为了分析未来时期(2020—2099年)长江中下游区域气象干旱演变特征,选取跨行业影响模式比较计划(ISIMIP)的4个全球气候模式,基于不同代表性浓度路径(RCP)的排放情景(RCP-2.6、RCP-6.0和RCP-8.5),分别计算了标准化降水指数(SPI)和标准化蒸散发指数(SPEI),探讨了两种指数对研究区气象干旱的刻画能力,分析了研究区未来气象干旱变化规律。研究结果表明:未来时期SPI整体呈增加趋势,汉江流域和洞庭湖水系西北区域增加幅度较大,说明该区域干旱减缓趋势明显;SPEI呈显著减小趋势,且随着排放浓度的增加,减小幅度逐渐增加,洞庭湖水系和鄱阳湖水系东南区域减小趋势较大,说明该区域未来时期干旱增加趋势明显;不同情景下SPI减小的区域SPEI也呈减小趋势且减小幅度更大;研究区SPI与SPEI的相关性从北到南、从西到东逐渐增强;SPI与SPEI的整体相关性随着排放浓度的增加逐渐减弱。研究成果有助于预估未来长江中下游区域干旱发生演变规律。

To reveal the change trend and evolution patterns of future drought during 2020-2099 in the middle and lower reaches of the Yangtze River Basin, we calculated the Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) based on precipitation and potential evapotranspiration (PET) data from 4 Global Climate Models (GCMs) under RCP-2.6,RCP-6.0 and RCP-8.5 scenarios, which are derived from Inter-Sectoral Impact Model Inter-comparison Project (ISIMIP). We also looked into the performance of SPI and SPEI in detecting and depicting drought features. Results unveil an overall climbing trend of SPI in future, with the Hanjiang River basin and the northwest Dongting Lake network witnessing a surge, which means that drought in these regions will relieve obviously in the future. SPEI shows a reducing trend in most regions under all scenarios, and such reduction escalates with the rising of emission concentration; particularly, in the southeast of Dongting Lake network and Poyang Lake network,the reductions are larger than that in other regions,implying a notable drying trend in future.SPEI drops greater in regions where SPI declined under all scenarios.The correlation between SPI and SPEI gradually intensifies from north to south and from west to east in the study area.The overall correlation between SPI and SPEI weakens gradually from RCP-2.6,to RCP-6.0 and to RCP-8.5 scenario.

基于1960~2012年逐月降水资料,选取标准化降水指数（SPI）为干旱衡量指标,将SPI1与水稻各生长阶段（Growth Period of Rice,GPR）相结合,研究西南地区近53 a来整体和水稻（Oryza sativa）4个生长阶段的干旱时空演变特征。结果表明：整体上,西南地区历年干旱站次比均高于50%,全域性干旱特征显著。水稻不同生长阶段干旱时空分布特征差异显著。① GPR1和GPR2阶段以全域性干旱为主,GPR3和GPR4阶段则呈现局域性干旱>区域性干旱>全域性干旱的特征;② 生长阶段内干旱连续性特征明显,尤其是GPR2 阶段,易发生周期为2~6 a的全域性干旱和区域性干旱。③ 轻旱高值区呈现由东北向西南转移的趋势;中旱高发区呈现出明显的从北部向南部移动的趋势;重旱高发区各阶段空间分布差异较大。④ 水稻在GPR1和GPR2阶段主要受轻旱和中旱影响;GPR3和GPR4阶段重旱发生频率上升,影响范围增大。

Based on monthly precipitation data from 1960 to 2012, Standard Precipitation Index with 1 month time scale (SPI1) is calculated. We investigate the spatial and temporal variation characteristics of agriculture drought based SPI1 index and four growth stages of rice in the Southwest China. Results show that: 1) Overall, the drought station ratio for each year from 1960 to 2012 in the southwest is high and above 50%, presenting whole drought characteristic. 2) The temporal and spatial characteristics of agriculture drought during rice growth stage are different. ① From 1960 to 2012, GPR1 and GPR2 phases are dominated by whole drought. GPR3 and GPR4 phases show the distribution of the localized drought > regional drought >whole drought. ② The continuity drought characteristics during each growth stage of rice are evident. Especially in GPR2, it appears the whole drought and regional drought with the period of 2-6 years. ③ The area with high drought occurrence frequency for three type of drought has shown spatial shift characteristic during different growth stage. The area with high occurring probability of mild drought has transfer from northeast to southwest trend. The region with high occurring probability of moderate drought transferred from the north to the south. The region with high occurring probability of severe drought the spatial distribution of each stage is quite different. ④ In the GPR1 and GPR2 phases, rice is mainly affected by mild drought and moderate drought. In GPR3 and GPR4, severe drought occurrence frequency increases.

In this study, the effects of the water stress on rice root and yield were studied. Gui liang you 2 was taken as material and polyethylene glycol(PEG—6000)was used to simulate the different degrees of water stress. After dealt with water stress for 16 days at tillering stage and heading stage respectively, the material was supplied with nutrition as normal. The morphological traits and activity and dry matter of rice root were measured after the period of re-watering, and grain yield was measured during the mature period. The results showed that:The root activity could be enhanced owning to moderate water stress at tillering and heading stage. The drought tolerance of rice root at different stages is not the same, the root length, root surface area, root volume can be promoted owing to mild or moderate water stress during water stress of tillering stage, the promoting effects is not significant after re-watering; while water stress at heading stage，the inhibitory action of water stress to root growth is not significant, the root of light, moderate water stress was stronger than that of the control after re-watering.Ten days after re-watering at tillering stage, the qualities of root dry matter and shoot dry matter of control were the highest. Ten days after re-watering at heading stage, the quantities of root dry matter and shoot dry matter with mild and moderate treatment higher than those of the control, and there was a drastic contrast between the qualities of root dry matter and shoot dry matter and those of the control. In maturation stage, the qualities of root dry matter dealt with all kinds of water stress at tillering and heading stag are higher than those of the control. However, it was only with mild treatment at tillering stage that the quality of shoot dry matter and grain yield were higher than that of the control, The quality of shoot dry matter and grain yield with normal water treatment at heading stage was up to its summit. The grain yield with suitable water stress at tillering and heading stage do not significant reduce the yield of rice. Severe water stress does not inhibit root growth, but it decreases the yield of rice significantly.

Increasing drought and extreme rainfall are major threats to maize production in the United States. However, compared to drought impact, the impact of excessive rainfall on crop yield remains unresolved. Here, we present observational evidence from crop yield and insurance data that excessive rainfall can reduce maize yield up to -34% (-17 ± 3% on average) in the United States relative to the expected yield from the long-term trend, comparable to the up to -37% loss by extreme drought (-32 ± 2% on average) from 1981 to 2016. Drought consistently decreases maize yield due to water deficiency and concurrent heat, with greater yield loss for rainfed maize in wetter areas. Excessive rainfall can have either negative or positive impact on crop yield, and its sign varies regionally. Excessive rainfall decreases maize yield significantly in cooler areas in conjunction with poorly drained soils, and such yield loss gets exacerbated under the condition of high preseason soil water storage. Current process-based crop models cannot capture the yield loss from excessive rainfall and overestimate yield under wet conditions. Our results highlight the need for improved understanding and modeling of the excessive rainfall impact on crop yield.© 2019 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

极端降水在全球范围内呈现广泛增强的趋势,对农业生态系统的影响不容忽视。水稻作为重要的粮食作物,其产量的年际波动受到极端降水的影响,然而其响应机理和时空敏感性尚未厘清。论文总结了极端降水在水稻主产区的时空格局及对产量的影响程度,梳理了极端降水对水稻产量的生理、化学和物理过程的影响机制,对比分析了多个主流方法(统计模型和作物过程模型)的输入数据和应用上的优缺点。结果表明,极端降水增加1%导致水稻减产0.02%~0.5%,主要通过增加养分流失和造成淹水胁迫等途径。然而当前研究仍难以明确水稻产量如何响应于极端降水的不同特征值(强度、频次、持续时间等)及其敏感性的时空差异,尚未完善极端降水对水稻各产量组成的影响机理,同时缺乏作物模型与统计模型等相结合的研究方法,造成水稻产量预测的不确定性。建议未来相关研究应加强田间观测、控制性实验与模型改进,定量解析极端降水对产量的影响机理,促进模型—数据融合,提高数据精度以更好地模拟极端降水事件下的水稻产量,为优化当前稻作系统和建立气候智能型农业奠定理论基础。

The increasing trend of extreme precipitation has become stronger globally, and is expected to have detrimental impact on agricultural ecosystems. Rice is one of the staple foods, and the inter-annual fluctuation of rice yield is highly affected by extreme precipitation. However, the mechanisms and spatiotemporal sensitivity of rice yield to extreme precipitation have not been clarified. This review summarized the temporal and spatial patterns of extreme precipitation in the main rice-producing regions of the world and its impact on rice yield, and explored the mechanism of extreme precipitation impact on rice growth and yield from the perspective of physiological, chemical, and physical processes. The input data and advantages and disadvantages in application of the main research methods, including statistical model and crop model, were evaluated and compared. The results indicate that an increase of 1% in extreme precipitation led to a decrease in rice yield by 0.02%-0.5%, mainly through increased nutrient loss and flooding. Yet, large uncertainties still exist in rice yield prediction of current studies, because it is difficult to clarify how rice yield responds to different characteristics (intensity, frequency, and duration) of extreme precipitation and its spatiotemporal sensitivity, and the mechanisms of extreme precipitation affecting rice yield components are not well understood. In addition, lacking the integration of crop models and statistical models also introduces uncertainties. We recommend to promote the integration of multi-methods, especially field observation, controlled experiment, and model improvement, to quantitatively analyze the mechanism of extreme precipitation impact on yield components, and to improve data accuracy to better simulate rice yields under extreme precipitation events in the future. Achieving these progresses will lay a foundation for optimizing the current rice cropping system and agricultural management to mitigate the impact of extreme precipitation.

湖北省是中国重要的植棉省份之一,气候和管理因素变化对棉花生长产生重要影响。因此,本文采用1986—2016年湖北气温、降水量和太阳辐射量3个气候因子数据,有效灌溉面积、农用化肥施用量和棉花品种3个管理因素数据,构建了面板回归模型,定量计算得到气候因子和管理因素的趋势和波动变化对棉花单产的影响及其相对贡献率。结果表明：① 气候和管理因素的波动变化大于气候和管理因素的趋势变化对棉花单产的影响。② 气温和太阳辐射量对湖北省大部分地级市的棉花单产呈现正影响,降水量对湖北省大部分地级市的棉花单产呈现负影响;有效灌溉面积、农用化肥施用量和棉花品种都对湖北省大部分地级市的棉花单产呈现正影响。③ 气温、降水量和有效灌溉面积是影响湖北省大部分地级市棉花单产的主导因子。④ 1986—2016年武汉市等地级市棉花增产的主要原因是管理因素变化主导的增产抵消了气候因子变化的减产影响。