科研之友
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摘要
Recent studies on bryophyte and macrolichen diversity in lowland forests of northern South America have shown the existence of a novel forest type, the %26quot;tropical lowland cloud forest%26quot; (LCF). LCF is very rich in epiphytes and occurs in lowland river valleys where radiation fog in the morning provides an additional input of liquid water. Because of their dependence on frequent precipitation and low evaporation, Hymenophyllaceae (filmy ferns) are a suitable group for studying moisture availability. We sampled epiphytic Hymenophyllaceae on 32 trees in French Guiana, 16 in LCF and 16 in adjacent rain forest (LRF). Abundance of Hymenophyllaceae was significantly higher in LCF than in LRF. Only 10% of trees in LRF were inhabited by filmy ferns, in contrast to 70% in LCF. Moreover, the number of species recorded in LCF (9) was more than twice as high than in LRF (4), and the mean number per tree 8 times higher. Species restricted to the understory of LRF occurred in the canopy of LCF. We attribute the detected differences in diversity and vertical distribution of Hymenophyllaceae in the two forest types to the occurrence of fog in LCF, enhancing the availability of liquid water and thus Facilitating the establishment and growth of the filmy ferns. Also, radiation protection against evaporative loss seems to play a crucial role in the vertical distribution of filmy fern diversity. The observed differences in filmy fern diversity and distribution in LCF and LRF represent novel traits separating the two forest types, and indicate that Hymenophyllaceae species are sensitive indicators of lowland cloud forest.
- 出版日期2012
