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Ecology and Conservation

Research Report

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Key word: Flora, vegetation classification, succession seres, restoration plan

The Penghu Southern Four Islands National Park is located at the southern area of Penghu county, while the boundary is among 119º30’E–119º41E and 23º14’N–23º16’. It includes four major islands Dong-Ji island, Si-Ji island, Dong-Yuping island and Si-Yuping island, and subsidiary islets. The main vegetation type of these islands are grasses and forbs, and the species are composed of Poaceae, Fabaceae, Malvaceae and Cyperaceae. The number of exotic species on these islands are one-third of all the vascular plants. These exotic plants are including dominated Leucaena leucocephala (Fabaceae) and Euphorbia tirucalli (Euphorbiaceae), which were used for charcoal-making and coastal defense during the Japanese colonized period. The main purpose of this study is trying (1) to investigate the flora of the Penghu southern islands; (2) to analyze the relationships between environmental factors and the vegetation; (3) to estimate the potential succession series and (4) to propose the restoration strategy and plan for the references and policy-making of Marine National Park.

We used transection method to investigate the vascular plants including the major four islands and a subsidiary islet (Chu-Tou island) from the late April to early September. We also established 81 vegetation survey plots of standard size with 25 m2 for vegetation classification and collected the soil to analyze the properties, measured the wind speed, wind directions. Ordination analysis were applied to find out the relationships between vegetation types and environmental factors. Then calculating the succession index of each vegetation type to estimate the succession seres and propose restoration plans.

During the investigation period, we identified 221 species of 57 families, including 119 native species in the southern islands, seven endemic species/subordinate species. There are 87 exotic species, including 19 cultivated species and 68 naturalized species. However, there are eight native species of Flora of Taiwan, but they were cultivated in the Penghu southern islands. We classified the vegetation into seven types: I. Tetragonia tetragonoides-Leucaena leucocephala type, II. Epaltes australis-Fimbristylis cymosa type, III. Portulaca pilosa-Evolvulus alsinoides type, IV. Imperata cylindrica var. major-Vitex rotundifolia type, V. Wedelia prostrata-Cassia sophora var. penghuana type, VI. Bothriochloa glabra-Sorghum nitidum fo. aristatum type, VII. Sporobolus virginicus-Peucedanum japonicum type. The succession degree suggests that the vegetation type III in plateau would be the early stage of succession seres, and it would become vegetation types IV, V and VI. The succession seres of coastal region are early seral stages (types II and VII). If the continuous expansion of Leucaena lecocephala proceeds, these two types would become type I. For the broad view of the Penghu islands, major vegetation of the southern Penghu four islands belongs to the early seral stage and disturbed by wild goats continuously. We also found that the species diversity would be affected by the wild goats in the Penghu southern four islands, but it needs to be confirmed by further experiment.

According to the results of this study, we suggest:

1.For immediate strategy:
Since the dominated species of Penghu southern islands are herb species, the feasibility of restoration such herb species is low. Therefore we suggest that the economic plants and endemic plants can be used for priority restoration plan, such as Glossocardia bidens and Cassia sophora var. penghuana
2.For long-term strategy:
We suggest that the influence of wild goats on local flora and vegetation should be examined through field experiment in the future.
We suggest to monitor the change of plants and vegetation in vulnerable area of the Penghu southern islands, such as coastal regions, etc

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