基于ACRM模型不同时期冬小麦 LAI和叶绿素反演研究

INVERSION OF LAI AND CHLOROPHYLL CONTENT OF WINTER WHEAT AT DIFFERENT STAGES USING TWO-LAYER CANOPY REFLECTANCE MODEL

关键词:  叶面积指数　叶绿素含量　冠层辐射传输模型　反演

Key words:  LAI  chlorophyll content  winter wheat  ACRM  inversion  HJ-1

摘要:

通过冬小麦4个生育期不同长势冠层光谱观测数据，模拟HJ小卫星多 光谱等效反射率；然后使用双层冠层反射率模型（ACRM）反演各生育期冬小麦LAI和叶绿素含量，分析HJ 小卫星多光谱数据定量反演LAI和叶绿素含量的应用潜力以及ACRM模型在不同冬小麦生育期的LAI和叶绿素 含量反演误差。将模型反演值与实测值对比分析发现：（1）LAI和叶绿素含量反演值与地面实测值有很高 的相关性，应用HJ小卫星多光谱数据定量反演LAI和叶绿素有很大的应用潜力；（2）ACRM模型在不同生育 期的冬小麦LAI和叶绿素含量反演误差存在差异。

Abstract:

LAI and chlorophyll content of crop are key variables for crop growth remote sensing monitoring and yield prediction. Understanding the inversion errors of canopy reflectance model at different stages is quite helpful for choosing an optimal model to estimate LAI and chlorophyll content. The authors investigated the inversion errors of winter wheat LAI and chlorophyll content at different growth stages using a two-layer canopy reflectance model （ACRM） with in situ data. The authors simulated equivalent multi-spectral reflectance of winter wheat canopy with hyper-spectral reflectance， and then set the equivalent multi-spectral reflectance as the inputs of ACRM to retrieve LAI and chlorophyll content. Compared the retrievals of LAI with measurements， the correlation coefficient is 0.836 1， 0.903 0， 0.850 6 and 0.906 3 at each stage， and the maximum error is 0.629 1， 0.426 8， 0.424 4 and 0.276 5， from jointing stage to milk stage; the correlation coefficient of chlorophyll content and SPAD is 0.593 7， 0.897 7， 0.909 2 and 0.936 8 at each stage. The results showed that there is a good capacity for retrieving the LAI and chlorophyll content of winter wheat from jointing stage to milk stage using ACRM， but the errors of inversion are different at each phonological stage， the errors in jointing stage were larger than that in booting stage， heading stage and milk stage. We should consider the accuracy at different stages while using this model to retrieve LAI and chlorophyll content.