Quantifying the impact of dust retention on maize canopy spectral reflectance and vegetation indices in dust belt regions: A case study in southern Xinjiang, China

Sand dust belts span approximately one-fifth of the global land surface. In these regions, dust tends to settle on vegetation surfaces, altering the observed reflectance and affecting remote sensing detections. To enhance the accuracy of maize growth monitoring in dust-affected regions, this study aims to quantify the effect of sand dust retention on maize during the tasseling stage in the Kashgar Prefecture, Xinjiang Uygur Autonomous Region, China, by analyzing changes in canopy reflectance and vegetation indices. First, field sampling was conducted to measure the key canopy structure parameters and dust retention levels of maize, and laboratory spectral measurements were performed on leaf spectral properties under gradient dust retention. The measured data were then used to drive the LargE-Scale remote sensing data and image Simulation framework (LESS) model for simulating realistic maize canopy spectra across different dust levels, with validation against Sentinel-2 imagery. Second, on the basis of the simulated and satellite-derived spectra, the dust resistance of 36 common vegetation indices was systematically evaluated, and new robust dust-resistant indices were developed. The results showed that compared with dust-free maize, the canopy reflectance of dust-retained maize followed an increase–decrease–increase pattern, with critical turning points at 735 and 1325 nm. The maximum reflectance difference of –0.11755 (change rate: 29.002%) occurred within the 735–1325 nm range at 24 g/m 2 dust retention, and the minimum reflectance difference of 0.04285 (change rate: 148.950%) was observed in the 350–735 nm range under the same dust retention level. Among the 36 vegetation indices, only the global environment monitoring index (GEMI) and the ratio of transformed chlorophyll absorption in reflectance index to optimized soil-adjusted vegetation index (TCARI/OSAVI) exhibited dust resistance, with GEMI being effective below 6 g/m 2 and TCARI/OSAVI remaining stable across all levels (average ratio: 0.970). The newly developed indices in this study, (RE3–RE2)/(NIR–RE2), (RE3–RE2)/(RE4–RE2), and (NIR–RE2)/(RE4–RE2), retained values within the predefined dust-resistant range over the full dust retention levels of 0–24 g/m 2 , thus showing a more stable dust resistance compared with the commonly used 36 vegetation indices. Specially, (RE3–RE2)/(RE4–RE2) performed the most robustly in Sentinel-2 imagery, that is, 58.020% of pixels were within the dust-resistant range, and an average ratio of 0.937 was obtained for the original-spectra index. This study provides a scientific basis for crop monitoring and management in dust-affected regions.