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作 者 ：王继军*,郭满才,姜志德,苏鑫,李慧,李奇睿

期 刊 ：生态学报 2010年 30卷 9期 页码：2371~2378

关键词：农业生态经济系统；耦合过程；模型；临界点；纸坊沟流域；

Keywords:agricultural ecological-economic system, coupled process, model, critical point, Zhifanggou Watershed,

摘 要 ：基于“一般系统论中系统演化”的思想、“Thornes关于植被和土壤侵蚀耦合模型”等思路，构建了农业生态经济系统耦合过程的基础模型和扩展模型。通过该模型能够揭示农业“生态—经济”的互动过程、确定农业经济系统影响生态系统的临界点，这对于开发利用农业资源、制定农业生态经济系统可持续发展方案具有重要的现实意义。以纸坊沟流域20余年农业生态经济系统演变资料为基础，借鉴已有研究结果，通过对“模型”参数的计算，建立了反映纸坊沟流域不同情境下农业生态经济系统耦合过程模型，结果表明：按照农业生态经济系统现状演变轨迹，农业生态系统自我调节的临界点为en(t)=1.22×el(t)；如果继续完善系统循环，强化“林草资源-畜牧业”链网，在生态系统阈值范围内可增强经济系统功能；如果停止“退耕”而出现复垦，生态系统自我调节的临界点变为en(t)=0.69×el(t)，单位生态系统功能减弱。为此，必须稳定退耕还林工程，促进农业资源合理、高效利用，加速产业优化升级，这样方能实现农业生态经济系统健康、持续发展。

Abstract:Basic and extended coupled process models of an agricultural ecological-economic system were set up using system evolution theory and Thames′ coupled model of vegetation and soil erosion. The model revealed the interactive process of agricultural ecological-economics and showed the critical point at which the agricultural economic system impacted the ecological system. This has important practical significance for the utilization of agricultural resources and the development of sustainable programs for the agricultural ecological-economic system. Based on more than 20 years of system evolution information from the Zhifanggou Watershed of the Loess Plateau, key parameters (k1,k2,k3,k4) which revealed the direction and intensity of interaction between the agriculture-economic and ecological systems as well as adjustment parameters (α1,α2) which indicated the evolutionary track transformation of the economic and ecological systems resulting from significant behavioral processes were calculated. Then the coupling process model was established to reflect the coupling process between the agriculture-economic and ecological systems in different situations. The results showed that the evolutionary speed of the agricultural-ecological system was negatively related to the state of the economic system but positively related to the state of the ecological system. There was also a positive relationship between the evolutionary speed of the agricultural-economic system and the state of both the agricultural economic and ecological systems. The critical point of self-regulation for the current evolutionary track of the agricultural ecological-economic system in the Zhifanggou Watershed was en(t)=1.22×el(t). At this critical point, the evolutionary speed of the economic system was 0.051×el(t). which means that under the conditions of the self-balanced ecological system, the economic system reached its greatest evolutionary speed of 0.051×el(t). If the systemic circulation and the “forest and pasture resources-animal husbandry” chain network continue to be perfected and strengthened, then the economic system function could be enhanced within the framework of the threshold of the ecological system. According to the “Rotation Pasture and Barn Feeding” management systems, if 300 sheep were raised during the early days in the Zhifanggou Watershed under the potential grazing capacity of 500 sheep, then the calculated values would be 0.557 for α1 and 0 for α2. There was no significant effect on the critical point of self-regulation for the agricultural ecological-economic system, and the maximum allowable evolutionary speed of the economic system was 0.073×el(t). If the “Grain for Green Project ” were stopped and the reclamation was emerged, the function of economic and ecological systems would both fall. We hypothesized that if the “Grain for Green Project” were cancelled, the conditions for farmland in the Zhifanggou Watershed were slightly better than conditions in 1999, the calculated values would be 0.1 for α1 and -0.386 for α2. The critical point of the ecosystem self-adjustment changed to en(t)=0.69×el(t), the maximum allowable evolutionary rate of the economic system changed to 0.047×el(t), and the unit ecosystem function was weakened. To this end, we should stabilize the “Grain for Green Project”, promote the efficient utilization of agricultural resources, and upgrade industries in the region. Only in this way, can the agricultural ecological-economic system achieve healthy and sustainable development.

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