硫磺噴氣孔植?生態與其指標植物個體生理生態之研究

Abstract

本文旨在研究大屯山火山群地區，火山作用造成植群生態的變動及植物之生理適應機制。因此吾人選定大磺嘴及四磺坪二個硫磺噴氣孔進行調查，記錄各植群植物之相對覆蓋度及分析土壤、水質和氣體三項環境因數，並將植群分佈與此三項環境因數進行分析。結果發現植群分佈與噴氣成份與溫泉水質雖無法成梯度關係，然而硫氣的噴發及硫磺的沉積與溫泉的侵蝕作用，不僅造成環境?處於擾動狀態，並造成土壤的酸化及高鹽離子堆積，因而?植物生長分佈之主要限制因數。 由DCA植群序列分析發現：(1)植群演替序列與土壤pH值及營養素皆呈顯著梯度相關，其中尤以pH值最具指標性，(2)初級演替及次級演替伴生出現該區。在火山作用直接影響下的植群，受土壤中強酸及高鹽離子的影響顯著，演替極?緩慢，因而保留初級演替的特色，且因微環境的差異出現藍球藻、火山葉蘚及台灣芒三種生育地條件不同的先驅植物，形成多源性之初級演替。同時在初級演替序列中，土壤高含硫量會造成植群停留在灌叢之亞極盛相，具硫磺泉植群(Solfataras vegetation)的特色。而在受自然崩塌及人?幹擾的地區，則呈現次級演替序列，並加速土壤化育，促使值群漸?該地區大氣候下自然演替之優勢植群，紅楠－山紅柿社會所取代。 硫磺噴氣孔的先驅植物中，以藍球藻的耐高溫及耐硫氣和火山葉蘚的耐強酸及耐高鹽害等特性最?特殊。並因兩者皆出現於世界其他之火山作用區，又普遍分佈大屯山群多處硫磺噴氣孔，故可視?火山指標植物。吾人發現藍球藻具嗜酸的生理特性，且藉由自行分泌有機酸得能存活於中性的培養基(BG-11)，並呈對數生長。另由生理實驗卻發現藍球藻雖然能在65℃自然的環境下存活，但在中性培養基(BG-11)中，無法忍耐41℃以上的溫度，而在37℃有最佳的生長速率，由此結果顯示中性的培氧基雖能容許藍球藻維持正常的生長，卻無法讓其表現其應有的溫度耐性。火山葉蘚在受到0.01 ppm以上的二氧化硫影響時，即會抑制光合作用之釋氧率，而處於0.07 ppm以上的濃度下，則完全無氧氣產生，且經15小時後仍無法恢復。顯見火山葉蘚不耐硫氣作用，其能存活於噴口裸地區，可能係因演化的過程中種間競爭壓力以及其對強酸及鹽害的耐性有關。

This thesis is to study the vegetation dynamic and physiological adaptation of two indicator plants in the area influenced by post-volcanism at Tatun Volcano group. Two solfataras of Tahuangtsui and Suhuangping were chosen as study sites. We studied plant community types and environmental factors, such as gas, water and soil released or influenced by solfataras. The distribution of plant communities does not correlate to gas and water gradients. However, the erosions caused by solfataras and hot springs have put the area under constant disturbance and resulted in high acidity and salinity in the soil. Both become the major limiting factors to the distribution of plants. Plant successional sera correlate significantly with pH value and nutrient gradients in the soil. In particular, pH value can be a indicator to plant successional sera. Also, primary successional sera is accompanied with secondary successional sera around the solfataras. At the place influenced directly by post-volcanism, the successional sequence was slow and maintained the features of early primary successsion because of high acidity and salinity. The heterogenety of microhabitats results in the features of polyoriginal primary succession, and different microhabitats were occupied by 3 different pioneers including Cyanidium caldarium, Jungermannia volcanicola and Miscanthus sinesis var. formosanus. The succession sera is arrested at a subclimatic stage (solfataras vegetation), due to the high sulfur content in soil, and is thus characterized by a special shrub community. At the place which is subjected to natural collapse or human disturbance, the secondary succession contiunes and promotes soil development. As a result, the primary vegetation would be replaced by the Perea thunbergii and Symplocos glauca community which is a dominant vegetation under the climatic condition in this area. Among the pioneer plant of solfataras, Cyanidium caldarium (Rodophyta) and Jungermannia volcanicola (Bryophyta) can be the indicator plants of solfataras vegetation because not only their special adapation but also their occurrence in the other solfataras of the world. We found this alga is acidophilic and can thrive in the BG-11 medium with pH value of 7 by secreting organic acid by itself. This eucaryotic alga can not survive the temperature greater than 41 C and the optimum temperature is 37 C in laboratory. The incapability of tolerance to high temperature shows that the physiological characteristic of the alga had changed in BG-11, even though it can live in the temperature as high-as 65 C under natural condition. The other indicator plant, Jungermannia volvanicola can not tolerant S2O in laboratory condition even at the concentration as low as 0.01 ppm. Furthermore, the alga which has been exposed to 0.07 ppm S2O for one hour treatment can't recover its photosynthesis after fifteen hours. Its restrictive distribution at bare land of solfataras may be the result of competition of species and of its tolerance to the high acidity and salinity after the long evolving processes.