On the subzone demarcation in Hainan Island

Obvious differences exist between southern and northern natural conditions of Hainan Island which lies in the tropical area and can be divided into two parts: the southern tropics and the northern tropics. Some scientists also attempted to draw subzone demarcation. Dipterocarpaceae forest, as a sign of tropical forest in Asia, is distributed mainly in southeast of Hainan Island. In addition, plants of Dipterocarpaceae are dominant in tropic evergreen monsoon forest and belong to a zonal vegetation type of Hainan. The authors evaluated the demarcation line on the basis of the distribution of typical forests, Dipterocarpaceae forests, and draw a new line that across from Changjiang through Baisha and Qiongzhong to Wanling. The ecology and geographical distribution of Dipterocarpaceae forests are described.