Abstract: Based on the analyses of daytime thermal effect s of different thermal active surfaces in canopy gaps in t ropical seasonal rain forest in the cool2fog and hot-wet season in Xishuangbanna , the thermal characteristics of different thermal active surfaces in canopy gaps are described. The finding showed that : The thermal effect of vertical thermal active surfaces is not negligent , not only in the cool-fog season , but also in the hot-wet season. Moreover , influenced by the height of t rees that form the edge of the gap , the height of maximum area of thermal effect of vertical thermal active surfaces at the east and north edge of gaps in tropical seasonal rain forest was higher than that in secondary forest ,but the intensity of thermal effects was weaker , compared to secondary forest . This indicates that , besides solar angle , time and intensity of radiation , the height of t rees is also an important factor that influences thermal effect s of vertical thermal active surface of edges. The results supply a research basis for understanding microclimatic formation of canopy gaps , for studying forest succession and effects of forest biodiversity.

Key words: diversity, vesicular arbuscular mycorrh iza, colonization