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Taxodium distichum

Taxodium distichum (Baldcypress, Bald Cypress, or Swamp Cypress) is a species of conifer native to the southeastern United States.

Characteristics

It is a large tree, reaching 25–40 m (rarely to 44 m) tall and trunk diameter of 2–3 m, rarely to 5 m. The bark is gray-brown to red-brown, shallowly vertically fissured, with a stringy texture. The leaves are borne on deciduous branchlets that are spirally arranged on the stem but twisted at the base to lie in two horizontal ranks, 1-2 cm long and 1-2 mm broad; unlike most other species in the family Cupressaceae, it is deciduous, losing the leaves in the winter months, hence the name 'bald'. It is monoecious. Male and female strobili mature in about 12 months; they are produced from buds formed in the late fall, with pollination in early winter. The seed cones are green maturing gray-brown, globular, 2-3.5 cm in diameter. They have from 20–30 spirally arranged four-sided scales, each bearing one or two (rarely three) trianglular seeds. The number of seeds per cone ranges from 20–40. The cones disintegrate when mature to release the large seeds. The seeds are 5-10 mm long, the largest of any species in the cypress family, and are produced every year but with heavy crops every three to five years. The seedlings have 3–9 (most often 6) cotyledons.

The largest individual specimen is "The Senator", near Longwood, Florida; it is 35 m tall, and with a trunk diameter of 344 cm and an estimated volume of 119.4 m³. While the tallest known, near Williamsburg, Virginia, is 44 m tall, and the stoutest known, on Cat Island, Louisiana, is 521 cm diameter.

Taxonomy

The closely related Taxodium ascendens (Pondcypress) is treated by some botanists as a distinct species, while others classify it as merely a variety of Baldcypress, as Taxodium distichum var. imbricatum (Nutt.) Croom. It differs in shorter leaves borne on erect shoots, and in ecology, being largely confined to low nutrient blackwater habitats. A few authors also treat Taxodium mucronatum as a variety of Baldcypress, as T. distichum var. mexicanum Gordon, thereby considering the genus as comprising only one species.

Habitat

Range

The native range extends from Delaware Bay south to Florida and west to Texas and southeastern Oklahoma-(Little Dixie region, Oklahoma), and also inland up the Mississippi and Ohio Rivers north to southern Illinois and Indiana. Ancient Baldcypress forests, with some trees more than 1,200 years old, once dominated swamps in the southeast US. The largest remaining old-growth stand of Baldcypress is at Corkscrew Swamp Sanctuary, near Naples, Florida. These trees are around 500 years of age and some exceed 40 m in height.

It is native to humid climates where precipitation ranges from about 760 mm (in Texas) to 1630 mm (along the Gulf Coast).

Although it grows best in warm climates, the natural northern limit of the species is not due to a lack of cold tolerance, but to specific reproductive requirements; further north, regeneration is prevented by ice damage to seedlings. Larger trees are able to tolerate much lower temperatures and lower humidities.

Soils and Topography

Most Baldcypress grow on flat ground on alluvial soils, usually at elevations of less than 50 m above sea level, although some stands may occur at elevations of 500 m in Texas.

Baldcypress occurs mainly along riparian (riverside) wetlands normally subject to periodic flooding by silt-rich 'brownwater' rivers, unlike the related Taxodium ascendens, which occurs in silt-poor blackwater rivers and ponds. Baldcypress tolerates minor salinity, but does not grow in brackish or saline coastal waters.

Ecology

The seeds remain viable for less than one year, and are dispersed in two ways. One is by water; the seeds float and move on water until flooding recedes or the cone is deposited on shore. The second is by wildlife; squirrels eat seeds but often drop some scales from the cones they harvest. Seeds do not germinate under water and rarely germinate on well drained soils; seedlings normally become established on soil that is continuously saturated, but not flooded, for one to three months. After germination, seedlings must grow quickly to escape floodwaters; they often reach a height of 20–75 cm (up to 100 cm in fertilized nursery conditions) in their first year. Seedlings die if inundated for more than about two to four weeks. Natural regeneration is therefore prevented on sites that are always flooded during the growing season. Although vigorous saplings and stump sprouts can produce viable seed, most specimens do not produce seed until they are about 30 years old. In good conditions, Baldcypress grows fairly fast when young, then more slowly with age. Trees have been measured to reach 3 m in five years, 21 m tall in 41 years, and 36 m in 96 years; height growth has largely ceased by the time the trees are 200 years old. Some individuals can live over 1,000 years. It may be difficult to determine the age of an old tree because of frequent missing or false rings of stemwood caused by variable and stressful growing environments.

Baldcypress growing in swamps have a peculiarity of growth called cypress knees. These are woody projections sent above the ground or water that are part of the root system. Their function was once thought to be to provide oxygen to the roots, which grow in the low dissolved oxygen (DO) waters typical of a swamp (as in mangroves). However, there is little evidence for this; in fact, roots of swamp-dwelling specimens whose knees are removed do not decrease in oxygen content and the trees continue to thrive. Another more likely function is that of structural support and stabilization. Baldcypress growing on flood-prone sites tend to form buttressed bases, but trees grown on drier sites may lack this feature. Buttressed bases and a strong, intertwined root system allows them to resist very strong winds; even hurricanes rarely overturn them.

Many agents damage Baldcypress trees. The main lethal damaging agent is the fungus Stereum taxodi, which causes a brown pocket rot known as "pecky cypress". It attacks the heartwood of living trees, usually from the crown down to the roots. A few other fungi attack the sapwood and the heartwood of the tree, but they do not usually cause serious damage. Insects like the cypress flea beetle and the baldcypress leafroller (Archips goyerana) (closely related to the fruit tree leafroller) can seriously damage Baldcypress trees by destroying leaves, cones or the bark of tree. Coypu also clip and unroot young Baldcypress seedlings, sometimes killing a whole plantation in a short amount of time.

Cultivation and uses

It is a very popular ornamental tree, grown for its light, feathery foliage and orange-brown fall color. In cultivation it thrives on a wide range of soils including well-drained sites where it would not grow naturally due to the inability of the young seedlings to compete with other vegetation. Cultivation is successful far to the north of its native range, north to southern Canada. It is also commonly planted in Europe, Asia and elsewhere with temperate to subtropical climates. It does however require continental climates with hot summers for good growth; when planted in areas with cool summer oceanic climates, growth is healthy but very slow (some in northeastern England have only reached 4–5 m tall in about 50 years), and cones are not produced.

Baldcypress has been noted for its high merchantable yields. In virgin stands, yields from 112 to 196 m³/ha were common, and some stands might have exceeded 1000 m³/ha. Baldcypress swamps are some of the world's most productive ecosystems.

Baldcypress wood has long been valued for its water resistance thus called 'wood eternal'. Still-usable prehistoric wood is often found in swamps in New Jersey and occasionally as far north as New England although it is more common in the southeast. The somewhat-mineralized wood is mined from some swamps in the southeast, and is highly prized for specialty uses such as wood carvings. Pecky cypress, caused by the fungus Stereum taxodii is used for decorative wall paneling.

The Baldcypress was designated the official state tree of Louisiana in 1963, and is considered by some to be a symbol of the southern swamps.

References and external links

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