both the Old and New Worlds. Only one genus is represented in the

Southern Hemisphere. Most of these are fast growing trees which can achieve a large size and an impressive age. Some members of this group have been known to be 3,000 years old.

Characteristics

all of the trees in this family produce resin when their branches are damaged. They all have one main trunk with a fibrous bark, usually of a reddish color. As the tree grows older the basal branches are lost, leaving a clear trunk. The leaves are usually dark green, needle like structures.

All of the Taxodiaceae are wind pollinated, with male and female reproductive structures on the same individual plant, but physically separate in different canes. The male part is a cluster of catkin-like cones which release pollen, which is then blown by the wind. The female cones are larger and occur singly or in groups, a drop of fluid is exuded from them on which pollen grains land. Once the pollen has been captured in this manner, the fluid is taken back in, bringing the pollen and ovule into close association so that pollination may occur. Some species are capable of reproducing very early in their life (e.g., Taxodium) while others must first achieve a few centuries of age (e.g., Taiwania).

The seeds are produced in mature cones, and when they are released from their high branches they can disperse over long distances due to the presence of wing-like, aerodynamic structures. Some, such as Sequoiadendron, only release their seeds after a forest fire, allowing a relatively competition-free start in life. The adult is little affected by the fire due to a protective layer of fibrous bark that is burnt off. However, the living wood underneath is not damaged, except by exceptionally severe fires.

Recognizable fossils of some of these species have been found from the Cretaceous and Tertiary eras.

The modern Taxodiaceae are found in warm temperate regions of the world, mostly in eastern Asia, east and west North America, and with a single genus in Tasmania. These plants favor areas of high rainfall with rich soil, tending to occur in local groves. One species, the swamp cypress (Taxodium distichum), is tolerant of wet conditions and will grow in swampy places.

Members of the taxodiaceae

Athrotaxis comprises three species found only on the islands of Taiwan in east Asia. It is possible that one species is a hybrid between the other two, due to its intermediate characteristics. These are moderately tall, pine-like trees.

Cunninghamia is a tall tree of great commercial importance in its native China and Taiwan. Two, rather similar species are known.

Another genus, with two or three species, is Taiwania, from China, Taiwan, and north Burma. These are felled for their timber, but they are rather scarce in their native habitats, provoking much concern among conservationist.

Cryptomeria is similar to the above groups, but the several species are more-widely spread in their native Japan and China. Due to the fast growing nature and height of this group, they have been widely introduced to other areas where they are important timber producers.

The big-tree or giant redwood (Sequoiadendron giganteum) produces the worlds most massive trees, with the tallest measured example being 344.5 ft (105 m) tall with a trunk diameter of 39 ft (12 m). These massive trees are native to California; they will not survive an intense frost and are intolerant of pollution. They are, however, remarkably fire tolerant due to their fibrous bark. In fact, disposal of their seeds is aided by fire, which makes the cones open, and also reduces competition for the new seedlings.

A closely related, and physically slightly taller genus is the coast redwood (Sequoia sempivirens), found naturally from southwest Oregon to California in small numbered groups.

All of the above genera are evergreens, that is, they do not lose all of their leaves in the autumn. The remaining members of the Taxodiaceae are all seasonally deciduous.

Perhaps the most endangered member of the whole group is the dawn redwood (Metasequoia glyptostroboides), which was found for the first time in 1941, in a small valley in Central China. No other wild populations have ever been discovered. The specific name is due to the initial physical similarity to the previous genus. While endangered in the wild, the dawn redwood can be cultivated and is widely grown.

Another endangered speciesendemic to China is Glyptostrobus pensilis. The swamp or bold cypress (Taxodium distichum) is a moderately hardy tree native to the southeastern United States. This species is not as massive as some of its relatives, but it is more hardy, and is a cultivated species. Two other Taxodium species are known.

See also Conifer; Gymnosperm; Sequoia.

Gordon Rutter

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Taxodiaceae

Taxodiaceae A family of conifers (or, according to some authors, a tribe of the family Pinaceae). The leaves are spirally arranged (not in opposite pairs as in Cupressaceae) and the leaves are evergreen, hard, and scale-, spine-, or awl-like in most genera, though in a few (e.g. Metasequoia and Taxodium) they are soft and deciduous. The cones are globular and hard, with the bracts completely fused to the ovule-bearing scales (as in Cupressaceae but unlike Pinaceae). The family consists of 10 genera and only 13 species. It includes many ancient relict monotypic genera, like Sequoiadendron, Sequoia, Metasequoia, and Cryptomeria, all of which have an extremely limited distribution as natives today though formerly they were mostly very widespread (epibiontics). They are widely cultivated in many temperate regions; for example, Sequoiadendron giganteum (wellingtonia or big tree), once widespread in the world in Pliocene times, is now confined as a native to the Sierra Nevada of California.

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