| Summary: | 碩士 === 國立臺灣師範大學 === 生命科學研究所 === 99 === Species interaction is a widely studied ecological issue. In addition to the most frequently studied negative interaction—competition, there is also positive interaction. However, positive interaction is much less explored compared with competition. Recent studies indicate that positive interaction helps to maintain biodiversity. Global change is expected to increase stress to organisms and studies suggest that positive interaction is more common in stressed environments. Although some studies have examined positive interaction between epiphytes and their host trees, barely any studies examined interaction between epiphytes. Asplenium antiquum and Haplopteris zosterifolia often co-occur at Fushan Experimental Forest. I conducted field survey and removal experiments to examine if there is positive interaction between the two epiphytic ferns and if so what are the causes? My field survey indicates that most H. zosterifolia (56%) co-occurred with A. antiquum whereas the latter showed no preference for the co-occurrence with the former. The size of H. zosterifolia plants that co-occurred with A. antiquum was larger than those that did not whereas the size of A. antiquum did not differ between those that co-occurred with H. zosterifolia and those that did not. The result suggests that H. zosterifolia probably has a neutral effect on the growth of A. antiquum whereas the latter has a facilitative effect on the growth of the former. Removing H. zosterifolia had no effect on the number and length of fronds of A. antiquum which supports its neutral effect on A. antiquum. Removing both the substrate and fronds of A. antiquum led to shorter fronds of H. zosterifolia and such effect was not detected when only the fronds of A. antiquum were removed. Chemical analysis of fronds indicates that the content of N, Ca, and Mg of A. antiquum did not differ between control and H. Zosterifolia removal treatment but the control group had higher C and lower P. I did not have explanation for such differences but the difference in P was not observed in the fronds of H. Zosterifolia among the three treatments (control, A. antiquum frond removal and A. antiquum frond and substrate removal). Overall the result shows only very weak evidence of the co-occurrence of the two epiphytic ferns on their nutrient content. Changes in solar radiation was not the major effect of A. antiquum on H. Zosterifolia because when only the fronds were removed although the light environment changed there was no significant effect on the growth of H. Zosterifolia. The removal of A. antiquum did not have significant effect nutrient content of the fronds of H. Zosterifolia so the facilitative effect should not come from nutrient enrichment. Because epiphytes have no direct asses to soil water and the substrate of A. antiquum has very high water holding capacity, I suspect that the facilitative effect comes from the alleviation of drought stress from the water in the substrate. However, more studies are needed to validate my inference.
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