Tropical Geographical Elements of Woody Seed Flora in Shaanxi, China

The tropical geographical elements of woody seed plant in Shaanxi province were investigated and were found to belong to six categories,which included Pantropic,tropical America and Tropical Asia disjuncted,Old World tropics,Tropical Asia to Tropical Australasia,Tropical Asia to Tropical Africa,and Tropical Asia (Indo-Malesia).The dominant element of the tropical geographical composition was the Pantropic and there are 37 genera and 197 species in Shaanxi province.The distributions of the elements were mainly in the southem region of the Qinling Mountains. The nature of Shaanxi woody flora was determined to be temperate based on arealtype of family，genus and species and the phytocoenology function of the woody tropical geographical elements.The Floristic transition from tropical to temperate in Shaanxi was very obvious.