| Summary: | 碩士 === 國立中興大學 === 森林學系所 === 94 === This study established three 30 m × 100 m sample plots and one hundred twenty 5 × 5 m2 subquadrat in each sample plot for inventorying vegetation and surveying the area of expanded gaps in the costal foreat in Junan, Miaoli. The object of this study was to analysis the effect of the expanded gaps on adding plant diversity . The results inventory of vascular plant found 29 families, 45 genera, 49 species and the family with the largest number of species was Asteraceae, Poaceae and Euphorbiaceae.
There were fourteen gaps in all. Gap areas were from 26.93 m2 to 453.48 m2 and many of them were small than 200 m2. According to the results of Matrix Cluster Analysis (MCA), the types of investigated vegetation in expanded gaps can be classified into as follows: Melia azedarach - Broussonetia papyrifera
- Panicum repens type, Celtis sinensis type and Broussonetia papyrifera type. And the types of investigated vegetation in 5 × 5 m2 subquadrat with different gap area percent is classified by Matrix Cluster Analysis (MCA) into as follows: Celtis sinensis - Panicum respens type, Celtis sinensis type, Melia azedarach - Broussonetia papyrifera type and Broussonetia papyrifera type.
The results proved that the existence of gap encourage understory vegetation to establish in costal forest, for example, Panicum respens often occupied lots of area to be main plant in early gap phase. In early gap phase, only one of wood plant established, which was Celtis sinensis and some of trailing plants which had lived in understory would compete against with each other for habitat in gap. In later gap phase, Bidens pilosa L. var. radiate replaced Panicum respens little by little. Many seeds of shade-intolerant woody species began to germinate and seedling of Broussonetia papyrifera grew more quickly than others due to many sapling of Broussonetia papyrifera in expanded gaps.
The distribution of gaps was one of the factors affects to the establishment of the seeding of Celtis sinensis. Celtis sinensis regenerated well and may become the dominant species in degenerating Casuarina equisetifolia forest in the future. The influence of different gap area percent explain that the number of sapling of Broussonetia papyrifera changed with that and became sapling bank to fill gaps if the gap area percent up than 75 % and habitat is enough.
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