基于冠层光合特征参数的棉花生长状况高光谱遥感定量监测

The photosynthesis characteristic parameters such as leaf net photosynthesis rate(Pn), transpiration rate(Tr),stomatal conductance(Gs) and intercellular CO2 concentration(Ci)as one of powerful indices on indicating crop growth status.The chlorophyll fluorescence parameters such as initial fluorescence(Fo),PSII photychemical efficiency(Fv/Fm),PSII photochemical quantum yield (PSII),photosynthetic electron transport rate (ETR),photochemical quenching coefficient(qP) and non-photochemical quenching coefficient(NPQ) were recognized as an inherent probe to explore the relationships between photogynthesis and environment. The absorbe photosythetically active radiation(APAR) and fractional interception of absorbed photosynthetically active radiation (FAPAR) play a decisive role on cotton productivity and yield.It has been unique sunlight and heating condition and crop cultivation patterns, creating a high yield and good quality of cotton in Xinjiang.However,in the cotton growing stage,various stress phenomena have occasionally occurred,such as water stress caused by drought.Nitrogen fertilizing application is inappropriate,resulting in nitrogen overused or nitrogen-stressed,cotton becomes of over vegetative growing or premature senescence.The salinization fields, resulting in cotton the salinity stressed. Above all, it restricted the potential yield of Xinjiang's cotton production. researcher persistently explore a rapid, effective and non-destructive method which was used to monitor cotton growth status.Hyperspectral remote sening is the frontier technology in the current and in decades.From cotton single leaf to canopy, comprehensive and systematic research on relationship between hyperspectral remote sensing data and photosynthesis characteristic parameters, amplified hyperspectral foundation and effects of adverse environmental stress factors exerted on cotton photosynthesis physiology on a large scale. Finally, it provides a scientific method for real-time and rapid monitoring cotton growth status on a large area field by using of hyperspectral remote sensing.

光合作用强度参数（Pn、Tr、Gs和Ci等）是反映作物生长状况最有效的指标之一，叶绿素荧光参数（Fo、Fv/Fm、ΦPSII、ETR、qP和NPQ）则被认为是光合作用与环境关系的内在探针，吸收光合有效辐射（APAR）和吸收光合有效辐射截获量（FAPAR），对棉花的光合生产能力和产量起决定性作用；新疆独特的光热条件和作物栽培模式，成就了棉花的高产与优质。然而，在棉花生长季节里，各种逆境胁迫现象时有发生，限制了新疆棉花生产潜力的发挥。人们一直在探索研究对棉花生长状况快速、有效、无损的监测与诊断方法。而高光谱遥感技术是当前和未来几十年内遥感的前沿技术。从棉花叶片到冠层，开展系统的高光谱遥感信息与光合特征参数的关系研究，扩大了高光谱应用基础性研究的范围，使逆境因子对棉花光合生理的胁迫效应，通过高光谱遥感得以宏观拓展，为实施高光谱遥感实时、快速监测新疆大面积棉花生长状况，提供了理论依据。

获取棉花叶片和冠层的光合特征参数需要多个仪器共同来完成，费时耗力测量的样本数有限，而高光谱分辨率遥感技术可以实现对棉花叶片和冠层信息的快速有效的采集与处理；应用光谱分析技术，建立光谱变量与棉花光合作用特征参数（Pn、Tr、Gs和Ci），叶绿素荧光参数（Fo、Fv/Fm、Fm、ETR、qP和NPQ）及光合有效辐射参数（APAR和FAPAR）的相关关系。结果表明：棉花冠层受到水分胁迫，近红外波段光谱的反射率降低，红光波段的反射率升高，因而光谱反射率的变化可以反映棉花的水分状况。随干旱胁迫，棉花叶片的Yield、qp和Fv/Fm逐渐升高，而Fo和Fm逐渐降低，Fv/Fm是指示棉花生长状况的重要荧光参数。经逐步回归分析，棉花反射光谱分别与叶片的净光合速率Pn和冠层吸收光合有效辐射截获量FAPAR的最大正相关发生在反射光谱近红外759nm、758nm波段处，最大负相关分别发生在红光670nm和675nm波段处。反射光谱与叶绿素荧光最大光化学效率Fv/Fm最大负相关发生在反射光谱761nm波段处。一阶微分光谱与Pn，Fv/Fm的最大正相关分别发生在一阶微分光谱693nm 和558nm波段处，它们的最大负相关分别发生在微分光谱560nm和736nm波段处。利用与Pn和FAPAR最大相关的近红外波段和红光波段反射率分别组成归一化植被指数NDVI、比值植被指数RVI分别反演叶片Pn和冠层的FAPAR精度达80%以上。一阶微分光谱特征波段和红边参数能较好的估算光合作用参数、光合有效辐射参数和叶绿素荧光参数。研究结果表明，高光谱遥感技术定量获取棉花叶片光合特征参数、叶绿素荧光参数及冠层光合有效辐射参数三者之间建立相关，可以非破坏性、高效的宏观拓展棉花的光合生理特性，为高光谱遥感实时、快速监测新疆大面积棉花生长状况，提供了科学依据，其研究成果对于新疆精准农业发展具有重要的意义。