Understanding long-term (1982-2013) patterns and trends in winter wheat spring green-up date over the North China Plain
Understanding long-term (1982-2013) patterns and trends in winter wheat spring green-up date over the North China Plain
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DOI：
10.1016/j.jag.2017.01.008
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发表时间：
2017-05
期刊：
影响因子：
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通讯作者：
Sisi Wang;X. Mo;Zheng-jia Liu;M. Baig;Wenfeng Chi
中科院分区：
文献类型：
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作者：
Sisi Wang;X. Mo;Zheng-jia Liu;M. Baig;Wenfeng Chi
监测春季催熟期（GUD）对作物管理和粮食安全越来越重要。然而，大多数基于卫星的GUD模型在应用于农田时具有高度的不确定性。本文利用全球清查模型与制图研究（GIMMS3g NDVI）的第三代归一化植被指数，采用改进的GUD算法提取华北平原32 a（1982-2013）冬小麦农田的GUD数据。综合分析了季前气候条件和土壤水分条件对土壤需水量的时空变化规律。结果表明，与MCD12Q2物候产品相比，改进算法的GUD具有更高的相关系数（r = 0.44, p < 0.01）、更低的均方根误差（22天）和偏差（16天）。在空间上，从西南方向（小于60天）到东北方向（大于90天），gd呈增加趋势，与气温和降水的空间减少相对应。在NCP上，大多数冬小麦地区（78%）的谷氨酸脱氮量提前，其中37.8%的地区显著提前（p < 0.05）。古德温在高海拔地区和沿海地区发生的时间晚于内陆地区。年际尺度上，平均GUD从1980年代的76.9天（1982-1989年平均值）提前到1990年代的73.2天（1991-1999年平均值），2000年以后的70.3天（2000 - 2013年平均值），平均提前了1.8天/ 10年（r = 0.35, p < 0.05）。尽管谷氨酸耗散主要受季前温度控制，但我们的研究结果表明，季前土壤湿度对谷氨酸耗散的影响也应考虑在内。改进的GUD算法和基于卫星的长期GUD数据有助于改善GUD在陆地生态系统模型中的代表性，提高作物管理效率。
Monitoring the spring green-up date (GUD) has grown in importance for crop management and food security. However, most satellite-based GUD models are associated with a high degree of uncertainty when applied to croplands. In this study, we introduced an improved GUD algorithm to extract GUD data for 32 years (1982–2013) for the winter wheat croplands on the North China Plain (NCP), using the third-generation normalized difference vegetation index form Global Inventory Modeling and Mapping Studies (GIMMS3g NDVI). The spatial and temporal variations in GUD with the effects of the pre-season climate and soil moisture conditions on GUD were comprehensively investigated. Our results showed that a higher correlation coefficient (r = 0.44, p < 0.01) and lower root mean square error (22 days) and bias (16 days) were observed in GUD from the improved algorithm relative to GUD from the MCD12Q2 phenology product. In spatial terms, GUD increased from the southwest (less than day of year (DOY) 60) to the northeast (more than DOY 90) of the NCP, which corresponded to spatial reductions in temperature and precipitation. GUD advanced in most (78%) of the winter wheat area on the NCP, with significant advances in 37.8% of the area (p < 0.05). GUD occurred later at high altitudes and in coastal areas than in inland areas. At the interannual scale, the average GUD advanced from DOY 76.9 in the 1980s (average 1982–1989) to DOY 73.2 in the 1990s (average 1991–1999), and to DOY 70.3 after 2000 (average 2000–2013), indicating an average advance of 1.8 days/decade (r = 0.35, p < 0.05). Although GUD is mainly controlled by the pre-season temperature, our findings underline that the effect of the pre-season soil moisture on GUD should also be considered. The improved GUD algorithm and satellite-based long-term GUD data are helpful for improving the representation of GUD in terrestrial ecosystem models and enhancing crop management efficiency.