臺灣北部直潭山植群之分析

Abstract

本研究主要目的為調查直潭山的植群，並加以分析，除了期望能將植群分群、了解其特性外，也欲篩選出與植物社會有最密切交互作用之環境因子，以提供生態保育及經營上之參考。直潭山因保有一定面積之次生林相，故為提供低海拔山區植群研究的一個優良地區。本研究除了進行植群分析外，也採用不同之取樣方法，與前人研究結果進行比較，並對區域內珍貴稀有植物進行調查，以供相關研究及保育之參考。 本研究設置了56個樣區，分布於直潭山的各稜線及不同面向之山坡，並調查了5種環境因子。調查區域中，所記錄到的維管束植物包括蕨類植物26科102種、裸子植物2科2種、雙子葉植物73科220種、單子葉植物13科48種，共計114科372種植物。本區植物社會的Shannon歧異度指數為3.753，各單位的均勻度指數多高於0.7，顯示區內植物多樣性高。 經過雙向指標種分析、降趨對應分析以及矩陣群團分析後，大致可將研究區域內的森林分為2個型及5個亞型，分別為： A、 豬母乳－長梗紫麻型（Ficus fistulosa－Oreocnide pedunculata type） A1、豬母乳－楓香亞型（Ficus fistulosa－Liquidambar formosana subtype） A2、大葉楠亞型（Machilus japonica var. kusanoi subtype） B、 豬腳楠－山紅柿型（Machilus thunbergii－Diospyros morrisiana type） B1、豬腳楠－墨點櫻桃亞型（Machilus thunbergii－Prunus phaeosticta subtype） B2、豬腳楠－奧氏虎皮楠亞型（Machilus thunbergii－Daphniphyllum glancescens subsp. oldhamii var. oldhamii subtype） B3、大明橘－小葉赤楠亞型（Myrsine seguinii－Syzygium buxifolium subtype） 此分群結果與其他鄰近地區之研究結果相比較，大致符合。 結果另顯示，少數大面積樣區的取樣方式與多數小面積樣區的取樣方式，所獲得的結果大致雷同，而本研究所採56個廣散之小樣區的取樣方式部分效果較佳，可供往後研究試驗設計及規劃之參考，以擇定最有利的取樣方式。本區植物分布主要受地形、海拔高度影響，其他因子如坡度及岩石覆蓋度亦參與交互作用，並於統計上達到顯著的水準。根據重要樹種生長曲線，可推測研究區域之森林可能因干擾的存在而未達極盛相，若未來能排除這些干擾，本區域植群應能漸趨極盛。

The aim of this study is to investigate and analyze the vegetations of Mt. Chi-tang, besides the intention of understand the classification of the vegetation and its properties, we also hope to sieve out those environment factors which have the most interactions with the vegetation, in order to provide advices for ecological conservation and management. Mt. Chi-tang provides low altitude mountain vegetation research a good region because it retains a proper area of secondary forest stand. In addition to analysis the vegetation, we adopted a different sampling method to compare with the result of formal study, and we investigated the rare and endangered plants as well in order to provide some references for related research and conservation. A total of 56 plots were set up in the study area, including all ridges and different aspects of hillsides, and all plots were provided with measurements of 5 environmental factors. A total of 372 vascular plant species which is composed of 102 pteridophyte belonging to 26 families, 2 gymnosperm belonging to 2 families, 220 dicotyledon belonging to 73 families, and 48 monocotyledon belonging to 13 families were recorded in the research area. The Shannon diversity index of the whole area is 3.753 and the evenness indices of most individual units are beyond 0.7, showing a high diversity of plant species in the study area. According to the results of the two-way indicator species analysis（TWINSPAN）, detrended correspondence analysis（DCA）, and matrix cluster ananlysis（MCA）, the following 2 main vegetation types and 5 subtypes are recognized： A、 Ficus fistulosa － Oreocnide pedunculata type A1、Ficus fistulosa － Liquidambar formosana subtype A2、Machilus japonica var. kusanoi subtype B、 Machilus thunbergii － Diospyros morrisiana type B1、Machilus thunbergii － Prunus phaeosticta subtype B2、Machilus thunbergii － Daphniphyllum glaucescens var. oldhamii subtype B3、Myrsine seguinii － Syzygium buxifolium subtype This classification result is approximately correspondent with those gained nearby. The result also shows that the outcome of the sampling method which have less bigger plots and the sampling method which have more smaller plots are approximately the same, however, the method of using 56 widespread small plots brings some better resutls, this can provide some reference for experimental designing and planning of future researches, in the attempt to select the most favorable sampling method. The distribution of plant species in the study area is mainly determined by topography and altitude, but other factors including slope and coverage of rock are also partially related, achieving a statistically significant level. According to the growth curves of the important tree species, we presume that the researched forest have not reach the climax status due to the existence of disturbance, but if these disturbance can be removed in the future, the vegetation in this area could gradually reach climax.