Economic forest trees
Economic forest are those where the main management emphasis is on forest products rather than timber, such as fruit, bark, leaves, tree sap, branches, flower buds and tender sprouts.
China is rich in economic forest tree species. Over 1,000 economic tree species have been discovered, including 300 with oil contents greater than 20%, and more than 90 with starch contents greater than 20%. Of these, about 100 species have been cultivated on a production scale, and others are expected to be exploited and utilized. Here, only the main species, which are rich in germplasm resources, have a long cultivation history and grown on a large scale and over a wide area, are described briefly below.
A. Edible starch tree species (dry fruit species)
The main species are jujube, chestnut, persimmon and ginkgo.
Jujube (Ziziphus spp.)
Jujube is a special dry fruit tree species, native to China, and this rich resource consists of 18 species (including four introduced from abroad in Taiwan Province). In addition to such species as the Sour (Z. jujuba var. spinosa), Chinese (Z. jujuba), Indian (Z. mauritiana), Sichuan (Z. xiangchengensis) Grand Frui (Z. mairei) and Mountain jujube (Z. montana), there are many varieties and subspecies. The more important varieties are the Spineless (Z, jujuba var. inermis; also known as Red jujube, Chinese date tree or Grand jujube), Zigzag (Z. Jujuba var. tortusa; also known as Twin Dragon Paw jujube or Dragon Feelers jujube), Calabash (Z. Jujube var. lageniformis; also known as Strangled stem or Mopan jujube) and the Calyx-remained jujube (Z. Jujuba cv. carnosicalleis).
The diverse range of cultivated jujubes can be divided into 2 eco-forms: Southern and northern jujube. Seven hundred such cultivars have been recorded.
Sour jujube is the original species. It is widely distributed and has many diverse types. Although collection has been carried out in only a part of its total production area, more than 150 types have been recorded, providing a valuable gene resource for breeding.
Chinese chestnut (Castanea mollissima)
Chinese chestnut is considered to be the best quality edible chestnut in the world for its excellent taste and fragrance. It originated in China, has a history of over 2,000 years of cultivation, and is widely distributed over a wide area. Its existing local cultivars are commonly divided into 5 populations, i. e., Northern, Yangtze River Valley, Sichuan and Guizhou, Southern and Southwestern. Additionally, the Dandong chestnut, which belongs to the Japanese chestnut (Castanea crenata) system, is planted as a major cultivar in Liaoning Province. In China there are about 300 chestnut cultivars.
Ginkgo (Ginkgo biloba)
Ginkgo, also known as White Fruit, is an ancient plant species remaining only in China as a í░living fossilí▒. It is an elegant ornamental tree and important dry fruit and medicinal plant.
Ginkgo has been cultivated as an important dry fruit tree for about 1,000 years, and over 180 trees more than 500-years-old have been found in China. At present Ginkgo is cultivated in 20 provinces and regions across China, with a yearly fruit production of over 7,000 t.
Ginkgo has 3 varieties: 1, Plum pit (G. biloba var. typica); 2, Buddhaí»s-hand (G. biloba var. huna) and 3, Horse bell ginkgo (G. biloba var. apiculata). There are, moreover, many cultivars and local varieties.
B. Tea trees
Tea, as a drink, originated in China, The history of tea cultivation, processing and drinking dates back to 1,000 BC. The diversity of tea genetic resource in China is the greatest in the world. There are 12 species and 6 varieties in the genus Camellia, Section Thea, including 3 cultivars: Puí»er (Camellia sinensis var. assamica), Dehong (C. sinensis var. dehungensis) and White Downy tea (C. sinensis var. pubilimba).
Tea is distributed widely in China. It is planted in over 1,000 counties, 18 provinces and regions and occupies 27% of farmland.
Tea trees of various types are grown from several meters to 2,600m above sea level. More than 200 places have been recorded as having large tea trees with a diameter of over 50cm. In recent years, a number of very-large tea trees with a diameter of over 1m, and wild tea stands have been discovered in southern and southwestern parts of Yunnan Province.
Each province has a number of elite tea cultivars. Fifty-two national elite cultivars which have been examined and approved by the Chinese Government are divided into 2 groups. The first group includes sexually propagated traditional local cultivars, such as Mengku Grand Leaf, Lingyun White Downy, Early White, Yuntaishan and Yichang Grand Leaf teas, The second group contains clones selected from single tea plants, such as Hairy Crab, Teiguanyin, Yunhang No. 10, Xiangnong No. 12 and Longjing No. 43 teas.
C. Oil tree species
There are more than 400 woody plant species used for oil production in China, and are cultivated in over 6 million ha. More than ten tree species (including some dry fruit species that contain oil) are cultivated for edible oil. The main species are Oil camellia (Camellia spp.) and common walnut (Juglans spp.). Those cultivated for industrial oil are mainly the Tung oil tree and Chinese tallow tree.
Oil camellia is an important edible oil tree species unique to China. China is in the centre of its natural distribution area, covering the southern, middle and northern belts of the subtropical zone.
Oil camellia has a rich germplasm resource and a long history of cultivation. In addition to the Common oil camellia tree (Camllia oleifera), the main cultivars are Microfruit tea-oil (C. micriocarpa), South China tea-oil (C. vietnamensis), Youxian tea-oil (C. yuhsienensis), Zhejiang Red Flower Tea-oil (C. chekiang-oleosa), Guangning Red Flower Fruit tea-oil (C. semiserrata), Tengchong Red Folower tea-oil (C. reticulata), Bobai Giant Fruit tea-oil (C. gigantocarpa), Pear tea-oil (C. octopetala), South White Flower tea-oil (C. semiserrata var. albiflora), Nanrong tea-oil (C. nanyongensis) and Pitar tea-oil tree (C. pitardii), there being 22 in total. In the southern provinces, dozens of genotypes still remain in a wild status, such as the Guifengshan tea-oil, Zhaoping tea-oil and Canwu White Flower tea-oil tree. According to the time of fruit harvesting, the cultivars can be divided into 4 seed groups, i. e., Autumnal Equinox (16th solar term), Cold Dew (17th solar term), Frostí»s Descent (18th solar term) and The Beginning of Winter (19th solar term) seeds.
In addition, six elite families and 39 clones with high yields have been selected from various places.
Common walnut, as an important tree species, which provides both edible oil and dry fruit, has a long history of cultivation and rich germplasm resources in China. It is widely distributed in both South and North China in 20 provinces, cities and regions.
China is one of the centres where walnut originated. In China there are eight walnut species (three of them introduced from other countries), i.e., Common (Juglans regia), Iron (J. sigillata), Manchurian (J. mandshurica), Chinese (J. cathayensis), Ma (J. hopeiensis), Siebold (J. sieboldiana), Heart-shaped (J. cordiformis) and Eastern Blachk walnut (J. nigra).
There are many walnut varieties and types in China. The main types are Spiked, White Water, Super Grand, Red Pulp, Single Leaf and Shell-less walnut.
In China only two species of the genus Juglans have been cultivated for nut produuction, i. e., the Common (J. regia) and Iron walnut (J. sigillata), but many local cultivar types have been derived, According to an incomplete survey, there are over 500 designated genotypes, which have been divided into two populations, i. e., Common and Iron walnut populations. In the first population, there are 51 cultivars and elite clones (29 late ripening and 22 early ripening types), and in the second there are 16 cultivars and elite clones.
Tung oil tree (Vernicia spp.)
The Tung oil tree is an economic species unique to China with a cultivation history of over 1,000 years. Its main product is tung oil, and China is considered to be a major country for its production. The cultivation of tung oil trees occurs in 15 provinces and regions in the south of the Qinling mountains with a total area of 2.07 million ha and an average yearly production of 120,000t.
The Chinese wood-oil tree (Vernicia fordii, also known as the Three-year tung oil tree) and Wood-oil tree (V. montana, also known as Thousand-year tung oil tree) are commonly cultivated in China where both species originated. More complex traits and performance are found in the three-year tung oil tree which has over 100 local cultivars, divided into 5 groups, i.e., Small Rice, Grand Rice, Duinian, Shiping and Chai tung oil tree.
The main cultivars of the Thousand-year tung oil tree are Micro-fruit, Macro-fruit and Rhombus tung oil trees.
D. Tree species for sap and resin
In this group, trees are cultivated mainly for harvesting sap, lacquer, rubber and resin, but only the lacquer tree (Toxicodendron vernicifluum) will be described here.
The lacquer tree is an excellent species for production of natural paint and oil. The lacquer, harvested by cutting bark, is called raw lacquer, or Chinese lacquer, and has a number of unique characteristics, incomparably better than synthetic ones.
The major production areas for raw lacquer are Shaanxi, Guizhou, Sichuan, Yunnan, Hubei and Gansu Provinces with a total land area of 450,000 ha and a yearly production of over 3,000 t.
In China, lacquer trees can be divided into two groups: (1) Grand Wood and (2) Small Wood lacquer tree. There are over 40 local cultivars. Yanggao (also known as Maoba), Zhenxiong, Tianshui and Ziyuan Grand Wood lacquer trees are included in the first group. In the second group there are: Grand Red Robe, Red Bark 8-chi Height, Cupping Jar, Guizhou Red, Yanggao Small Wood, Chongtian Small Wood, Lamp Stand Small Wood, Bamboo Leaf (also known as Chilli Leaf), Small Wood, White Bark Small Wood, Sanbutong, Grand Leaf 8-chi Height and Youyang Small Wood lacquer tree.
E. Silkworm mulberry and host trees
In this group, the host trees for feeding silkworm, lac insect (Laccifer lacca), wax insect (Fricerus pela) and gall makers are included. But only mulberry (Morus) will be described here.
China is the original place for silkworm feeding, mulberry production and silk fabric production and has a long history of 5,000 years. China is ranked first in the world for silkworm cocoon production.
The Yantze River valley is the major area for silkworm and mulberry production, Others are the Pearl River valley and Yellow River valley. Hetian, Kashi and Akesu in the southern part of Xinjiang Uygur Autonomous Region, also have long histories of silkworm and mulberry production. A certain amount of production is also found in Taiwan and Yunnan.
China possesses most species of Morus, with 15 species and 4 varieties. Among them, the Shandong (M. multicaulis), White (M. alba), Guangdong (M. atropurpurea), Mountain (M. bombycis) and Ruisui mulberry (M. mizuho) have been cultivated. Wild species are: the Long Spike (M. wittiorum), Long Fruit (M. laevigata), Black (M. nigra), China (M. cathayana), Small Teeth (M. serrata), Mongolian (M. mongolica), Sichuan (M. notabilis), Tang Ghost (M. nigriformis), Yunnan (M. yunnanensis) and Japanese mulberry (M. australis). The varieties of mulberry are: the Ghost (M. mongolia var. diabolica), Giant Leaf (M. alba var. macrophylla), White Vein (M. alba var. venosa) and Hanging Branch mulbery (M. alba var. pendula).
The species resource appears to be extraordinarily rich in China. At present, about 2,600 samples collected from all over the country have been preserved as a mulberry germplasm resource. The Chinese Academy of Agricultural Sciences has established a mulberry germplasm nursery, the largest of its kind in the world, preserving 1,700 germplasms. The typical varieties of mulberry across China have been divided into eight ecological types: Guangdong mulberry in the Pearl River valley, Lake mulberry in the Taihu valley, Jiading mulberry in the Sichuan basin, Picking mulberry in the middle reaches of the Yangtze River, Shandong mulberry in the lower reaches of the Yellow River, Geru mulberry on the Loess Plateau, White mulberry in Xinjiang and the Liao mulberry in northeastern China.
F. Medicinal trees
China is extraordinarily rich in medicinal plant resource. Of the woody plants, which are of more importance in medicine, 129 species have been recorded. Among them, only Eucommia (Eucommia ulmoides) will be introduced briefly.
Eucommia is a medicinal tree species, unique to China. The medicinal composition of Eucommia contains large amounts of Aucubin (C15H22O9) and pinoresinol diglucoside, and can be used as a diuretic, calmatic and tonic, and for hypertension alleviation and cancer prevention. It is a promising species for further exploitation.
Based on morphological characteristics, Eucommia can be divided into two types: Rough Bark and Smooth Bark. The later is better as it has a thicker and heavier bark for medicine and rubber extraction.
China has established over 799 natural reserves, which play important roles in protecting the valuable and rare economic tree species. A number of important economic forest tree species have been designated as protected plants at the national level and are under special preservation. For example, Eucommia and Ginkgo are in the second class of protected plants at the national level.
The Chinese government has set up corresponding scientific research co-operation groups at the national level for the major economic tree species, such as Jujube, Chinese chestnut, Common walnut and Oil camellia. Based on a general survey, resource nurseries or gene pools have been set up for the main tree species with preliminary success, paving the way for their genetic improvement.
The genetic resources of several economic tree species have, however, been lost, or are under the risk of extinction. For example, in some places, wild tea-oil trees have been felled and there is almost nothing left, or they are dying due to lack of management. A number of valuable mulberry cultivar resources, such as the Sichuan, Long Fruit, Yunnan and Long Spike mulberries are also under threat of extinction, and should be protected immediately. In China, a number of efforts have been made to protect tea tree genetic resources with more than 2,000 samples collected and preserved in Hangzhou National Nursery of Tea Tree Genetic Resources. Some places have taken measures to protect ancient wild tea trees, for example, the Nannuoshan grand tea tree with an age of over 800 years in Xishuangbanna, the Bangwei grand tea tree in Langcan county, Yunnan Province, and the ancient Short-leg Wulong tea orchard in Guilin Village, Jian-ou County, Fujian Province.
Some wild species with a close parentage to cultivars, such as the Sour jujube, Ansu apricot and the wild varieties of Iron walnut and Camellia are often grafted with their cultivars or varieties for profit. This results in a loss of germplasm. The relevant authorities should pay serious attention to this, and take necessary measures to preserve the existing rare germplasm resouces, for example, the wild walnut forest in Yili district, Xinjiang, is the only one in the country, and some special germplasms like the Red Pulp walnut.