黄土高原-青藏高原过渡带农户生产系统的能值分析——以通渭-渭源-夏河样带为例

通渭-渭源-夏河样带位于黄土高原向青藏高原过渡的生态区,是我国典型农牧交错带。长期以来,不合理的农业生产结构带来生态、经济等一系列问题,制约了该地区草地农业的持续发展。为此,从能值角度分析区域农业生产结构,可为农(牧)户决策提供理论依据,为优化区域农业生产结构提供科学依据。收集研究区农户作物和家畜生产的投入-产出数据,用能值方法分析农户生产系统结构特征、农户生产决策行为及生产系统耦合作用,用结构方程模型(SEM)分析农户生产系统能量的组分间流动。研究发现,随海拔增高,农户作物生产活动减少,作物总产出能值递减;尽管作物生产主要投入和产出要素相同,但同一作物不同地点的同一要素投入、产出能值和能值收益率均存在显著差异(P0.05);同一地点不同作物的同一要素投入、产出能值和能值收益率均差异显著(P0.05);作物生产投入要素中,有机肥能值在通渭和渭源均有较高贡献;作物投入和产出能值的农户生产决策阈值自东向西递减,在能值投入初始增加时,夏河农户作物生产规模扩增最为迅速。家畜养殖规模、能值投入和产出自东向西递增;通渭和渭源,小麦秸秆和苜蓿作为中间投入,能值贡献率达到80%;夏河家畜生产投入要素中,补饲粮食能值贡献率高达90%;家畜投入和产出能值的农户生产决策阈值点自东向西递增;能值收益率随耦合度的增加呈指数上升,通渭和渭源能值收益率的增加速度,随耦合度的增加趋于缓慢,而夏河能值收益率增速随耦合度的增加而上升。调整作物生产内部粮、经、饲产品比例结构,加强作物生产与家畜生产耦合作用,优化天然草地利用方式,实现生态效益最大化;阈值点调控农户生产决策行为,实现该区域农业生产结构优化。

Emergy analysis of farmer producing system in the transitional zone of Qinghai-Tibet Plateau on Loess Plateau: Tongwei-Weiyuan-Xiahe Transect as an Example

The Tongwei-Weiyuan-Xiahe transect zone is located in the ecological zone of transition ranging form the Loess Plateau to the Qinghai-Tibet Plateau. It is a typical agri-pastoral transitional zone of the Northern China. For a long time, ecological and economic problems caused by the inappropriate agricultural production structure have severely restricted the sustainable development of grassland agriculture in this region. From the perspective of emergy, this research aims to (1) provide a new data support and theoretical basis for the adjustment of local agricultural production structure, policy formulation, and agricultural (pastoral) household decision-making in this area and (2) provide a scientific basis for the optimization of regional agricultural production structure. Input-output data of crop production and livestock production of households in the study area have been collected; the emergy value method has been adopted to analyze the input-output structure characteristics of crop production and livestock production, the production decision-making behavior of farmers, and the coupling effect of production systems. By applying the structural equation model (SEM), this research analyzed the energy conversion between components of production systems. It is demonstrated by this research that with the increase of altitude, crop production activities of farmers would decrease and the total output value of crops would also decrease. Although the main inputs and output factors of crop production are the same, the input emergy, output emergy, and emergy yield ratio of the same factor in different parts of the same crop can be varied. Significant differences can be seen from the input, output emergy value, and emergy yield ratio of the same factor at the same location of different crops (P < 0.05). In the input factors of crop production, the emergy value of organic fertilizer made significant contribution in Tongwei and Weiyuan. Agricultural production decision thresholds for crop input and output emergy values decreased from the east to the west, while the crop production scale in Xiahe expanded most rapidly when the initial input of emergy increased. Animal husbandry scale, emergy input, and output of animal production increased from the east to the west. In Tongwei and Weiyuan, wheat straw and alfalfa, as intermediate inputs, achieved 80% emergy contribution rate. In Xiahe, with animal production input factors, the contribution rate of supplement grain emergy value was as high as 90%, while the farm production decision threshold of livestock input and output emergy increased from the east to the west. The emergy yield ratio increased exponentially with the increase of the coupling degree. The speed of emergy yield ratio in both Tongwei and Weiyuan tended to decrease with the increase of the coupling degree, whereas, the speed of emergy yield ratio in Xiahe increased with the increase of the coupling degree. Adjusting the internal proportion of grain, cash crop, and feed products in crop production can strengthen the coupling effect between crop production and livestock production. Thus, optimizing the use of natural grassland and maximizing ecological benefits can be achieved. The threshold point can be used to regulate the production decision-making behavior of farmers and optimize the agricultural production structure in the region.