Study on estimating cotton LAI and aboveground fresh biomass using fractional interception of photosynthetically active radiation data | 基于棉花冠层FPAR的LAI和地上鲜生物量估算研究

Chinese. 研究棉花生育期冠层光合有效辐射截获量（FPAR）与其叶面积指数（LAI）和地上鲜生物量的相关关系，建立FPAR对LAI和地上鲜生物量的估算模型，探讨获取LAI和地上鲜生物量的新方法，为动态监测棉花的生长状况提供科学依据。利用线性光量子传感器，测试新陆早19号和新陆早13号2个棉花品种4种配置种植方式下，冠层在6个关键生育期的光合有效辐射数据，获取FPAR，并同步实测棉花冠层LAI和地上鲜生物量，建立FPAR与LAI和地上鲜生物量的相关方程，同时比较LAI和地上鲜生物量的估测值与实测值的差异。2个棉花品种的FPAR随生育进程呈现类似变化规律：在盛蕾期至开花期迅速增加，于花铃期或盛铃期达最大值，随后逐渐下降；棉花FPAR与LAI和地上鲜生物量均达到极显著正相关关系，其中均以幂指数相关关系为最佳（RFPAR－LAI = 0.851 3**， RFPAR－地上鲜生物量 = 0.746 9**， n = 80）；用FPAR分别估算的LAI和地上鲜生物量，与其实测值的相关关系均达到1%极显著正相关（R实测LAI－估算LAI = 0.818 0**, R实测地上鲜生物量－估算地上鲜生物量 = 0.739 6**, n = 80）。棉花FPAR对LAI的估算精度较其对地上鲜生物量的高，表明利用棉花冠层FPAR可以简单、快捷、非破坏性地估测棉花的LAI和地上鲜生物量。

English. This paper analyzed the correlation of the fractional interception of photosythetically active radiation (FPAR) and leaf area index (LAI), aboveground fresh biomass of cotton canopy respectively, and established modelings for estimating LAI and aboveground fresh biomass. Finally, an experimental approach was taken to prove that the FPAR can be actively used to monitor cotton growing status. The photosythetically active radiation data were recorded by utilizing linear quantum sensor at cotton key growth stages in a field experiment including two cultivars of Xinluzao No. 19 and Xinluzao No.13 with four planting patterns, meanwhile LAI and aboveground fresh biomass were tested at the same sites. The function models for FPAR against cotton LAI and aboveground fresh biomass were established respectively. The differential values were compared between tested data and estimated data for LAI and aboveground fresh biomass respectively. There were a similar variation of FPAR on two varieties at different growth stages: with a rapid increase from full squaring stage to blooming stage, their maximum value were both at blossom stage or full boll stage, afterwards it gradually declined; the best modeling correlation between FPAR and LAI, aboveground fresh biomass of cotton canopy, was power function (RFPAR-LAI = 0.851 3_**, RFPAR－aboveground fresh biomass = 0.746 9**, n = 80). The estimated function for LAI, estimated by using FPAR, had higher precision than aboveground fresh biomass. Correlation between tested LAI and estimated LAI, tested aboveground fresh biomass and estimated aboveground fresh biomass respectively were significant (R tested LAI－estimated LAI = 0.818 0**, R tested aboveground fresh biomass－estimated aboveground fresh biomass = 0.739 6_**_, n = 80). The study shows that it is a simple, effective and non-destructive method to estimate the cotton canopy LAI and aboveground fresh biomass by the fractional interception of photosythetically active radiation data.