It remains difficult to monitor gas exchanges of tall arbor trees using portable equipments, e.g. Li-6400, as it is hard to reach the leaf samples in situ. Due to tree heights, this paper aim to compare the gas exchange between in situ and abscised leaves of Cyclobalanopsis glauca under three habitats with the purpose to identify a possible methodology with which we might take usage of abscised rather than in situ leaves. The result showed that after the samples were abscised, the leaf stomatal conductance (gs ) immediately increased before dropped gradually in later. The extent of this change was found to be temperature-dependent. The linear relationships either between gs and transpiration (E), or between gs and photosynthesis (Pn) were significant but the former had a higher correlation, indicating the opening of stomata influenced more intensively on E than on Pn. Temperature is a key factor influencing the variation of gas exchanges of the abscised leaves, with higher temperature in karst area resulted in a rapid E loss and leading to water stress occur earlier to the partly stomatal close, which in turn decreased the Pn. The reliable duration for measuring the gas exchanges from the abscised leaves is determined by leaf temperature. In karst area where the leaf temperature was frequently over 32℃ in summer, the reliable duration lasted only 3-6 min after abscission, while in Guilin Botanical Garden (non-karst) with leaf temperature was about 32℃, the reliable duration lasted a 10 min, whereas in the green house at temperature around 20℃, the reliable duration possibly will go for 20 min.