陆军胜, 陈绍民, 黄文敏, 胡田田. 采用SEPLS_ELM模型估算夏玉米地上部生物量和叶面积指数[J]. 农业工程学报, 2021, 37(18): 128-135. DOI: 10.11975/j.issn.1002-6819.2021.18.015
    引用本文: 陆军胜, 陈绍民, 黄文敏, 胡田田. 采用SEPLS_ELM模型估算夏玉米地上部生物量和叶面积指数[J]. 农业工程学报, 2021, 37(18): 128-135. DOI: 10.11975/j.issn.1002-6819.2021.18.015
    Lu Junsheng, Chen Shaomin, Huang Wenmin, Hu Tiantian. Estimation of aboveground biomass and leaf area index of summer maize using SEPLS_ELM model[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(18): 128-135. DOI: 10.11975/j.issn.1002-6819.2021.18.015
    Citation: Lu Junsheng, Chen Shaomin, Huang Wenmin, Hu Tiantian. Estimation of aboveground biomass and leaf area index of summer maize using SEPLS_ELM model[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(18): 128-135. DOI: 10.11975/j.issn.1002-6819.2021.18.015

    采用SEPLS_ELM模型估算夏玉米地上部生物量和叶面积指数

    Estimation of aboveground biomass and leaf area index of summer maize using SEPLS_ELM model

    • 摘要: 利用高光谱数据进行作物生长状况监测具有无损和高效的特点,是现代精准农业发展的必要手段。该研究以连续3 a(2018-2020年)不同水氮供应下夏玉米营养生长期采集的212份植物样品(地上部生物量和叶面积指数)和高光谱实测数据为数据源,分别采用偏最小二乘回归(Partial Least Squares Regression,PLS)、极限学习机(Extreme Learning Machine,ELM)、随机森林(Random Forest,RF)和基于PLS叠加策略的叠加极限学习机算法(Stacked Ensemble Extreme Learning Machine based on the PLS,SEPLS_ELM)构建了夏玉米营养生长期地上部生物量和叶面积指数估算模型。结果表明:基于PLS和ELM构建的夏玉米地上部生物量和叶面积指数估算模型的精度均较低,前者验证集R2低于0.85、均方根误差高于550 kg/hm2,后者R2低于0.90、均方根误差高于0.40 cm2/cm2。相比之下,基于RF和SEPLS_ELM构建的夏玉米营养生长期地上部生物量和叶面积指数估算模型均有着较高的估算精度,SEPLS_ELM模型表现尤为突出,其地上部生物量和叶面积指数估算模型验证集的R2分别为0.955和0.969,均方根误差分别为307.3 kg/hm2和0.24 cm2/cm2,表明叠加集成模型能够充分利用高光谱数据并提高作物地上部生物量和叶面积指数估算精度。

       

      Abstract: Abstract: Hyperspectral remote sensing has widely been used to estimate crop physiological, ecological, and biochemical parameters in recent years. However, most previous studies focused mainly on the selection of sensitive bands or the construction of vegetation index (the combination of sensitive bands) for crop parameter inversion. Particularly, the spectral information of some bands can be lost, and then to reduce the prediction ability of the estimation model. The purpose of this study is to estimate the aboveground biomass and leaf area index of summer maize using all spectral information (spectral bands). Therefore, a three-year (2018-2020) field experiment was also conducted under different water and nitrogen management in the Guanzhong Plain of China. Accordingly, 212 plant samples (aboveground biomass and leaf area index) were collected during the vegetative growth period of summer maize. Prior to plant sample collection, the hyperspectral reflectance data of the summer maize canopy was measured using an ASD FieldSpec 3 portable spectroradiometer. Correspondingly, the estimation model was constructed using Partial Least Squares Regression (PLS), Extreme Learning Machine (ELM), Random Forest (RF), and Stacked Ensemble Extreme Learning Machine (SEPLS_ELM, using the PLS stacked ensemble strategy). The results showed that the estimation accuracy (four estimation models) of the leaf area index of summer maize was higher than that of aboveground biomass. The estimation models of PLS and ELM presented a relatively low accuracy for the aboveground biomass and leaf area index of summer maize, where the determination coefficient (R2) for the validation set of the aboveground biomass estimation model was lower than 0.85, and the Root Mean Square Error (RMSE) was higher than 550 kg/hm-2, whereas, the R2 for the validation set of leaf area index estimation model was lower than 0.90, and the RMSE was higher than 0.40 cm2/cm2. The estimation model of aboveground biomass and leaf area index of summer maize using RF and SEPLS_ELM presented a higher estimation accuracy, particularly that the performance of the SEPLS_ELM model was outstanding. The R2 values for the validation set of aboveground biomass and leaf area index estimation model using the SEPLS_ELM model were 0.955 and 0.969, while the RMSE were 307.3 kg/hm2 and 0.24 cm2/cm2, and the Residual Predictive Deviation (RPD) were 4.66 and 5.30, respectively. Compared with PLS and ELM, the estimation accuracy of the SEPLS_ELM model was significantly improved (the R2 increased by more than 8%, RMSE decreased by more than 40%, and RPD increased by more than 70%, respectively) in aboveground biomass and leaf area index estimation. Compared with the RF, the R2 of the SEPLS_ELM estimation model increased by more than 7%, RMSE decreased by more than 40%, and RPD increased by more than 66% in the aboveground biomass and leaf area index estimation of summer maize, respectively. Consequently, the present study demonstrated that the SEPLS_ELM model was highly reliable to predict the aboveground biomass and leaf area index of summer maize. The findings can provide a strong reference for the estimation of crop aboveground biomass and leaf area index using hyperspectral remote sensing.

       

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