| Xishuangbanna, located in southwest China, is at a biogeography transition zone between tropical Asia and temperate East Asia, and is one of the most biodiversity richness regions in China. However, under the driving forces of increasing population and economic benefits, virgin forests were seriously destroyed in recent years. Even the dipterocarp forest, which is dominated by the species Parashorea chinensis, a first grade protected species at national level has been dramatically changed in its distributional area. By the case study, we will discuss the changes of land-use/land-cover and species diversity of the tropical region.Based on the Landsat TM/ETM images from 1988 and 2003, and the field investigation data of 2006, and by using remote sensing and geography information systems, the land-use/land-cover change in the distributional area of Paroshorea forest in Xishuangbanna in the past 20 years was discussed, and also its driving forces were analyzed. On the other hand, based on a comparison of the plots of Parashorea forest in 1988 and 2006, the changes of the structure, species composition, life form, plant abundance and species diversity of Parashorea forest in the past 20 years were analyzed. The following results are given:1 Remarkable land-use/land-cover changes had happened in the study area between 1988 and 2006. Because of the increasing demand for natural rubber, the expansion of rubber plantations resulted in the dramatic decrease of natural forests, especially the tropical seasonal rain forest at lower elevation. The study area is about 125km~2, and rubber plantations increased at a rate of 120.56hm~2/a, while the tropical seasonal rain forest had a decrease at a rate of 111.35hm~2/a. In recent years, rubber plantations expanded to higher elevation, which directly led the decrease of tropical mountain evergreen broad-leaf forest. Arable lands increased during 1988 and 2003 but decreased rapidly from 2003 to 2006. Water area increased from 2003 to 2006, and so did the construction area.2 Combined the social economical data of the research area, we found that markets, policies, increasing population, and the pursuing for economical profits were the main driving forces, which led to a series of domino effects on natural resources and environment. We suggest the local government take strong actions to control the further expansion of rubber plantation, and to realize the sustainable and harmonious development of economy, society and natural resources in the biodiversity richness regions.3 By analyzing the changes of species diversity of the Parashorea forest in the past 20 years on plot data, we found that the species Parashorea chinensis still had the greatest dominance and the forest was still a single species dominant community that dominated by Parashorea chinensis. The change of tree species dominance was obvious, some species declined, and some became more dominant. In the two plots of 1988, 52ï¼…and 42ï¼…of the tree species were absent and replaced by other new migrants respectively. In addition, the classes and numbers of saplings, shrubs and lianas increased, but the number of herbs and epiphytes decreased.4 The increase of saplings, shrubs, lianas and the decrease of herbs and epiphytes explain that besides the impacts of the succession itself, the community was also disturbed by outside environment. The habitat of the community could become drier than before, which resulted in the decrease of chamaephytes and epiphytes and the increase of lianas and microphaenerophytes. In addition, the obvious replacement of tree species was not at the natural regenaration rate of the community, the increasing disturbance of the outside environment undoubtedly accelerated this replacement.
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