High-Accuracy Remote Sensing Identification of Winter Wheat Based on Feature Selection and Cross-Temporal Fusion in Shandong Province, China

Accurate crop distribution mapping using multi-temporal remote sensing has become increasingly important for agricultural monitoring and management. However, existing methods often rely on the direct stacking of multi-temporal features, which leads to feature redundancy and reduced model efficiency. To address this issue, this study proposes a winter wheat identification framework that integrates growth-stage ranking, key spectral variable selection, and cross-temporal feature fusion. Taking Shandong Province as the study area, eight typical growth stages during the 2023–2024 winter wheat growing season were analyzed using Sentinel-2 imagery. Random Forest models were first constructed for each growth stage to evaluate discriminative ability. Then, spectral variable contributions were quantified using permutation importance, and key spectral variables were selected under correlation constraints. The progressive accumulation model (PAM) was then developed according to the ranking of discriminative ability across different growth stages, while the cross-temporal fusion model (CTFM) was constructed by extracting inter-stage mean values (mean) and inter-stage differences (diff) of key variables. The results show that the feature space was reduced from 64 dimensions (8 stages × 8 variables) to 16 key variables, substantially improving feature representation efficiency. Among the eight growth stages, the jointing, overwintering, heading, and grain-filling stages exhibited relatively strong discriminative ability. In the cross-temporal experiments, CTFM M6, which integrates information from the top six growth stages ranked by discriminative ability, achieved an overall accuracy (OA) of 0.9658 and a user’s accuracy (UA) of 0.9609 using only 10 fused features, providing the best balance between identification accuracy and feature dimensionality. Based on this model, a 10 m resolution winter wheat distribution map of Shandong Province was generated, and the estimated planting area showed high consistency with statistical yearbook data. These results demonstrate that the proposed strategy can effectively reduce feature dimensionality while maintaining high identification accuracy, providing an efficient and scalable approach for regional-scale remote sensing mapping of winter wheat.