The Ecological Effects Of Fog On Epiphytes In Xishuangbanna Area

Xishuangbanna is located at the northern margin of tropics. Its climate is different from that of typical tropics. The main problems in this area are seasonal drought and low temperature. But the rainforest is not different too much from that of typical tropics in southeast Asia. Fog (including dew) might contribute to the development of rainforest in Xishuangbanna, but related studies are few. Epiphytes are an important special class of plants in the rainforest. They live on stones or stems of other plants and can't uptake water from soil. However, they can survive the six months dry season, and are evergreen all the year round. Fog may play an important role to them. In this study, the following three experiments were conducted in Xishuangbanna to explore how epiphytes adapt to water deficit in the dry season and to analyzed the effects of fog on tropical rainforest.1 Water absorption by leaves in epiphytes and non-epiphytesIn this study, we wanted to know whether (1) leaf could absorb fog water directly and contributed to its water status recovery, and (2) epiphytes were more competent compared to non-epiphytes in leaf water absorption. The study was conducted during dry season in Xishuangbanna, and four species of epiphytes and six species of non-epiphytes were included. The effect of fog was imitated by spraying leaves with distilled water. Leaf water potential (ψ_w), relative water content (RWC) and the amount of water absorbed increased gradually with the time of spraying, indicating that both epiphytes and non-epiphytes could absorb fog water directly through leaf and contributed to water status recovery. But ψ_w increased more quickly in epiphytes than in non-epiphytes. Compared with non-epiphytes the leaves of epiphytes, Bolbitis scandens and Rhaphidophora decursiva, could absorb fog water more quickly and increase RWC more greatly, indicating that they were more competent compared to non-epiphytes in leaves water absorption. Leaf capacity to absorb fog water in epiphytic orchid, Coelogyne occultata and Staurochilus dawsonianus, was lower than in Amischotolype hispida and Mananthus patentiflora, two non-epiphytes, but higher than in other four non-epiphytes measured in this study. ψ_w of epiphytes at early evening when the fog did not...