Emergy Evaluation of Agro-ecosystem of Shiyang River Basin,Northwestern China

中国西北地区石羊河流域农业生态系统能值评价(英文)

This paper presents an ecological analysis of agricultural systems in arid region of Northwestern China. Emergy analysis, a method for environmental accounting developed by H.T. Odum in the Eighties, is appropriate for this task because of its ability to transform different types of inputs to a common form （solar emergy） in order to allow scientific and objective comparisons across different period and regions. Taking Liangzhou and Minqin oases, located in the middle and lower reaches of the Shiyang River basin in Gansu province as a case study, the detailed structure of the agricultural process, input/output and emergy indicators of the systems are examined and compared for the years 1986 and 2000. Both the total emergy input and the total yield increased in the two oases. In Liangzhou Oasis the emergy of livestock production exceeded the traditional crop production, which still is the dominant production in Minqin Oasis. The emergy investment ratio, EIR, although increased in the investigated period, was less than 0.5 in both Liangzhou and Minqin oases, indicating that purchased materials and services were less than half the value of indigenous emergy sources exploited. As a consequence, the emergy yield ratio, EYR, was very high in both Liangzhou and Minqin oases. However, the increasing environmental loading ratio, ELR, and the decreasing environmental sustainability index, ESI, in the two oases illustrate a weakening sustainability of the two agro-ecosystems, and this tendency was more evident in the downstream Minqin Oasis, calling for more attention to the environmental degradation in the region.

通过能值方法分析了石羊河流域农业生态系统的资源环境基础和经济特征。结果表明,石羊河流域中下游凉州区和民勤绿洲的能值总投入呈降低趋势,能值投资率都偏高,生产成本较大;能值产出率低,对购买能值的利用效率不高;但能值自给率有所提高;环境载荷率高,农业生态环境所受压力较大,系统可持续发展指标表明两个绿洲经济系统极为不发达,属于消费型经济系统,并且人均可用能值和能值密度都呈降低趋势。