| Emergy evaluation on ecological and economic systems of converting farmland into forest (grassland) project in loess hilly and gully areas |
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| DOI：10.7606/j.issn.1000-7601.2008.05.40 |
| Key Words: converting farmland into forest ecological and economic effects emergy analysis loess hilly and gully areas |
| Author Name | Affiliation | | DU Ying | College of Resources and Environment，Northwest A & F University, Yangling, Shaanxi 712100, China；Research Center of Recycle Agricultural Engineering and Technology of Shaanxi Province, Yangling, Shaanxi 712100， China | | YANG Gaihe | College of Agronomy，Northwest A & F University, Yangling, Shaanxi 712100, China；Research Center of Recycle Agricultural Engineering and Technology of Shaanxi Province, Yangling, Shaanxi 712100， China | | LIU Zhichao | College of Agronomy，Northwest A & F University, Yangling, Shaanxi 712100, China；Research Center of Recycle Agricultural Engineering and Technology of Shaanxi Province, Yangling, Shaanxi 712100， China | | FENG Yongzhong | College of Agronomy，Northwest A & F University, Yangling, Shaanxi 712100, China；Research Center of Recycle Agricultural Engineering and Technology of Shaanxi Province, Yangling, Shaanxi 712100， China |
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| Abstract: |
| Emergy analysis is one of the usually employed method to evaluate the input and output of ecosystem. Through analyzing dynamic changes of the emergy input and output before and after implementing the policy of Converting Farmland into Forest and Grassland in Ansai County located in the loess plateau area of Shaanxi Province, the ecological and economical effect of this policy is evaluated quantitatively. It is found that, influenced by the project of Converting Farmland into Forest and Grassland, both the yearly gross input and output emergy value show a increasing trend with only a little decrease in the initial period, and the organic emergy and the unrenewable environment and resources input shows a decreasing trend, which justifies that the Converting Farmland into Forest and Grassland project could have a positive effect on the maintenance of surface soil. In the total emergy output, the emergy output of planting and breading is the largest in quantitative amount. However, with the implementation of Converting Farmland to the Forest and Grassland, the emergy output of the forest begin to increase fast, and the structure of the ecosystem begin to develop in a multi-direction way. Among the main indexes of the ecosystem, emergy investment ratio and environment load ratio exhibit a trend of increasing first, then decreasing a little, and finally lasting increasing. In addition, both the emergy yield ratio and the emergy sustainable indices show a lasting increasing trend with only a little decreasing in the initial period, and the stability of the system exhibits an increasing trend. In conclusion, all those results show that after converting the farmland to the forest and grassland, the ecological pressure of the system begins to decrease, the durability begins to increase, the structure of the system becomes stable, and the system function gets harmonized. All these realize both the success in economical as well as ecological sense. |
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