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Endangered Plant: Gleditsia vestita of Hunan, China

Volume 3 Number 10 - February 2003
Anon.

Gleditsia vestita Chun & How ex B.G.Li is reduced to two individuals in the wild on the slopes of Mt Hengshan, Hunan Province (Figure 1). No young trees have been seen under the canopy. It is critically endangered and has national protection (Li-kuo, F. and Jian-ming, J. (eds) 1992. China Plant Red Data Book. Science Press, Beijing. National Environment Protection Bureau. 1987. The list of rare and endangered plants protected in China. Botanical Institute of Chinese Academy of Sciences, Academy Press, Beijing).

One of the trees is thought to be 270 years old. It is 8 m high, with a trunk diameter of 80 cm (chest height), a canopy of 4 x 5 m2 and a growing head, but the trunk is rotten and hollow. The other tree is more than 90 years old, 13 m high with a diameter of 30 cm (chest-height), it has a straight trunk, flowers and bears fruit. When this species was first found in 1954 there were five plants. Only one of the trees produces seed and human activity frequently destroy the balance of the forest’s ecological system; therefore the species is faced with becoming extinct in the wild.

This tree is widely planted for ornamental shade and hedge purposes in mountain areas, hills and flatlands of the sub tropics of China because it is easy to transplant and grows under a wide variety of conditions. The bright brown or reddish heartwood, with its thin layers of pale yellow sapwood is hard, strong and coarse-grained. It takes a high polish and is durable in contact with the soil. Its lumber is used for rough construction, furniture, interior finish and turnery.

To save this species, Guo Cheng-ze, the Director of Nanyue Arboretum has taken more than ten forestry experts to study the plant in the wild over the last 24 years. Research has included botanic and ecological characteristics, distribution, cause of reduction and the development of techniques for propagation and cultivation through seed, cuttings and grafting.

More than 2200 saplings have been grown. 500 trees of G. vestita have been planted in a taxonomic and rare and endangered plant plot in the garden in an area of about 2 km2. All the trees have survived. They have a mean height of 8 m with a trunk diameter 18 cm (chest-height),the tallest is 12 m with a trunk diameter of 24 cm (chest-height), They have flowered and fruited; the seeds are used for propagation.

Botanic Characteristics

It is a deciduous, broadleaved tree, 8-13 m high with a trunk diameter of 30-80 cm (chest-height), the bark is brown with scattered grey white stoma, and regular pinnate leaves, clustered on short branches; 10-18 pairs pinnae, ovate, oblong-ovate or elliptic-ovate 2-6.5 x 1.5-2.5 cm, apex obtuse or round-obtuse and a little pointed, the base wide cuneate or near round, pilose, it has three types of flower: hermaphrodite, unisexual or a hybrid, corolla white, calyx lobes 4, stamens 8-10 and gynoecium with undeveloped stamen, linear ovary; pod squat-shaped long strip with irregular winding, 15-42 x 2.5-4.2 cm wide, dense golden hairs (this is a conspicuous character and easily distinguished). Flowering-time May-June, fruiting November. It is also known as Chinense villus honeylocust, Chinense villus fruit honeylocust or Chinense golden villus honeylocust.
 

Ecological Characteristics

The natural habitat is on the north-east slope of Mt Hengshan’s main peak at longitude 112o45’E and latitude 27o12’N, at an altitude of 750 m. This area is managed by the secondary work area of Nanyue forest farm near Guangji temple.

The soil of the site is derived from weathered granite, yellowish-brown mountain loam with a pH 5.5 – 6.5; the soil layer is deep, loose, moist, rich in nutrients and well-drained. The climate is mid subtropical with moist mountainous monsoons, the annual mean temperature is 13oC, minimum temperature of -7.4oC, maximum temperature of 31.4oC; frost free period 227 days, ice period 30 days; the annual rainfall is around 1600-2500 mm; the annual cloudy period is 224 days, the relative humidity is between 65%-85%.

It occurs in a forest plant community, 13.3 km2, with evergreen and deciduous broad-leaved trees, the major species are Castanopsis eyrei, Cyclobalanopsis multinervis, and Sycopsis sinensis. There are over 100 trees of Magnoliaceae, Juglandaceae, Betulaceae, Ulmaceae, Staphyleaceae, Theaceae and Ericaceae etc.

According to observations the species is a hardy, drought-enduring plant which is best planted on rich, deep, moist and loose loam.
 

Experimental Plot of the Arboretum

The experimental plot of the Arboretum is situated on the south-east slope of Mt Hengshan’s main peak at an altitude of 400 m, the distance between both sides is 8 km. The soil here is red-yellow mountain loam with a pH 5 – 5.5, and deeper, loose, moist, fertile, well-drained soil. The annual mean temperature is 16oC, minimum temperature -8oC, maximum temperature 40oC, frost-free period is 300 days, the annual mean rainfall 1400-1700 mm with a relative humidity of 60%-80%. The trees are mainly middle-aged, needle-leaved species such as Pinus massoniana and Loropetalum chinense, Rhododendron simsi, Eleagnus pungens and Lespedeza davidii. Although the ecological environmental conditions are different, the species have grown well in the experimental plot.
 

Propagation Techniques

Seed collection and germination

The pods are picked up from the fruiting tree and put in the sun for several days. When the pods dehisce, selected seeds were stored dry or in layers of moist sand over the winter. 1000 seeds weigh 196 g. At room temperature germination rate is 20% and at a constant germination temperature the germination rate rises to 100%, but if the temperature is changed the rate is reduced to 14%.

Three methods of propagating saplings

Seed: Sow seeds in spring, from the middle ten days of February to March, drilling with spacing of 25 cm, depth is 2 cm, each drill sowing 50-60 grains, covered with two layers (1 cm of soil and a layer of rice straw so the soil is not visible). Seeds must be sterilised in potassium permanganate fluid and soaked for 20 minutes. Germination takes place after about 30 days. When one third has germinated, lightly take off the rice-straw, and spray immediately with 0.5% potassium permanganate fluid to prevent disease, and 2-3 more times at intervals of 7 days for good nursery management. 95% of the seedlings survived. In the first year the seedling mean height is 0.7 cm, the largest is 0.92 cm. The leaves fall off the seedlings in the last ten days of October and sprout in March the following year, which is a good time for planting.
Cuttings: Six cutting trials from 1982-1991 were undertaken, from which of the 8% raised, 40% survived. Half-woody young branches were used for cuttings, 10-15 cm long. The best method in which the cuttings were stored in a chaff ash bed in the summer survived at a rate of 30% to 40%.
Grafting: Cut or cleft-grafting and layering of a half-woody cutting was undertaken in spring. The stocks used were Gleditsia sinensis, G. delavayi and G. triacansae; the scions taken were one year old from the canopy of the wild seed tree. In total 1018 plants were grafted and 901 plants survived (88%).

Guo Cheng-ze, Guo Da-zhu and Ma Pei-zhen
Nanyue Arboretum
Nanyue Jingsha Road No. 26, 3-201
Hengyang
Hunan Province
People’s Republic of China



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