(15) 土沉香 (牙香樹、白香木)
Aquilaria sinensis (Lour.) Gilg.
瑞香科 (Thymelaeaceae)

英文名 (English name): Incense Tree

中國境內現狀:近危 (NT)。國家二級保護野生植物。已載入《中國植物紅皮書》和《廣東省珍稀瀕危植物圖譜》。
Status in China: This plant is near threatened (NT) In China, and all efforts to preserve this wonderful specimen should be executed immediately to keep the species alive. Logging & deforestry are a core cause of it’s status.

形態特徵:常綠喬木;幼枝疏被柔毛。葉互生,革質,倒卵形至橢圓形,長5-11厘米,寬2-4厘米,全緣。花黃綠色,芳香,排成頂生或腋生的傘形花序;花萼5裂,兩面均有短柔毛;花瓣10,鱗片狀;雄蕊10;子房2室,被短柔毛。蒴果木質,倒卵形,長2.5-3厘米,直徑約2厘米。
地理分布:香港各地。海南、廣東、廣西、雲南各地。
生境與生態:生於低地常綠闊葉林及風水林中。花期:4月;果期:7月。

本種是中國特有的珍貴藥用植物,樹幹受真菌侵入後產生的樹脂為中藥“土沉香”,供香料及藥用。葉濃綠,樹冠緊密,可用作庭園樹。潛在的威脅因素包括生境破壞及非法採伐,但本種在香港常見,很多生長地點在郊野公園內,也未受任何特別威脅。香港及華南地區已開始人工繁殖,用作綠化樹種。

Description: The aquilaria sinensis is an evergreen tree, when the tree is young, the branches are sparse. It’s leaves are leathery and obovate (which means that they are narrower at the base of the leaf than in the center),

Leaf Size: Typically 5-11 cm long and 2-4 cm wide depending on how old the specimen is, apex short acuminate, base broadly cuneate, margin entire, glabrous.

It’s Flowers are a beautiful yellow-green.

Found in multiple places Hong Kong, Hainan, Guangdong, Guangxi and S Yunnan provinces.

This is a delicate and sought after plant, known for its medicinal properties and wonderful fragrance. The wood is called “Chen Xiang” and people typically use it for medicinal reasons, or for a great ornament!

Although it is very common in Hong Kong, this plant’s potential threats are mainly destruction of habitat and over-consumption. A large quantity of these plants are under the protection of country parks.

 

Conservation status

    The species is chiefly distributed in South China including Hong Kong. However, owing to the intensive use of the species, wild populations outside Hong Kong have become rare and large Agarwood trees are also uncommon. The 2000 IUCN Red List of Threatened Plants published by The World Conservation Union (IUCN) listed the threat status of Aquilaria sinensis as vulnerable. Regarding its conservation status, the plant is considered “an important source of medicine” and is “restricted to Jinghong in Yunnan, Guangdong including Hainan Island and Guangxi” (i.e. endemic to China). It is “mainly found in semi-evergreen monsoon forest up to altitudes of 400 m”. There is concern over the rates of exploitation and the damage to trees incurred during the harvesting of the medicinal balm. Habitat loss and clearance are also frequent (Oldfield et al., 1998). Aquilaria species are also regulated under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).

Status in Hong Kong

As mentioned above, the species is common in lowland areas in Hong Kong, particularly in fung shui woods behind rural villages. The species has also been found in Country Parks. It is known that the species was once wildly cultivated in South China and Hong Kong for the production of incense sticks, although no large scale plantation is known nowadays in Hong Kong. This may explain why the species is abundant around villages in modern times. Regardless of the long history of cultivation in Hong Kong, the local populations are well within its range of distribution where it regenerates in wild with vigour, and the species is therefore considered a native plant of Hong Kong (Iu, 1983)

 

In mainland China, the species is listed as a category II protected plant in the “List of Wild Plants under State Protection” (1999), part of the Chinese legislation promulgated by the State Council. It is considered vulnerable in the China Plant Red Data Book, as it has become depleted due to severe damage of trees caused by indiscriminate collection of the balm used in Chinese medicine (China National Environmental Protection Agency & Institute of Botany, Chinese Academy of Sciences, 1992).A recent book, Rare and Endangered Plants in Guangdong Province (South China Institute of Botany & Wild Animal and Plants Protection Office of Guangdong Province, 2003) reported that in Guangdong province over-exploitation and over-cutting of numerous large trees of the species have made it rare and threatened. Due to its conservation status in Mainland China, the species is also considered precious in Hong Kong, and it has been included in the book Rare and Precious Plants of Hong Kong (South China Institute of Botany & AFCD, 2003).
Exploitation of this plant species for agarwood has been rare in Hong Kong, but there are recent reports that the species has been illegally exploited in our countryside. Although these incidents have not caused serious threat to the overall survival of local Aquilaria populations, the trunks of the affected trees are being cut or felled for extraction of agarwood for its oil, chips, and incense used for aromatherapy, to an extent that the trees may not be able to recover (Figures 5 & 6) .Under the Forest and Countryside Ordinance (Cap. 96), all plants within forests and plantations on Government land are under protection. The maximum penalties for contravening the Ordinance are $25,000 fine and one year imprisonment.

Conclusion

From the point of view of flora conservation in Hong Kong, and because in other parts of China the species is over-exploited and depleted, the local populations of Aquilaria sinensis represent some of the best remaining healthy populations in China. The plant communities to which local populations of Aquilaria sinensis belong (lowland broadleaved forests and fung shui woods) have been well-preserved by both former villagers and local legislation, including the Country Parks Ordinance (Cap. 208) and Forests and Countryside Ordinance (Cap. 96). Most illegal exploitation of the species occurred recently involve unsustainable harvesting, which has caused undesirable impacts to the local populations of Aquilaria sinensis. These incidents show that the conservation of this nationally rare and endangered species deserves attention.

References

  • China National Environmental Protection Agency & Institute of Botany, Chinese Academy of Sciences, 1992. China Plant Red Data Book — Rare and Endangered Plants 《中國植物紅皮書–珍稀瀕危植物》. Science Press, Beijing.
  • Iu, K. C. 1983. The Cultivation of the “Incense Tree” (Aquilaria sinensis). Journal of the Hong Kong Branch of The Royal Asiatic Society 23: 247-249.
  • IUCN. 2000. IUCN Red List of Threatened Plants (available online at http://www.redlist.org).
  • Oldfield, S., C. Lusty & A. MacKinven. 1998. The World List of Threatened Trees. World Conservation Press, Cambridge, U.K.
  • South China Institute of Botany & Agriculture, Fisheries and Conservation Department. 2003. Rare and Precious Plants of Hong Kong 《香港稀有及珍貴植物》. AFCD, Hong Kong.
  • South China Institute of Botany & Wild Animal and Plants Protection Office of Guangdong Province, 2003. Rare and Endangered Plants in Guangdong Province 《廣東珍稀瀕危植物》. Science Press, Beijing.