外來入侵物種問題已日益嚴重,不僅嚴重威脅本土生態系平衡,進而影響當地的經濟發展及造成農產品與生態系的負面影響。目前在台灣南部的恆春半島與澎湖群島是銀合歡主要的擴散地區,故本研究旨在針對島嶼地形的澎湖地區與半島地形的恆春地區,探討銀合歡於這兩地區的空間結構分佈特徵與擴散變遷情形有何異同,從中瞭解這些異同因子,以幫助相關單位更精確地監測與防治銀合歡的擴散。研究方法包括利用文獻回顧法,了解銀合歡的生長物候特性及其入侵擴散的因子,並應用遙測技術使用SPOT衛星影像,經影像分類處理以獲取澎湖地區1993-2005年及恆春半島1994-2006年土地使用圖和銀合歡空間分佈圖,採用檢核區方式評估其分類精確度之後,利用量化的地景指數(Landscape Indices):嵌塊體數(Number of patch)、Shannon多樣性(SHDI)、Shannon均勻度(SHEI)、形狀指數(Shape Indices)等分析兩地區的地景結構及銀合歡的空間分布特性,最後再使用Shannon多樣性指數t檢定法,藉以瞭解澎湖地區與恆春半島地景多樣性和銀合歡擴散是否有顯著性的變遷。 研究結果顯示,銀合歡之分佈主要為距道路兩側0-200m間、低海拔、及人為開發之緩坡地區,分佈趨向為東北-西南方及背風面的西南方處,但無法入侵海拔較高的天然林區。經Shannon多樣性指數t檢定法得知,澎湖地區於1993-2005年與恆春半島於1994-2006年期間的地景具有變遷性,且兩地區的銀合歡對地景的影響也呈現顯著差異。澎湖地區和恆春半島銀合歡的擴散速度與成長量持續擴大中,政府單位應重視入侵物種的嚴重性與危害,及早做好防治措施與經營管理。
Species invasion is an urgent problem in Taiwan currently. It not only threatens native ecological balance, but also affects economical development, agricultural products, and ecosystems. Leucaena leucocephala has been sprawled very seriously in Hengchun and Penghu. The objective of this study aims at the spatial structure analysis of Leucaena leucocephala in the Penghu area and Hengchun Peninsula. The research processes include the collection of literature review to understand the growth characteristics of Leucaena leucocephala and the factors of its invasion and dispersal. SPOT images from 1993-2005 of Penghu area and from 1994-2006 of Hengchun Peninsula are used to generate the land-use map and spatial distribution map of Leucaena leucocephala, and then to assess the accuracy of classification map according to the selected test areas. The quantified landscape indices(e.g., number of patch, Shannon diversity indices, shape indices)are then calculated for analyzing landscape structure, spatial distribution and dispersal change of Leucaena leucocephala. Finally, the Shannon t-test is applied to examine the landscape diversity of study area and see if there is a significant landscape change or not. The results obtained from this study are as follows. The spatial distribution of Leucaena leucocephala mainly locates around the 0-200m from the road and distributes in the gentle slope and low elevation area. The dispersal trend is toward northeast- southwest direction and grows on the lee side of southwest. However, it does not invade the natural forest on high elevation area. The result of Shannon diversity t-test indicates that the landscape and the dispersal of Leucaena leucocephala did show a significant change during 1993-2005 in Penghu and 1994-2006 in Hengchun. Therefore, the result can be a reference for the related forest management units to deal with the issue of Leucaena leucocephala.