The Biodiversity Research On A Tropical Coral Archipelago In The South China Sea

The primary work place of this thesis was in Xisha Archipelago. The Xisha Archipelago is locate in the north of China South Sea, which made up of 34 coral islands and reefs, and its total area was 7.97 km2. The climate of this area belongs to a classic tropical monsoon climate.Xisha Archipelago is the most typical and well-preserved tropical reef ecosystem, and its biodiversity lacks systemic research all through. This research gets the basic data of biodiversity in Xisha Archipelago by a 14 months'continuous observation.The birds in Xisha Archipelago have a number of 33 families and 123 species. In a countinous observation from March 2008 to April 2009, the total number of bird species recorded is 81. There are 4 main sorts of bird which contain about 98% of sum: Passeriformes, Terns, shorebird and Ardeidae. In the sort of Terns, there are 3 species of summer resident bird: Thalasseus bergii, Sterna fuscata and Sterna sumatrana. The other 3 sorts of bird are mainly migration birds. The period which spring migration bird pass Xisha Archipelago is from March to June, mostly concertrated in middle March to middle May; the period which autumn migration birds pass Xisha Archipelago is from September to December, the detailed migration time is different by species. As a result, Xisha Archipelago is an important breeding area for Terns in China, and is also a rest habitat for migration birds in the Asia-Australisia migration way.There would have 5 species of turtle in Xisha Archipelago, but only green turtle and hawksbill were recorded until now, and only green turtle have breeding records. During the period of our research, we recorded 23 times landing of green turtle, 12 of them are confirmed with eggs. In these 12 nests, at least 5 nests were digged by fisherfolk, and 1 nest was flooded by seawater, the direct loss rate was 50%. In Xisha Archipelago, the main breeding season of green turtle is from June to August, and the egg-laying is commonly occurred from 10 p.m. to 3 a.m. next morning. The green turtle climbs to the sand beach in floodtime, and lays eggs above the high water level. The height above sea level, tide and human disturbance are the main disturb factors to turtle's laying, so the laying area of turtle is the sand beach above 2.5m sealevel and 600-700m far from human community. The main threaten factor to the biodiversity in Xisha Archipelago now is from the destruction of the habitat and the over-exploitation of the resource. All these things are mainly caused by people's killing, destruction and disturbance. The Xisha Archipelago is in the border area of our country, it is important to maintain of the island succession and the defence of national coast by maintaining biodiversity of the island. This research provides a scientific basics for protecting biodiversity and ecological restoration in Xisha Archipelago.