Master thesis at the School of Forestry and Resource Conservation, National Taiwan University (July 2022)

https://doi.org/10.6342/NTU202202203

Author: Teng Hsin-Yen (鄧信彥)

Advisor: David Zelený, co-advisor: Kuo-Fang Chung

Phytosociology is a branch of vegetation ecology, which not only studies the relationship between different plant communities, but also the interaction between species and the environment within the communities. Phytosociology is also used for plot-based vegetation classification based on their complete floristic composition, an approach introduced by Josias Braun-Blanquet. The aim of vegetation classification is to summarize the spatial and temporal variation of vegetation using a limited number of abstract entities.

Owing to geographical location and large variation of elevation, Taiwan has high diversity of forest types. Montane cloud forest is one of the most endangered ecosystems in the world and can be also found in montane regions of Taiwan at altitudes between 1500 and 2500 m a.s.l., and characterized by frequent ground fog occurrence. Cloud forest in Taiwan is dominated by either a mix of deciduous broad-leaved, coniferous, and evergreen broad-leaved species or purely evergreen broad-leaved species. There are many researches focus on tropical montane cloud forest, while the studies related to sub-tropical montane cloud forest, which distributes wider range than tropical ones in Taiwan, are much less than the former one.

Lalashan and Tamanshan is located in the northern part of Syuehshan Range, and the region around these two peaks is part of the range of the sub-tropical montane cloud forest in Taiwan. In this study I set the lower boundary of the studied region at 1700 m a.s.l. The aim of this study was to classify the old-growth natural forest into a set of vegetation types, describe compositional and environmental difference between these types, and related them to vegetation types published in the literature.

Datasets used in this study include 15 plots sampled between 2003 and 2007 as a part of a National Vegetation Diversity Inventory and Mapping Project, six plots within the project Changes in species- and community-level properties of forest vegetation along cloud and chronic-wind gradients in Taiwan, and 20 plots surveyed by me. The results of vegetation classification based on Cocktail Determination Key (Li et al., 2015) contain nine vegetation types: Yushanio–Fagetum hayatae, Tsugo formosanae–Chamaecyparidetum formosanae, Vaccinio lasiostemonis–Tsugetum formosanae, Elastostemato trilobulati–Tsugetum formosanae, Rhododendro formosani–Chamaecyparidetum formosanae, Adinandro lasiostylae–Chamaecyparidetum formosensis, Arachniodo rhomboideae–Chamaecyparidetum formosensis, Quercus morii–Plagiogyria glauca, and Hydrangea angustipetala–Quercus sessilifolia. Elevation, wind speed, and fog frequency are important environmental factors for describing differences among these vegetation types. There is some difference between vegetation types occurring in study region and the description in published literatures. The reason might be the scales from the present study and published literatures are different: local scale v.s. regional scale. Another reason may be historical or illegal log events which affect the forest stratified structure.

The result of the difference from wind speed and aspect suggests that the vegetation types in Lalashan and Tamanshan are not influenced by northeast monsoon. Besides, all the vegetation occurring in study region may be strongly related to fog frequency gradient. It suggests that fog plays important role in these vegetation types. Therefore, for phytosociological study in this area, the future research should focus on fog or humidity and how to quantify the width of ridges, and survey more sites to obtain more complete species composition and environmental data.

Keywords: montane cloud forest; environmental factors; fog frequency; vegetation classification; vegetation type

植物社會學是生態學的分支，除了探討不同植物社會彼此間的關係，以及其中物種與環境間的交互作用，植物社會學也可以用具有完整植物物種組成資料的樣區為基礎進行植群的分類，而這也是由瑞典植物學家Josias Braun-Blanquet 開始推行的研究方法，而植群分類的目的則是使用簡要且實質的因子描述植物社會的時空變化。

由於地理位置與海拔高度落差，造就了臺灣森林的多樣性，其中也包含在全球面臨生存壓力的山地雲霧林。即使有許多山地雲霧林的學術研究，但大多數集中於熱帶地區，亞熱帶山地雲霧林鮮少被作為研究對象。臺灣的雲霧林通常是由落葉闊葉樹、針葉樹與常綠闊葉樹形成的混合林，或是由常綠闊葉樹形成的單純林相，而海拔1500至2500公尺為臺灣亞熱帶山地雲霧林的分布範圍。

拉拉山與塔曼山坐落於雪山山脈北緣，且位於臺灣亞熱帶山地雲霧林的範圍，並涵蓋於為保護臺灣水青岡、紅檜與臺灣扁柏而設立的插天山自然保留區內。然而，在兩座山周圍區域的植物物種組成並非完全相同，且自1998年以後，已經沒有針對鄰近區域整體植群的相關研究，而前人研究也未依照Braun-Blanquet所推行的方法進行植群調查與分類。本研究將海拔高度1700公尺以上設為研究範圍，以探討存在於兩山區域內成熟天然林之植群型，除了將其分類及描述不同植群型間物種組成與環境條件的差異，也會與已發表的植群型連結並比較。

植群資料包含15個於2003至2007年間由《國家植群多樣性調查與製圖計畫》所調查的樣區，6個由《臺灣森林中物種以及群聚層級之特質沿著雲霧和強風梯度的變化》計畫中所調查的樣區，以及20個由筆者所調查，共計41個樣區，以李等人於2015年發表的雞尾酒鑑定檢索表（Cocktail Determination Key）為基礎分成九種植群類型：玉山箭竹–臺灣水青岡型、臺灣鐵杉–臺灣扁柏型、毛蕊花–臺灣鐵杉型、裂葉樓梯草–臺灣鐵杉型、臺灣杜鵑–臺灣扁柏型、毛柱楊桐–紅檜型、斜方複葉耳蕨–紅檜型、森氏櫟–臺灣瘤足蕨型與狹瓣八仙花–毽子櫟型。海拔高度、風速及雲霧頻度在九種植群型中是重要的環境因子，且在不同植群型間有所差異。而前七種植群型為依照前人文獻所以描述的植群類型，但在研究範圍內情況卻與文獻中有些許不同，可能是因為本研究限縮在局部尺度，而其他的文獻考慮的資料範圍延伸到區域尺度，或是與以前的伐木事件造成森林結構上的差異。

從風速與坡向的到的結果顯示，東北季風在拉拉山與塔曼山的可能不會對本地的植群造成顯著的影響，而在研究中描述所有植群類型的出現，可能都與雲霧梯度有強烈的關聯性。因此，雲霧或濕度、如何量化稜線的寬度以及調查更多樣區讓物種組成和環境資料更加完整，都是未來進行植群研究時可以考慮著重的方向。

關鍵字：山地雲霧林 ； 環境因子 ； 雲霧頻度 ； 植群分類 ； 植群型