西藏壳斗科的地理分布

在野外考察、分类清理和修订的基础上讨论了西藏壳斗科的地理分布。自然分布的西藏壳斗科植物，共３属３３种，集中分布于藏东南的河谷地带和喜马拉雅山脉的聂拉木县，印度栲、刺栲、喜马拉雅石栎和西藏石栎是这些地区海拔２００米以下群落建群种；通麦栎、俅江栎和薄片青冈是西藏海拔１８００－２５００米地段森林植物被的建群种；硬叶高山栎类则是海拔２５００米以上硬叶常绿阔叶林及高山灌丛植被的建群种。种的区系成分分析表明：

DISTRIBUTION OF FAGACEAE IN TIBET

Distribution of Fagaceae from Tibet has been discussed based on field expedition in Tibet and taxonomical research at present paper.There are 3 genera including 33 species of Fagaceae in Tibet,Castanopsis with 7,Lithocarpus 11,Quercus 15(subg.Cyclobalanopsis8).Most of them are concentrated in river gorge area of southeast Tibet particularly, Medog and Nyalam of Himalayas.Castanopsis indica,C. hystrix,C.tribuloides,Lithocarpes collettii and L xizangensis are dominant elements in vegetation of river gorge area altitude below 2000 meter of southeast Tibet and Q.lanata,Q. kiukiangensis and Q. Iamellosa are dominant in the area of southeast Tibet,altitude range from 1800 to 2500 mcters.Above 2500 meters in this area Q.aquifolioides is dominant.Floristic elements analysis are also made at present paper.Beech plants in Tibet are divided into 7 kinds of floristic elements.They are tropical India,Himalaya to Indo-China distribution pattern,Indo-China to west Himalayan distribution pattern,Himalayan to Japan distribution pattern, Sino-Himalayan distribution pattern,endemic to east Himalaya,endemic to Tibet and endemic to China distribution. Among of them,tropical India,Himalaya-Indochina, Sino-Himalayan and endemic to east Himalayan are the most ahundant.Based on floristic elements analysis it can be concluded that the beech plants which distribute below 2000 meters come from tropical Asia and those distribute above 2000 meters come from tropical Asia and those distribution above 2000 meters come mainly from east Asia paticularly Hengduan Mountains.Geological background of Tibet are also discussed.