北臺灣地區歸化豆科植物對於植物群落衝擊之研究

The Impacts of Naturalized Legumes on Plant Communities in north Taiwan

蔡正國(Jenn-Kuo Tsai)

指導教授 ： 林登秋 ； 吳姍樺

國立臺灣師範大學/理學院/生命科學研究所/碩士(2009年)

摘要

第一章、北臺灣地區植物入侵之概況

對於未來進一步的研究而言，包含有分類組成、相對覆蓋度、相對頻度、生活型、原產地及原產地之氣候類型等詳盡的歸化植物基本資料是不可缺少的。為深入探討歸化植物的特性，我們建立了下列兩個假說並驗證之：(1) 由於北臺灣擁有多樣的氣候及地形條件，包括熱帶及亞熱帶氣候的低海拔平原及溫帶氣候的高海拔山地，容易受到來自世界各地的外來植物所入侵；(2)在北臺灣地區成功建立族群的大多數歸化植物，其原產地的氣候條件與北臺灣相符合。
野外調查部份在北臺灣各縣市進行，利用1-km2之網格系統隨機選取100個網格做為實驗樣區，在每個樣區中的各種棲地類型隨機選取五至十個不等之1-m2樣點，記錄日期、GPS、海拔高度、原生及歸化之植物種類及植物覆蓋度；另外，計算每一種歸化植物的重要值指數(IVI)做為優勢度之指標。調查總共在2242個樣點記錄了12種棲地類型及629種植物，其隸屬於130個科及409個屬。依據各歸化類群所擁有的物種總數來排序，菊科、禾本科及豆科為最優勢的三個科，旋花屬則為最優勢的屬；此外，依據重要值指數排序，大花鬼針草為最優勢的歸化物種。就原產地而言，在北臺灣的大部份歸化植物來自熱帶美洲。

第二章、北臺灣地區歸化豆科植物對於植物群之衝擊

過去研究顯示，入侵植物常對於當地的生物多樣性造成衝擊，包括競爭排除、竭盡水源或改變微棲地物化性質等。其中，改變微棲地物化性質往往造成深遠且不可逆的影響；然而，此環節卻鮮少被討論。在眾多改變微棲地物化性質的機制中，固氮作用是最常見且能改變土壤物化性質的重要機制之一。一般而言，豆科(Fabaceae)植物能藉由固氮作用適應當地環境並增加該地區土壤的生物承載量，進而改變該地區植物之生物量及多樣性。
本研究設立下列四個假說以探討歸化之豆科植物在北臺灣植物群落之生物量及多樣性所造成之衝擊性：(1) 歸化豆科植物的存在與相對較高的植物生物量及多樣性有關；(2) 歸化豆科植物提昇了土壤含氮量；(3) 歸化豆科植物同時增加原生及外來植物之生物量及多樣性；(4) 歸化豆科植物在不同棲地類型之植物群落造成之衝擊性會有所不同。
實驗以北臺灣為樣區，利用每平方公里之網格系統，隨機選取100個1km2樣區，利用正射化影像(Othophoto)判定棲地類型，並各自選取五到十個不等的1m2小樣方，記錄GPS、海拔高度、棲地類型、植物種類以及覆蓋度等，並轉換成多樣性指數包括Shannon(H’)、Simpson(λ)、Pielou均勻度指數(J)、Berger-Parker優勢度指數(BP)、物種數(S)及總覆蓋度(C)等六項指數；另外，收集土壤樣本以評估歸化豆科植物之存在與否造成含氮量之差異性。
結果顯示，在100 km2中2242m2的小樣方共記錄了16種歸化豆科植物，其中以大葛藤 (Pueraria lobata (Willd.) Ohwi ssp. thomsonii (Benth.) Ohashi & Tateishi)為最優勢之種類；大多數的歸化豆科植物為原產於熱帶地區的草本，且偏好特定的棲地類型，如農地、河岸地、荒廢地及路邊。在土壤營養鹽部份，歸化豆科植物提高了局部的氮總量；另外，存在歸化豆科植物會顯著增加外來歸化植物之生物量及多樣性，但對於原生植物卻沒有增加或減少的趨勢。然而，若將歸化豆科植物從分析中移除，其存在與否對於其它外來歸化植物並沒有增加或減少的趨勢。
此外，分別探討歸化豆科植物種數最多的五種棲地，包括荒廢地、河岸、農地、墓地及路邊，其受衝擊程度與整體完全一致，即存在歸化豆科植物會顯著增加這五種棲地類型之外來歸化植物生物量及多樣性，但對於原生植物依舊沒有增加或減少的趨勢；但若將歸化豆科植物從分析中移除，其存在與否亦對於這五種棲地類型之其它外來歸化植物並沒有增加或減少的趨勢。
根據我們的結果，北臺灣地區之歸化豆科植物對於當地植物群落生物量與多樣性之衝擊幾乎接近中性；然而，我們仍需密切注意歸化豆科植物在臺灣中部與南部這些亞熱帶區域所造成之衝擊，一方面比較改變棲地物化因子之相同分類群在不同緯度間之衝擊性必定是個有趣的議題；另一方面，對於這些能改變棲地性質之分類群的了解能更佳透徹。

關鍵字

歸化植物 ； 入侵植物 ； 北臺灣 ； 重要值指數 ； 棲地類型 ； 衝擊 ； 改變棲地者 ； 豆科 ； 固氮作用 ； 生物承載量 ； 生物量 ； 生物多樣性

並列摘要

Chapter 1. Plant Invasion in north Taiwan: Insights from the Flora of Naturalized Alien Species

Regional naturalized flora with detailed information such as taxonomic composition, relative coverage, frequency, life form, and native areas and climates of naturalized species is important and available to further research. To generate better understanding of those characteristics of naturalized species, we developed and tested the following two hypotheses: (1) North Taiwan, as tropical / subtropical in low altitude and temperate in high altitude with diversified terrains and climate, is vulnerable to plant invasions from all over the world; and (2) the majority of successful naturalized species were introduced from areas with climates similar to those prevailing in north Taiwan. The field investigation was carried out in four counties in north Taiwan. By using 1km2 grid systems, one hundred of total grids were randomly selected as the sample areas. Five to ten square meters quadrates of each habitat type; furthermore, were investigated.
A total of 2,242 1-m2 quadrats and twelve habitat types were recorded. Plant species and coverage of all native and naturalized species were collected, and IVI values were calculated for each naturalized species for the summary of dominance. A total of 629 species belonging to 130 families and 409 genus were documented. In part of naturalized flora, there were about 80% dicotyledons in species number and 71% herbs in life form. Among these naturalized flora, Asteraceae, Poaceae, and Fabaceae were the most dominant families and Ipomoea was the most dominant genus according to their own species numbers. In addition, Bidens pilosa L. var. radiata Sch. was the dominant naturalized species according to the IVI value. In part of their origins, most naturalized species in north Taiwan were from America in area and tropical in climate.

Chapter 2. The Impacts of Naturalized Legumes on Plant Communities in north Taiwan

It has been shown that invasive plants usually impact local biodiversity by competitive exclusion, water depletion, microhabitat transformation, etc. Among these impacts, nitrogen-fixation is one of the most serious transform mechanisms invasive plant, such as legumes, may employ. Although the impacts of invasive habitat transformer have been discussed in few studies, comprehensive approaches on the impacts of local biodiversity and biomass upon community level have yet been conducted. My main purpose of this study was to estimate the impacts of naturalized legumes, notorious habitat transformers, on local biomass and biodiversity.
To generate better understanding of the impacts caused by naturalized legumes on local plant communities, we developed and tested the following hypotheses: (1) Presence of naturalized legumes is associated with relatively higher biomass and biodiversity; (2) Presence of naturalized legumes elevates soil nitrogen; (3) Naturalized legumes increase local biomass and biodiversity of both native and naturalized species; (4) The impacts of naturalized legumes on local communities are varied along habitat types. Furthermore, we also anticipated answering the following questions: (1) What are the dominant naturalized legumes in the study areas? ; (2) What are the favorite habitat types of naturalized legumes?
The field investigation was carried out in four counties in north Taiwan. By using 1km2 grid systems, one hundred of total grids were randomly selected as the sample areas. Five to ten square meters quadrates; furthermore, were investigated. A total of 2,242 1-km2 quadrats and twelve habitat types were recorded. Plant species and coverage of all native and naturalized species were collected, and IVI values were calculated for each naturalized legumes for the summary of dominance. Six biodiversity indices, including Shannon-Weaver (H’), Simpson (λ), Pielou evenness (J), Berger-Parker Dominance (BP) indices and species numbers (S), and total coverage (C) were summarized for further comparisons. In addition, soil samples were collected in pairs, presence and absence of naturalized legumes, to estimate the differences of available nitrogen.
A total of 629 species belonging to 130 families and 409 genus were documented. Among these species, 16 are naturalized legumes. Pueraria lobata (Willd.) Ohwi ssp. thomsonii (Benth.) Ohashi & Tateishi was the dominant species according to the IVI value, were recorded. Most of the naturalized legumes were herbs, from tropical areas, and preferred specific habitats, such as arable land, riparian, abandoned field, and roadside. In the part of soil nutrient, total nitrogen content was increased locally by naturalized legumes. Besides, local biomass and biodiversity of naturalized flora were increased significantly by naturalized legumes, but neither did native flora. However, the biomass and biodiversity of naturalized flora, excluding naturalized legumes, were not elevated on the enriched soils, either. Furthermore, separately for the habitat types, the results were consistently with overall condition that naturalized legumes significantly increased local biomass and biodiversity in those legume-preferred habitat types. But when naturalized legumes were excluded, there were no significant difference in separate habitats, either.
According to our results, the impacts of naturalized legumes on local communities, including biomass and biodiversity, in north Taiwan were nearly neutral. However, we should still pay attention to naturalized legumes whose impacts on central and south Taiwan. On the one hand, comparisons of impacts of the same taxon of habitat transformers among different latitudes would be an interested issue; on the other hand, the comprehensive study for habitat transformers would be further clarified.

並列關鍵字

Naturalized plant ； Invasive plant ； North Taiwan ； IVI value ； Habitat types ； Impact ； Habitat transformer ； Fabaceae ； Nitrogen fixation ； Carry capacity ； Biomass ； Biodiversity

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