| Summary: | 博士 === 國立臺灣大學 === 生態學與演化生物學研究所 === 102 === This study was aimed to characterize the diversity, abundance, phylogeny, and stress physiology of indigenous soil algae at highly eroded badlands, including Dadu, Dakeng, and Hoyen Mountain situated in mid-Taiwan and to elucidate the feasibility of establishing biological soil crusts (BSCs). At Hoyen Mountain and Dadu, dominant soil algae were of chlorophytes including those genera of Bracteacoccus, Coccomyxa, Klebsormidium, and Koliella, while at Dakeng of cyanobacteria such as Leptolyngbya. The distribution of soil algae exhibited a strong dependency on environmental variables such as soil moisture, soil texture, and the vegetation type. For phylogenic analysis of soil algae, both the 16S rDNA and plastid 23S rRNA were used. The results showed that these algae belonged to an evolution complex. To study the physiology of water stress in soil algae, polyethylene glycol (PEG) was used as an inducer. As a response to PEG treatment, the intracellular proline levels were elevated, which was associated with increases in malondialdehye (MDA), pigment contents, and activities of antioxidant enzymes such as superoxide dismutase (SOD). As a result, the tolerance to water stress could be indicated by the intracellular levels of proline, SOD, and caroteniods. Moreover, to test the establishment of BSCs, L. boryana was used. The development of BSCs resulted from this organism would improve remarkably the biological and physiso-chemical properties of the soil environment. The establishment of BSCs could be differentiated into five stages, namely initial, mature, extended, contended, and declined. The time of establishment varied with environmental factors at the habitat. It was suggested that filamentous L. boryana may be a suitable pioneer organism for BSCs establishment and restoration of the disturbed environments.
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