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We measured net photosynthesis rate (Pn), transpiration rate (Tr), and water use efficiency (WUE) of six-year-old Schima superba, Castanopsis hystrix, Michelia macclurel, Castanopsis sfissa, Manglietia glauca and Liquidambar formosana using Li-6400 portable photosynthesis system manufactured by LI-COR company in the upper and middle reaches of Dongjiang watershed. The results showed that all six tree species performed well and maintained higher Pn and Tr under better hydrothermal conditions, when hydrothermal conditions were becoming worse, six tree species were able to adapte by reducing transpiration and increasing water use efficiency. There were large seasonal differences for these parameters, with higher net photosynthesis rate, and transpiration rate higher in August than in October (71.86 % and 129.22 % respectively), while WUE higher in October than in August (25.78 %). According to the value of mean net photosynthetic rates, mean water use efficiency, in both August and October, the order of the six tree species was Schima superba ＞Castanopsis hystrix, Castanopsis fissa, Michelia macclurei ＞Liquidambar formosana and Manglietia glauca. We conclude that Schima superba has higher adaptive capacity to dry environment, followed by Castanopsis hystrix, Michelia macclurei and Castanopsis fissa, and Liquidambar formosana and Manglietia glauc has lowest adaptivity.
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