Emergy synthesis of the agroecosystem in Yan'an area of China.

摘要

Emergy synthesis is an energy-based evaluation method useful for investigating agroecosystems in the context of ecology and economics owing to its ability to express different types of inputs on a common basis: the solar energy. In this article, emergy synthesis is used to analyze, in quantitative terms, the agroecosystem in the area of Yan'an, which coexists with a mineral exploitation region in the Loess Plateau of China. The analysis indicates that the emergy input supporting the agroecosystem totaled 1.26E+22 seJ/yr in 2006. On a percentage basis, renewable resources, nonrenewable resources, and purchased emergy accounted for, respectively, 36%, 31%, and 33% of the total emergy input. With 67% of its total emergy input derived from local resources (renewable and nonrenewable), the agroecosystem is indicative of a sustainable pattern of agricultural production. The environmental sustainability index for the agroecosystem was calculated to be 1.70. A comparative analysis indicates that Yan'an's agroecosystem is more sustainable than Chinese, Italian, and Japanese agriculture on a nationwide basis.