Effect of waterlogging on carbon isotope discrimination during photosynthesis in Larix gmelinii

Soil moisture is a major factor controlling carbon isotope discrimination (Δ¹³C), which has been demonstrated to decrease under dry conditions in many studies; however, few studies on Δ¹³C under waterlogging condition have been conducted. In this study, a pot experiment was conducted with Larix gmelinii, a major larch species in the east Siberian Taiga, to investigate the effect of waterlogging on Δ¹³C during photosynthesis. Assimilation rate and Δ¹³C_RD (instantaneous Δ¹³C calculated with Rayleigh distillation equation) decreased drastically soon after waterlogging, followed by recovery in their values, which was caused by a change in stomatal conductance. Thereafter, assimilation rate decreased gradually, whereas Δ¹³C_RD decreased more gently. These results were thought to be caused by the decrease in both stomatal conductance and carboxylation. Our results indicate that extreme wet events may cause a decrease in Δ¹³C, which is important information for detecting flooding events in the past using tree-ring isotope analyses and for studying impacts of flooding on plants in areas where waterlogging might occur.     

洪涝胁迫的水稻叶面积指数变化及其光谱响应研究

通过水稻淹水实验模拟洪涝胁迫状态,分析不同生育期、不同洪涝胁迫强度下的水稻叶面积指数变化及其冠层高光谱响应规律,建立洪涝胁迫下水稻叶面积指数(LAI)的估测模型。结果表明,分蘖期、拔节期、抽穗期水稻LAI均随淹水深度的增加而降低;水稻冠层680~760 nm光谱的一阶微分具有“双峰”现象,主峰位于724~737 nm,701和718 nm有次峰出现,并随淹水深度的增加出现“三峰”;冠层红边位置在各个生育期出现“蓝移”,红边幅值、红边面积在分蘖期、拔节期、灌浆期均呈现“蓝移”,在抽穗期出现“红移”;生育前期水稻LAI与光谱特征参量存在显著相关,生育后期相关性不显著;最后以D_λ737/D_λ718光谱参量建立了水稻生育前期的LAI估测模型。表明在洪涝胁迫下,水稻LAI的变化幅度直接反映胁迫强度的大小,估测模型LAI=3.138(D_λ737/D_λ718)-0.806可用于估测洪涝胁迫不同强度下的水稻叶面积指数。     

小麦渍害光谱特征分析

理清小麦渍害光谱特征是大尺度渍害遥感监测的基础,也是运用光谱特征实现无损、快捷鉴别小麦渍害的前期条件,迄今为止未见对小麦渍害光谱特征的相关研究。该研究通过田间实验分析了8个小麦品种(郑麦9023、西农223、漯6010、富麦168、鄂麦23、鄂麦19、广源11-2、农大195)受渍后叶片和冠层的光谱特征与没有渍害小麦光谱特征的差异,研究表明：受渍后叶片光谱反射率较正常叶片的差异主要表现在645～680 nm区间(红光波段),较正常值偏高;757～917 nm区间(近红外波段),较正常值偏低;1 428～1 456 nm区间,较正常值高;1 641～1 684 nm区间,较正常值低,主要原因：一是渍害导致叶片叶绿素光合作用能力下降,二是叶片失水引起水势降低,建议用归一化水指数(NDWI)的差异值反映小麦受渍情况,同时分析了不同小麦品种受渍时与受渍后NDWI指数随时间的变化特点,发现其变化特征与小麦品种的抗性有关;受渍后小麦冠层的所有波段光谱反射率均低于正常小麦,建议用670～2 400 nm光谱反射率的均值差异反映小麦受渍情况。     

城市内涝监测预警信息系统研究

针对越来越严重的暴雨至涝现象,为了让普通民众可以通过智能移动终端应用便捷地获取并分享汛情信息,更好地避灾避险并参与到抢险救灾中,基于现有城市道路积水监测系统的基础数据,采用移动GIS和云服务等技术,设计了具有道路实时积水呈现、道路通行重要告警、汛情实景图片、政府信息通告等功能的一体化城市内涝监测预警信息系统。该系统包括内涝监测预警信息服务平台和智能移动终端应用两部分,基于云技术构建“内涝监测e警”平台并设计了基于移动云服务的数据统一调度与管理,基于移动Web技术开发“内涝监测e警”智能终端应用,应用和平台之间基于移动Web和移动GIS技术实现数据访问。测试显示该系统支持大量用户的并发访问,能够简洁有效实现内涝监测数据信息共享,对城市内涝监测预警具有实际的应用意义。