退耕还林还草背景下黄土高原粮食生产系统可持续性的时空演变

粮食生产系统的可持续性事关国家粮食安全目标的实现,探究退耕还林还草背景下粮食生产系统的可持续性对准确评估生态安全和粮食安全之间的关系具有重要意义。基于2000、2010和2018年黄土高原县域粮食生产相关数据,构建粮食生产系统可持续性综合测度指标体系,对黄土高原粮食生产系统的可持续性进行综合分析;通过分析典型生态修复工程"退耕还林还草",阐明退耕对粮食生产系统可持续性的影响。结果表明：1）2018年黄土高原粮食生产系统的可持续性高于2000年,系统的可持续性在逐步增强;粮食生产系统可持续性由自然资源供给为主导,转变到以社会经济可持续发展为主导的阶段。2）2000-2010、2010-2018年间黄土高原粮食生产系统可持续性增长率分别达到31.03%和28.81%,因此,2000-2010年间是粮食生产系统可持续性大幅提升阶段。3）退耕背景下虽然耕地大幅减少（-33.48%）,但平均海拔和坡度也呈下降趋势（分别下降了20.3 m和0.88°）,土壤侵蚀模数由16.14 t/(hm2·a)降至9.34 t/(hm2·a),产水量和粮食生产潜力则年均增长5.09 mm/(km2·a)、53.75 kg/hm2。4）退耕背景下粮食生产系统的可持续性显著提升,工程的实施对六个分区粮食生产系统的可持续性都呈正向的促进作用;其中,土石山区粮食生产系统的可持续性指数由0.14增长至0.17,其受退耕的影响最大。退耕还林还草工程对易造成水土流失和土地沙化的生态脆弱地区实行退耕,虽减少了粮食生产的物质基础,但通过改变其空间分布格局,对耕地质量、耕地平均海拔和高度均产生影响,由此使得土壤侵蚀模数下降、水源涵养能力提高,有效地改善了生态环境,显著提升了粮食生产系统的可持续性。整体而言,退耕还林还草提升了粮食生产系统的可持续性,生态安全对粮食安全存在着正向的促进作用。

Spatiotemporal changes of the sustainability of grain production system in the Loess Plateau based on Grain for Green Project

Abstract: Sustainability in the grain production system is closely related to the entire food processing and supply chain for the national food security. It is a high demand to explore the sustainability of the Grain for Green Project for the grain production system, in order to accurately assess the relationship between ecological and food security. In this study, a comprehensive evaluation index system was constructed for the sustainability of the grain production system using the relevant data of grain production in various counties and districts of the Loess Plateau in 2000, 2010, and 2018. A typical ecological restoration project "Grain for Green" was then analyzed to clarify the impact of returning farmland on the sustainability of the grain production system. The results show that: 1) The sustainability of the grain production system on the Loess Plateau in 2018 was higher than that in 2000, indicating a gradually increasing trend. Specifically, the sustainability of the grain production system was dominated by the supply of natural resources, and then shifted to a stage dominated by the sustainable socio-economic development. 2) There were small differences in the sustainability of grain production systems on the Loess Plateau, most of which were in the low-to-medium sustainability level in 2000. Furthermore, the sustainable growth rate of the grain production system on the Loess Plateau reached 31.03% and 28.81%, respectively, from 2000 to 2010 and from 2010 to 2018. Therefore, the period from 2000 to 2010 presented a substantial improvement in the sustainability of the grain production system. 3) Although the cultivated land was greatly reduced (-33.48%) under the background of the Grain for Green Project, the average altitude and slope also showed a downward trend (decreased by 20.3 m and 0.88°, respectively), and the soil erosion modulus decreased from 16.14 to 9.34 t/(hm2·a), while the water volume and grain production potential increased by 5.09 mm/km2 and 53.75 kg/(hm2·a) annually, respectively. 4) The sustainability of the grain production system exhibited significant improvement under the background of the Grain for Green Project, indicating a positive effect of project implementation on the sustainability of the grain production system in the six sub-regions. More importantly, there was an increase from 0.14 to 0.17 in the sustainability index of the grain production system in the rocky mountainous area, which was the most affected by the project of the Grain for Green. Correspondingly, the Grain for Green Project can return the farmland to the ecologically fragile areas, particularly of soil erosion and land desertification. Therefore, the spatial distribution pattern greatly varied in the quality, average altitude, and height of cultivated land, indicating the reduced material supply of food production. As a result, the soil erosion modulus was reduced to effectively improve the water conservation capacity, the ecological environment, and the sustainability of the grain production system. On the whole, the Grain for Green Project has promoted the sustainability of the grain production system for the better ecological restoration of national food security.