台灣中部馬海濮富士山櫟林帶之植群分析

Abstract

馬海濮富士山位於台灣中部，中央山脈西側，該區除西南角有造林外，林相完整。本研究針對馬海濮富士山區，海拔1800-2600 m的區域，設立48個20 m × 20 m的樣區，進行植群分析。 樣區中胸高直徑大於1cm之木本植物均加以調查，共發現124種木本植物，分屬38科71屬。以科之物種數而言，殼斗科最具優勢，松科次之；最優勢的物種為赤柯，其次分別為台灣鐵杉、紅檜、台灣雲杉及長尾尖葉櫧等。 植群分類第一階段以TWINSPAN進行分析，可分出8個植群型，將其中兩個屬於演替早期的林型分離，再以所剩40個樣區以群團分析進行分析，可得到9個林型；綜合上述分析結果，將馬海濮富士山區櫟林帶分成11個植群型。以最優勢種命名分別為：台灣赤楊林型、台灣二葉松林型、紫珠葉泡花林型、長尾尖葉櫧林型、台灣杜鵑林型、台灣扁柏林型、假長葉楠林型、紅檜林型、赤柯林型、台灣雲杉林型及台灣鐵杉林型。配合DCA分析結果顯示，海拔高度及地形是影響植群型的主要環境因子。各植群型呈現不同的結構、物種組成及歧異度。 選擇株數達20株以上或最優勢之樹種，將各樹種依林型作徑級結構圖。就各林型冠層優勢樹種與林型內其他物種更新情況而言，紫珠葉泡花林型、長尾尖葉櫧林型、台灣扁柏林型、假長葉楠林型與赤柯林型，因優勢種與林型內多數物種均呈反J型，若其環境因子無重大變化，物種組成不會有大更動。台灣鐵杉林型、台灣二葉松林型與台灣杜鵑林型，冠層優勢物種呈鐘型偏左，推測在一段時間後，該林型內物種組成將有明顯變化。而台灣赤楊林型、紅檜林型與台灣雲杉林型，冠層優勢樹種呈鐘型偏右，這些物種被認為是不耐蔭的物種，必需靠大型擾動才能更新。

Mt. Ma-Hai-Pu-Fu-Shih is located on the western side of the Central Mountain Range in central Taiwan. With the exception of an area of reforestation in the south-western region, all the other areas are made up of natural primary forests. This study of vegetation analysis focuses on the Quercus Forest of Mt. Ma-Hai-Pu-Fu-Shih. I set up 48 20m x 20m plots located at an elevation of 1800-2600 m above sea level. Within each plot, all free-standing woody plants with dbh≧1cm were identified and measured. In total of 124 species, 38 families and 71 genera are represented in the plots. Of these, the most speciose family was Fagaceae followed by Pinaceae. In terms of Important Value, the most dominant species were Cyclobalanopsis morii, followed by Tsuga chinensis var. formosana, Chamaecyparis formosensis, Picea morrisonicola and Castanopsis carlesii. Using the TWANSPAN for the initial stage of vegetation classification, a total of 8 vegetation types were defined. Among them two are considered to be the successional forest types. Leaving out the plots of successional forest type, the remaining 40 plots were divided into 9 different forest types using Cluster Analysis. Consequently, 11 vegetation types were derived with the combination of the above two methods, and are designated as follow: Alnus formosana forest type, Pinus taiwanensis forest type, Meliosma callicarpaefolia forest type, Castanopsis carlesii forest type, Rhododendron formosanum forest type, Chamaecyparis obtusa var. formosana forest type, Machilus japonica forest type, Chamaecyparis formosensis forest type, Cyclobalanopsis morii forest type, Picea morrisonicola forest type and Tsuga chinensis var. formosana forest type. DCA results revealed that elevation and topography were the major environmental factors affecting forest types. Each vegetation type exhibited different structure, species composition and species diversity. To understand the regeneration of each vegetation type, size-class distribution analyses were constructed and only species with more than 20 stems and the dominant species were included. Size-class distribution showed a clear inverse J-shape pattern for most species in the forest types ( including Meliosma callicarpaefolia forest type, Castanopsis carlesii forest type, Chamaecyparis obtusa var. formosana forest type, Machilus japonica forest type and Cyclobalanopsis morii forest type ) suggesting a good regeneration potential. However, dominant species of the Pinus taiwanensis, Rhododendron formosanum and Tsuga chinensis var. formosana forest types displayed a unimodal size-class distribution with highest stem densities in the 5-10 cm size class and with low level of recruitment. Dominant species in the Alnus formosana, Chamaecyparis formosensis and Picea morrisonicola forest types exhibit a negatively skewed unimodal distribution. These species are thought to be shade-intolerant, requiring large-scale disturbance in order to regenerate.