Ryukyu Broadleaved Evergreen Forest

On Okinawa much of the natural forest has been badly disturbed, but there are still good stands on some islands, for example, on Iriomote. Here the dominant tree species are Castanopsis sieboldii, Distylium racemosum, Michelia compressa var. formosana and Quercus miyagii, beneath which is a diverse shrub layer of species like Ardisia sieboldii, Daphniphyllum teijsmannii, Lasianthus cyanocarpus, Psychotria rubra, Randia canthioides and Sysygium buxifolium. The tree fern flora is very diverse with species such as Alsophila pustulosa, Cyathea fauriei, Gymnosphaera denticulata and G. podophylla. There are also many lianas including Epipremnum mirabilis, Flagellaria indica, Freycinetia formosana, Smilax china var. kuri and epiphytes such as Gastrochilus japonicus,  Neottopteris australasica and Psilotum nudum. Other ferns include Abacopteris triphylla, Bolbitis koidzumii, Colysis pothifolia, Diplazium virescens, Lindsaea chienii, Rumohra aristata and Tectaria phaeocaulis.

Ryukyuan Pine Forest

The BioProvince’s main pine species is the endemic Pinus luchuensis (Pinaceae) and ranges from Akuseki in the north, through the Amami Islands, Okinawa and to Iriomote in the south. It tends to occur in disturbed areas.

Ryukyuan Mangrove

Mangrove forests are well developed in the estuaries and lagoons of Iriomote and typically include Avicennia officinalis, Bruguiera conjugata, Kandelia candel, Lumnitzera racemosa, Rhizophora mucronata and Sonnerataia alba.

Ryukyuan Strand Communities

On raised coral reefs the main species include Limonium wrighteii on the seaward fringes followed by Crossostephium chinense, Hedyoyis biflora var. parvifolia, Osteomeles subrotunda, Zoysia tenuifolia, and the endemic Aster miyagii (Asteraceae) in the more inland zones. The sandy shores include Glehania littoralis and Ixeris repens in the pioneer zone, with Cassytha filiformis, Ipmoea pescaprae subsp. brasilense, Spinifex littoreus, Thuarea involuta and Vitex rotundifolia in the more stable inland areas.

Ryukyuan Beach and Dune Vegetation

In addition to the beach vegetation three sand dune vegetation zones have been recognised in the Ryukyu Archipelago.

Beach Vegetation
The sandy shores include Glehania littoralis and Ixeris repens in the pioneer zone, with Cassytha filiformis, Ipmoea pes-caprae ssp. brasilense, Spinifex littoreus, Thuarea involuta and Vitex rotundifolia in the more stable zones.

Vigna marina- Ipomoea pes-caprae Pioneer Zone
Mainly confined to the higher parts of the beach this vegetation zone is often reached by the sea and during typhoons maybe completely washed away. Other species may include Calystegia soldanella, Glehnia littoralis, Panicum repens, Raphanus sativus var. hortensis, Spinifex littoralis and Thuarea involuta.

Zoysia sinica Pioneer Zone
This vegetation usually occurs in areas where the Ipomoea pes-caprae community has been disturbed. It includes most of the species mentioned for the Vigna marina- Ipomoea pes-caprae zone. Other associated species include Artemisia capillaries, Cirsium spinosum and Wedelia prostrate.

Glehnia littoralis-Spinifex littoralis Fixed Dune Zone
This vegetation develops on stabilised sand where some humus has accumulated. The physiognomy is mainly determined by the stiff grass Spinifex littoralis which can reach heights of 70 cm. Most of the species mentioned for the Vigna marina- Ipomoea pes-caprae and Zoysia sinica pioneer zones can also be found here. Others include Clerodendrum inerme, Lepturus repens and Maytenus diversifolius.

References

Hosokawa, T., Tagawa, H. & Chapman, V. J. 1977. Mangals of Micronesia, Taiwan, Japan, the Philippines and Oceania. In: Ecosystems of the World 1 - Wet Coastal Ecosystems. Ed. V. J. Chapman. Elsevier Scientific Publishing Company.

Miyawaki, A. & Suzuki, K. 1993. Dry Costal Ecosystems of Japan. In: Ecosystems of the World. 2B. Dry Coastal Ecosystems. Africa, America, and Oceana. Ed. Eddy van der Maarel. Elsevier.

Numata, M. (ed). 1974. The flora and vegetation of Japan. Elsevier Scientific Publishing Company.

Numata, M., Miyawaki, A. & Itow,  D. 1972. Natural and semi-natural vegetation in Japan. Blumea, 20: 435-481.