摘要:合理的种植结构是实现区域水资源及土地资源优化配置的基础。针对白洋淀上游水资源紧缺、种植结构不合理等问题，结合当前主要作物种植结构现状，本研究以作物种植面积为优化变量，以水资源、土地资源、社会需求等为约束条件，以经济效益、生态效益最大及总灌溉耗水量最小为目标，构建基于非支配排序遗传算法（NSGA-Ⅱ）的作物种植结构多目标调整模型，并提出了针对白洋淀上游平原区、山区等不同水资源限制和农业机械化程度情景下的种植结构调整优化方案。研究结果表明，在平原区现状机械化水平下，在不限制用水的情景下，可以通过调减一年两作的种植面积，增加蔬菜和绿豆-鲜食玉米等的种植面积，达到提高经济效益12.6%的目的，而生态效益和节水效益都有所降低。在限水情景下，小麦-玉米调减比例增加，调增绿豆-鲜食玉米、春季甘薯、蔬菜和果蔬的面积，实现经济效益和节水效益的提高；而要达到节水20%的目标，所有作物的种植面积都要缩减，高耗水种植制度小麦-玉米种植面积缩减比例达21.5%，同时经济效益和生态效益都下降。在未来提高机械化水平的情景下，调整优化后的经济效益相比现状机械化水平提高或下降减少。在山区所有情景下，小麦-玉米种植面积随着对水分限制水平（不限水—小于现状水资源—节水20%）的增加调减比例增加，同时增加果树的种植面积。在山区可以通过种植结构的调整达到既节水20%，同时经济效益提高的目标，这是平原区所不能达到的。总之，无论是平原区还是山区，均是在不限水情景下优化后的经济效益、生态效益相对较高，而节水越多，优化后的经济效益、生态效益增幅越小、降幅越大。并且在平原区如果在节水要求不高的情景下应适当增加蔬菜面积，减少粮食种植面积；在节水要求高的情景下应削减所有作物包括水果、蔬菜的种植面积，在山区应该适当削减粮食种植面积，扩大果树的种植面积。该研究不仅可为研究区未来作物种植结构调整提供决策依据，也为在类似地区种植结构调整和水资源优化管理提供了新的情景参考。
关键词:NSGA-Ⅱ算法/
种植结构/
经济效益/
生态效益/
水资源优化
Abstract:Reasonable planting structures are the basis of the optimal allocation of regional water and land resources. The upstream region of Baiyangdian Lake suffers from the perils of water shortage and an unreasonable planting structure. On the base of the current status of the main crop planting structure, this study considered the crop planting area as optimization variable, the water resources, land resources, and social needs as the constraints, while seeking to maximize the economic and ecological benefits and to minimize the irrigation water consumption based on the non-dominated sorting genetic algorithm (NSGA-Ⅱ) of the crop planting structure adjustment model. This study also proposed the planting structure optimization schemes under different scenarios of various water restrictions and agricultural mechanization levels in the mountain area and plain area of the upstream of Baiyangdian Lake. The results showed that, at the current status of mechanization level, the area of the rotations of two crops in a year scaled down, while vegetables and mung beans-fresh maize areas increased, the economic benefits should increase 12.6%, and ecological and water-saving benefits decreased under the no-restricted irrigation water; while wheat-maize, mung beans-fresh maize, spring sweet potato, vegetables and fruits areas increased under restricted irrigation water inducing increased economic and water-saving benefits. In the 20% water-saving scenario, almost all crop areas would be scaled down, including vegetables, area of wheat-maize decreased 21.5%, and economic and ecological benefits decreased. In the scenario without water limitation, the optimized economic benefit increased the most, the ecological benefit decrease the least, water consumption increased, and the grain yield decreased the least. However, in the scenario of 20% water saving, the economic and ecological benefits and grain yield decreased. Under current and future mechanization levels, the fruit tree area increased under different water restriction scenarios. With no-water limitation, the economic and ecological benefits maximally improved after optimization, and water use and grain yield maximally decrease. Under the 20% water-saving scenario, the economic benefit increased the least, the ecological benefit decreased, and grain yield decreased the most. These results indicate that the current and future mechanization scenarios are not limited by water in the plain or mountainous areas, and the optimized economic and ecological benefits are relatively high. Moreover, in the plain areas with low water-saving requirements, the vegetable planting area should be increased, and the grain planting area should be reduced. In areas with high water-saving requirements, the planting area of all crops, including fruits and vegetables, should be reduced. In the mountainous areas, the grain planting area should be reduced, and the fruit tree planting area should be expanded. This study provides a decision basis for future regional planting structure adjustment. Past adjustments in the planting structure, with more adjustments according to different crop types, tended to ignore adjustments in the different cropping systems or to consider the fixed number of years or different climate scenarios. This paper proposed different scenarios of mechanization and water limitations and highlighted the optimization results under different scenarios for similar areas after adjustment in the planting structure.
Key words:Non-dominated sorting genetic algorithm (NSGA-Ⅱ)/
Planting structure/
Economic benefits/
Ecological benefits/
Optimization of water resources
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