J Integr Plant Biol. ›› 1974, Vol. 16 ›› Issue (3): -.

• Research Articles •    

The Vegetation of the Hsi-Sha Islands

Chang Hung-ta   

Abstract: The Hsi-Sha Islands is situated in the South China Sea between latitudes 15º30′ and 17º30′N, longitudes 111º and 113º E. As well as the Tong-Sha, Chung-Sha and Nan-Sha Islands, Hsi-Sha Islands is Chinese territory since ancient times. The group of Hsi-Sha Islands consists of more than twenty islands, lagoons, atolls and reefs composed entirely of coral deposits. Geologically, during the beginning of Quaternary the coral reefs (appeared) in the shallow bottom of the South China Sea, subsequently, the sea bottom subsided down gradually, and the reefs uplifted year by year on opposite direction. At present, the islands rise more than one thousand metres from the bottom of the deep water, and extend no less than 10 metres above the sea. Overlying the calcareous rock are the guano deposits, it covers nearly the whole area of the islands and forms a bed of 1–2 metres thickness. The Flora is represented by comparatively few species, so far as we know, no more than sixty species are existing on the islands, all of them seem to have been immigrants by various ways from the neighboring continents and islands, particularly Hainan, with only one exception, i.e. Pisonia grandis, the plants collected on the His-Sha Islands are the same as those reported for Hainan, some of them, such as Scaevola hainanensis, Bidens biternata and Angiopteris fukiensis, are endemics of Hainan flora, although no real endemics are to be found on the coral islands. The remarkable characteristics of the vegetation tends to be xerophytic. The characteristics occur in two forms, one in the succulent feature of the herbs and shrubs, the other in the indumentum of the stems and leaves. A similar feature is to be found on the arborescent species, although Pisonia grandis grows to a height over 10 metres with a trunk of 60 cm in diameter, the tree is weekly lignified, a lot of water-storage tissues composed of parenchymatous cells replaced the fibrous cells and vessels in the xylem. The plant communities are in the condition of different stages of succession. Three serel communities are recognized: Mobile dune community occurs along the sea shore. It is characterized by the halophytic habit. The runners are peculiarly well fitted to act as a pioneer in stabilizing the sandy shore. Coast scrub community lies in the inner part of the mobile dune community, and stands along the rims of the islands. It is characterized by the drier habitat, and most of the shrubs and herbs are xerophytic in habit. Forest community is situated in higher stage of the succession. It is constituted by a single dominant, Pisonia grandis, and occurs over the central part of the islands, and the trees are growing upon the guano deposits. Since typhoon in frequent, the forest is suffered heavy destruction repeatedly, in certain locality, it would bring about regressive succession.

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