| Summary: | 博士 === 國立中興大學 === 水土保持學系所 === 101 === Comparing to the scale of time, the succession of ecosystem seems to be long, slow and unobvious for human beings. The changes of environment that are tiny but wide spread could lead to an enormous catastrophe. In classic approaches, soil forming and delivery process of watershed can be estimated and simulated by USLE and its modified version, RUSLE. In long-term concepts, the annAGNPS combined with GIS is also used as an efficient tool to simulate runoff. Unfortunately, the influences of climate changes and extreme weather events to soil and water resources in watershed are far beyond the capability of analysis technique applied for normal situations nowadays. To overcome rapid changes and analyze impacts, a wider foresight for environment changing tendency is needed.
Environmental index can be applied, like a physical checkup and can also be observed and examined from the whole system to the detail inside via many kinds of technique. The purpose of this research is to integrate well-developed technologies and extract the key environmental index with impact sensitivity. Applications of the key index on environment protection is then verified to establish operable, technical and theoretical strategy frames of hotspot in upstream watershed.
The first phase of this study is discussing and finding the patterns of mountain areas changes under the condition of global climate change via environmental index. Second, with the information of environment and ecosystem changes, the method of extracting hot spots in upstream watersheds of these changes via environmental index will be discussed. The study selects the Yi-Nian bridge watershed in Xueshan to be study area. Integrating satellite images and field investigations finds out the change of vegetation coverage and the distribution of water resource to extract the hot spots from watershed. The relation between erosion and management of the impact from human activities could be examined by Terrestrial Substance Index.
The result reveals that the environment condition of ecosystem at alpine area could be indicated by the variation of NDVI and NDWI. Green deterioration rate, which can be extract from NDVI after linear transformation process, has a linear negative relationship between carbon stock which can be extract from Land use data and vegetation group. This relationship shows that green deterioration can be an environmental index of watershed carbon stock, and carbon stock can indicate the variation of watershed land use. Changes of averages and variations of NDVI and NDWI in different seasons can reveal the changes of vegetation cover and moisture content. Thus the spatial and time characteristics of ecosystem in alpine area under climate change can be evaluated efficiently to find environment influence sensitive area. On the other hand, the relationship between soil erosion in watershed and human activities can be examined by land material delivery index. Moreover, it also discovers that the specific snow accumulation of the cirque in mountain area could relief influences to sensitive regions of environment from climate change.
This research recommends adapting global climate change for the strategy of soil and water conservation through monitoring ecotone in upstream area as priority, monitoring the variation and move of water resources, managing the water resources accumulation area with watershed topography conditions such as snow and water accumulation spot and extending the base flow afflux during arid season to eliminate water repellent phenomenon after fire burn, part of grass roots need to be removed to increase water infiltration if necessary. For management, the buffer of river should be established base on laws to release impacts come from land area material, moreover, farming-forbidden zone might be established to increase the area of forest. The result shows that besides the significant to watershed environment, vegetation and water index are operable, assessable and examinable. For soil and water resource conservation strategy made by watershed management authorities, these indexes are also universal, easy to apply and can prevent irreversible environment decaying inder the condition of climate change. The final conclusion of this study shows that the research method is operable, evaluable and testable besides vegetation and water index with characteristics significant of watersheds. Simultaneously, the conclusion can be applied easily, economically and theoretically by watershed management authorities as soil and water conservation strategy. Moreover, all of the achievements in this study can be references of conservation works at upstream watersheds in alpine region to prevent irreversible decaying of envirionment.
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