Non-Destructive Estimation of SPAD and Biomass in Lamiophlomis rotata Using Hyperspectral Imaging and Deep Learning with DRSA-CARS Feature Selection

Xuemei Wu¹Liwen Zhong²Rong Ding¹Chenghui Wang¹Hongchuan Chen²Shihong Zhong³Rui Gu^1*

• ¹School of Ethnic Medicine, Chengdu University of Traditional Chinese Medicine, Chengdu, China
• ²Chengdu University of Traditional Chinese Medicine School of Pharmacy, Chengdu, China
• ³Southwest Minzu University, Chengdu, China

Monitoring the growth status and above-ground biomass of wild and cultivated medicinal herbs remains a persistent challenge in precision agriculture. In this study, we developed machine learning and deep learning models to estimate SPAD values and biomass of Lamiophlomis rotata (Benth.). Models used hyperspectral data and time-series phenotypic traits from 508 samples collected across different altitudes. Regions of interest (ROIs) were manually defined from plant contours. The corresponding mean spectral profiles were then preprocessed. To improve feature selection, we proposed a Dynamic Reptile Search Algorithm-enhanced CARS (DRSA-CARS) method. This method integrates a dynamic behavioral strategy into the CARS framework to identify informative spectral bands. Vegetation indices (VIs) and gray level co-occurrence matrix (GLCM) based texture parameters were extracted and combined with spectral features to construct PLSR, SVR, FNN, and CNN models. Compared to CARS, the DRSA-CARS method reduced feature dimensionality by up to 75.7% for SPAD and 29.2% for biomass, while improving prediction accuracy (R²) by 24.4% and 34.7%, respectively. Among all models, the FNN achieved the highest performance, with R² values of 0.7732 (training) and 0.7502 (testing) for SPAD, and 0.8260 and 0.7933 for biomass. Feature fusion further improved predictive accuracy by 11% for SPAD and 30% for biomass compared to models based on individual feature types. These results demonstrate that coupling DRSA-CARS-based feature selection with deep learning provides a robust, non-destructive approach for evaluating plant growth status. This framework highlights the potential of hyperspectral imaging as a rapid, reliable, non-invasive tool for precision cultivation of medicinal herbs.