Xanthocyparis vietnamensis

Xanthocyparis vietnamensis

Xanthocyparis vietnamensis is a plant belonging to the family of the cypress family ( Cupressaceae ). It was discovered in Vietnam in 1999. It is characterized by the simultaneous occurrence of juvenile and adult leaves on the same branch. The scientific name means "Vietnamese Goldzypresse " and refers to the home of the type and the color of the wood.

• 6.1 Notes and references

Features

Appearance and a hard place

Xanthocyparis vietnamensis is achieved a small to medium sized tree, the stature heights of 10 to 15 meters. The trunk is monopodial, turning round and has a diameter of up to 50 centimeters. The bark is smooth on branches and thin, purplish to reddish brown and peels off in thin flakes and stripes. At the base of larger trees the bark is soft and fibrous, brown to gray- brown and peels off in numerous thin strips. The branches are long and more or less horizontal from. There are numerous leafy branches that are horizontal, overlapping layers or slightly hanging down. They form a pyramidal crown that is spreading and irregular in older trees with young trees.

The leaves of adult trees are mainly the adult forms, but there are also young people on adult trees leaves and transitional forms.

The youth leaves are needle -shaped and available in four - whorls on the branches, the same polymorphic, the free, distal part is now at an angle of 90 ° from the axis and is 15 to 20 millimeters long, 1.5 to 2 millimeters wide. The proximal, running down on the axle part is around 4 to 5 millimeters long. The leaves are linear, entire, tapering to a fine point. The stomata are located in two whitish bands on the underside of leaves. In these frequency bands to form six to seven irregular rows parallel to blade axis. Transition leaves already resemble the adult leaves, but are 5 to 7 millimeters longer, lanceolate and are available at a 45 ° angle from. The adult leaves are scale-like. You are decussate, short run down to the axle and arranged dachziegelig. On the last and penultimate side branches are 1.5 to 3 mm long and 1 to 1.3 millimeters wide. The side sheets are slightly longer than the other. The latter are narrow oval - rhombic, keeled, pressed, its edge is denticulate to entire, pointed to the pointed end. Wherein the side blades of the proximal portion is reduced continuously, the distal portion is at an angle of 30 ° free from the axis is straight to a sickle shape. The leaf margin is denticulate, margin entire to the pointed to sharp end. The stomata of the adult leaves are inconspicuous, predominantly covered on the upper leaf surface and a layer of wax. Glands are inconspicuous and are predominate in depressions below the keeled distal part of the leaves.

Cones and seeds

The male, pollen- forming cones are 2.5 to 3.5 × 2 to 2.5 millimeters in size, oval to round, have 10 to 12 Mikrosporophylle of approximately 1 x 1 mm size. Their edge is denticulate, the tip is mucronate. They are green and later yellow- brown. Each microsporophyll carrying two large, round, yellow microsporangia. The pollen is spherical.

The female cones are individually rare in twos or threes on the outer edge, or near the base of the occupied with adult leaves branches. The cones require two years to mature. They are green at first, later they become dark brown to dull. They are nearly spherical and open 9 to 11 × 10 to 12 millimeters in size. Some remaining after seed shedding on the plant. The bract - scale complexes are available in two, rarely three decussate pairs. Rarely there are irregular or reduced neck. The complexes are fold - up nearly peltate. The lower pair is elongated, while the distal end at the widest, the outer edge is rounded, but irregular. The outer surface is initially smooth, later is furrowed wrinkled or radial. The furrows are based on a clear, 1 to 2.5 mm long umbo. The inner surface of the complex is red-brown, the seeds scars are white or gray. Each fertile bract has one to three ovules, with six leaves per pin, the top two are sterile. There ripe maximum of eight to nine seeds per cone.

The seeds are oval or irregularly shaped, flattened, and 4.5 to 6 × 4 to 5 millimeters long and 1.5 to 2 millimeters thick, there are two lateral wings included. The seed is light brown to reddish brown, at the base has a white hilum, at the top of Mikropylen - beak is often obtained. The seed wings are 0.5 to 1 mm wide, thin, membranous and brighter than the seeds.

Dissemination and locations

Xanthocyparis vietnamensis comes very locally in northern Vietnam in the province of Hà Giang ago. Here in the Bat Dai Son Mountains near the Chinese border, it thrives at altitudes from 1060 to 1180 meters.

It grows in mixed deciduous - conifer forests fog. On conifers come Amentotaxus Argotaenia, Nageia wallichiana, Pseudotsuga sinensis, Podocarpus and Taxus chinensis pilgeri ago. The dominant deciduous trees are species of the genera Acer, Carpinus, Lithocarpus, Quercus and Ulmus, and often there is Pistacia weinmannifolia and Platycarya strobilacea. In the second tree layer particularly Elaeocarpus, Eriobotrya, Sorbus and Schefflera are encountered. The shrub and herb layer is very rich in species, in the latter orchids are very common, as well as ferns and mosses.

The limestone ridge on which Xanthocyparis vietnamensis grows, are heavily eroded. Between marble -like, weathering resistant rocks are small erdgefüllte bags. The climate is subtropical, and during most of the year moist to wet. The annual average temperature varies between 14 and 18 ° C, annual rainfall is 2000-2400 mm.

Use

The wood is very hard, yellow- brown and fragrant. It is of high quality, but is used only locally due to lack of transport.

Endangering

Xanthocyparis vietnamensis was classified as critically endangered shortly after the discovery, this has not changed even after the discovery of new populations. The area of ​​the species was initially estimated at less than 10 km ², it was known in 2004 only about 560 individuals. 2006 there were almost 15 km ² and about 600 individuals. Risk is represented mainly by the logging. Clearing for agriculture is no danger, as the steep mountain ridges, on which the species grows, are not suitable for agriculture.

History

The species was discovered in 1999 and first described invalid as a new species of the genus Thuja. In 2002 she was first described as a new species and genus Xanthocyparis vietnamensis.

Documents

• A. Farjon, Nguyen Tien Hiep, DK Harder, Phan Ke Loc, L. Averyanov: A New Genus and Species in Cupressaceae ( Coniferales ) from Northern Vietnam, Xanthocyparis vietnamensis. Novon, Volume 12, 2002, pp. 179-189.