基于能值分析的土地可持续利用态势研究

本文应用能值分析的理论和方法，构建了基于能值的标定土地可持续利用态势的若干指数，如土地利用总能值投入产出比，土地利用工业能能值投入产出比，土地利用环境负载指数以及土地可持续利用指数。作为案例研究，作者利用上述指数对1978－1999年中车农业土地的可持续性进行判定。结果表明，尽管粮食产量或农业产值等经济指标为土地利用总能值投入产出比和工业能能值投入产出指数前期剧烈下降，后期趋于平缓；土地利用环境负载指数持续上升的态势说明，中国农用土地的环境压力逐渐增大，土地可持续利用指数在前期呈现上升趋势，至1985的达到最高，此后呈持续下降态势，近年趋于稳定。这表明，由过度使用化石能量引起的环境负面效应对农用土地生态系统的压力不断增大，若不遏制这种发展势头，中国农用土地生态系统的可持续性将得不到延存。

EMERGY-BASED ANALYSIS ON LAND SUSTAINABILITY

In recent years, many approaches have been used to quantitative evaluate the sustainability of regional land ecosystem, but most of them failed to explore the intrinsic characteristics of land sustainability due to imperfect evaluation paradigms. Emergy analysis (EMA), which was developed by H.T.Odum, is bold and broad-reaching approach to quantify the role of the environment in land use activities. According to the emergy analysis theory, the emergy flows that input the land ecosystem control the performance and behaviors of the system. So, the indices and ratios based on emergy flows can be calculated and employed to evaluate the sustainability of land ecosystem. In this paper, by transforming original statistic data into solar emergy we develop some emergy-based indices and ratios such as total emergy input-output ratio, industrial emergy input-output ratio, land environmental loading index, and emergy-based sustainable index of land use. As an empirical study, the indices and ratios are used to evaluate the cropland sustainability of China from 1978 to 1999. The results indicate that emergy analysis is an alternative approach for assessing the dynamic behaviors of land ecosystem. Each indices and ratios of cropland ecosystem in China exhibit different dynamic trends through the selected period (1978-1999). The total emergy input-output ratio shows a smooth transition while industrial emergy input-output ratio presents sharp decline. The stable increase of land environmental loading index and gentle decrease of emergy-based sustainable index suggest that there are huge environmental pressures and negative ecological impacts on cropland ecosystem in China.