College of Resources and Environmental Sciences, China Agricultural University, No. 2 Yuanmingyuan West Rd., Haidian District, Beijing, 100193, China; School of Natural Resources, University of Nebraska-Lincoln, 3310 Holdrege Street, Lincoln, NE, 68583, USA.
Glob Chang Biol. 2013 Nov;19(11):3481-92. doi: 10.1111/gcb.12324. Epub 2013 Aug 18.
Northeast China (NEC) accounts for about 30% of the nation's maize production in China. In the past three decades, maize yields in NEC have increased under changes in climate, cultivar selection and crop management. It is important to investigate the contribution of these changing factors to the historical yield increases to improve our understanding of how we can ensure increased yields in the future. In this study, we use phenology observations at six sites from 1981 to 2007 to detect trends in sowing dates and length of maize growing period, and then combine these observations with in situ temperature data to determine the trends of thermal time in the maize growing period, as a measure of changes in maize cultivars. The area in the vicinity of these six sites accounts for 30% of NEC's total maize production. The agricultural production systems simulator, APSIM-Maize model, was used to separate the impacts of changes in climate, sowing dates and thermal time requirements on maize phenology and yields. In NEC, sowing dates trended earlier in four of six sites and maturity dates trended later by 4-21 days. Therefore, the period from sowing to maturity ranged from 2 to 38 days longer in 2007 than it was in 1981. Our results indicate that climate trends alone would have led to a negative impact on maize. However, results from the adaptation assessments indicate that earlier sowing dates increased yields by up to 4%, and adoption of longer season cultivars caused a substantial increase in yield ranging from 13% to 38% over the past 27 years. Therefore, earlier sowing dates and introduction of cultivars with higher thermal time requirements in NEC have overcome the negative effects of climate change and turned what would have otherwise been a loss into a significant increase in maize yield.
中国东北地区（NEC）的玉米产量约占全国的 30%。在过去的三十年中，由于气候、品种选择和作物管理的变化，NEC 的玉米产量有所增加。研究这些变化因素对历史产量增长的贡献对于提高我们对未来如何确保产量增加的认识非常重要。在这项研究中，我们使用了 1981 年至 2007 年六个地点的物候观测数据来检测播种日期和玉米生长周期长度的趋势，然后将这些观测结果与当地温度数据相结合，以确定玉米生长周期中的热量时间趋势，作为玉米品种变化的衡量标准。这六个地点附近的区域占 NEC 玉米总产量的 30%。使用农业生产系统模拟器 APSIM-Maize 模型，将气候变化、播种日期和热时间需求的变化对玉米物候和产量的影响分开。在 NEC，六个地点中有四个的播种日期呈提前趋势，成熟日期平均延迟了 4-21 天。因此，与 1981 年相比，2007 年从播种到成熟的时间延长了 2 到 38 天。我们的研究结果表明，仅气候趋势就会对玉米产生负面影响。然而，适应评估的结果表明，更早的播种日期使产量增加了 4%，而采用更长季节的品种使产量在过去 27 年中增加了 13%至 38%。因此，在 NEC 中更早的播种日期和更高热时间需求品种的引入克服了气候变化的负面影响，将原本可能导致的损失转化为玉米产量的显著增加。
