由於琉球嶼過去的調查都是以定性植物名錄記錄為主,缺乏以定量的研究方式來對植物社會作描述。因此,本研究的目的是希望能藉由定量的方式分析琉球嶼群落組成變化,以及討論影響植物或樣區於空間分布上的環境變數。樣區調查方式採用Braun-Blanquent的單一樣區法,依植群發育、配置與型態的不同,乃設計不同的取樣面積大小,於次生林設置10 m × 10 m樣區,灌木叢與草原則設計為4 m × 4 m 樣區,沿岸植群則為2 m × 2 m的樣區。植群取樣結果共調查了60個樣區並記錄9項環境變數,調查結果為原生維管束植物共計有67科194屬279種,物種數量最多的前3科為禾本科45種、大戟科26種、豆科20種;而歸化植物約佔全島植物14.2%,分屬24科54屬62種。使用雙向指標種分析與忠誠度分析配合Fisher’s 顯著性測試(p < 0.001)進行植群區分,結果將琉球嶼的植群區分為7個植群型:(一)煉莢豆-岐穗臭根子草型;(二)海雀稗-草海桐型;(三)馬鞍藤型;(四)野牽牛-構樹型;(五)山柚-構樹型;(六)竹葉草-姑婆芋型;(七)長葉腎蕨-雀榕型;分布序列則以典型對應分析和Monte Carlo排列顯著性測試主要的環境梯度,且利用前進選擇法挑選具有顯著性的環境變數,結果顯示與第1、2梯度軸具顯著性,而銀合歡覆蓋豐富度、地表裸露、坡度、土壤含石率與土壤質地為影響植物組成和社會的重要環境變數。
In the past the Liuchiu Island was with mainly plant qualitative information, but no quantitative method to describe plant community was available. Therefore, the aims of this research were used quantitiative analysis on community composition variation, and discussed species or plot correlation with environmental gradients. Using Braun-Blanquent single-plot sampling, according to vegetation development, deployment and the different types to design vary plot: secondary forest of 10 m × 10 m plot, brush and grass of 4 m × 4 m plot and littoral vegetation of 2 m × 2 m. Sixty plots were taken and recorded nine environmental parameters for each plot. The results showed that the floristic data consists of 279 native species including 194 genera and 67 families, of which 62 species were naturalized. The important families were Gramineae (44 species), Euphorbiaceae (26 species), Leguminosae (19 species). Two-way indicator species analysis (TWINSPAN) and species fidelity with Fisher’s exact test (p < 0.001) were used to identify plant communities. The communities were classified into seven vegetation type: Alysicarpus vaginalis-Bothriochloa glabra type, Paspalum vaginatum-Scaevola sericea type, Ipomoea pes-caprae subsp. Brasiliensis type, Ipomoea obscura- Broussonetia papyrifera type, Champereia manillana- Broussonetia papyrifera type, Oplismenus compositus)-Alocasia odora type, Nephrolepis biserrata-Ficus superba var. japonica type.Canonical correspondence analysis (CCA) and Monte Carlo permutation test were applied to determine the main environmental gradients. Foreward selection was used to pick out the significant environmental variables. The first and second axle of ordination were significant, and Leucaena leucocephala cover-abundacne, percentage of bare ground, slope, stoniness of soil and soil texture were important variables to illustrate the floristic variation and community types.