气候变化条件下中国灌溉面积变化的产量效应

灌溉可以有效缓解气候变化对粮食生产的不利影响。采用中国不同区域2006-2019年实际灌溉用水量,对4个气候模式(GFDL-ESM2M,Had GEM2-ES,IPSL-CAM5-LR,MIROC5)驱动下的3种作物模型(GEPIC、PEPIC和LPJml)的灌溉用水量进行评估,优选模拟结果较好的前5个模式组合,分析RCP2.6和RCP6.0情景下,2021-2050年中国玉米、水稻、大豆和小麦产量变化,评估灌溉面积扩张的增产效应。结果显示:未来气候变化下,2021-2050年降水量的增加使得中国水稻和大豆以及北方地区玉米和小麦产量均呈现增长趋势,其中东北80%左右的地区和西北70%左右的地区玉米产量将提高0.2～0.8 t/hm~2,东北85%左右的地区水稻和大豆增产幅度分别超过1.0、0.5 t/hm~2,东北90%左右的地区和西北75%左右的地区小麦产量增幅分别介于1.0～2.0、0.5～1.0 t/hm~2之间。降水量的减少使得西南南部地区的玉米和小麦产量均下降0.2 t/hm~2左右。不同区域玉米和小麦的增产效应差异明显,由于北部地区光热条件较差、小麦基础产量较低,使得小麦灌溉增产潜力(1%～11%)以及增产效率((0.12±0.06)kg/m~3)均较高,北部地区小麦的灌溉面积扩张可有效应对气候变化的不利影响。

Yield effects of irrigated acreage change under climate change in China

Irrigation of crops can effectively increase yields and reduce inter-annual fluctuations in yields, thus mitigating the adverse effects of climate change on food production. However, there are significant differences in climate among different regions of China, and water and soil resources are not balanced among regions of China. The degree to which increasing irrigation in different regions can alleviate the impact of climate change is unknown. Therefore, in this study, the yield datasets under different climate scenarios published by ISIMIP were used to study the yield increase effect of irrigation expansion in different regions of China. Firstly, the irrigation water consumption of three crop models (GEPIC, PEFIC and LPJml) driven by four climate models (GFDL-ESM2M, HadGEM2-ES, IPSL-CAM5-LR, MIROC5) was evaluated using the actual irrigation water consumption in different regions of China from 2006 to 2019. Secondly, the first five model combinations with better simulation results were selected according to the skill scores S1 and S2. Then, the ensemble mean of the first five combinations with better performance was carried out to analyze the yield changes of maize, rice, soybean and wheat in China from 2021 to 2050 under RCP2.6 and RCP6.0 scenarios. Finally, the yield increase effect of irrigated area expansion under the assumption on the irrigation of rain-fed land in different areas was evaluated. The results showed that the increase of precipitation from 2021 to 2050 would increase the yield of rice and soybean, corn and wheat in northern China, among which about 80% of maize area in Northeast China and 70% of maize area in Northwest China would have the increasing of the maize yield by 0.2 - 0.8 t/hm2. About 85% of rice area and soybean area in Northeast and Northwest regions would have the increasing of the yield by 1.0 t/hm2 and 0.5 t/hm2, respectively. About 90% of wheat area in Northeast and 75% of wheat area in Northwest regions had the increasing of the by 1.0-2.0 t/hm2 and 0.5-1.0 t/hm2, respectively. The decrease of precipitation resulted in the decrease of maize and wheat yields by 0.2 t/hm2 in the 45% area of south southwest of China. Under the condition of expanding the irrigated area, the crop yield in Northwest and Southwest China would increase greatly during 2021-2050. Under RCP2.6 scenario, maize (northwest: 48%-60%; southwest: 7%-40%) was the highest, followed by soybean (northwest: 42%-62%; southwest: 2%-16%) and wheat (northwest: 11%-18%; southwest: 12%-33%); Under RCP6.0, maize (northwest: 43%-56%; southwest: 7%-39%) was the highest, followed by soybean (northwest: 38%-58%; southwest: 2%-23%) and wheat (northwest: 10%-18%; southwest: 15%-32%). The total yield of rice (soybean) in Northeast China increased significantly from 2021 to 2050. Under RCP2.6 and RCP6.0 scenarios, the total yield increased by 3%-10% and 3%-13% (7%-23% and 7%-23%), respectively. In terms of yield increase potential per unit irrigation amount, the expansion of irrigated area of wheat in Northeast China and North China during 2021 and 2050 had obvious yield increase benefit. Under RCP2.6 scenario, the wheat yield increase efficiency of irrigation was 0.18 and 0.12 kg/m3, respectively. The wheat yield increase efficiency under RCP6.0 scenario was 0.25 and 0.13 kg/m3, respectively. The irrigation area expansion of maize (rice) in central region (east) had obvious yield increase benefit. The maize (rice) yield increase efficiency under RCP2.6 and RCP6.0 scenarios was 0.1 and 0.09 kg/m3 (0.08 and 0.07 kg/m3), respectively. Therefore, the expansion of irrigated area for wheat in northern China can effectively cope with the adverse effects of climate change.