The superiority of solar-induced chlorophyll fluorescence sensitivity over other vegetation indices to drought

Solar-induced chlorophyll fluorescence (SIF), which is directly related to photosynthetic activity, has an advantage over greenness-based vegetation indices (VIs) in quantifying the impact of drought on vegetation. However, understanding of differences in the sensitivity of SIF and VIs to drought is still limited to specific vegetation types, especially at multiple temporal scales. In this study, we compared the sensitivity of satellite SIF and traditional VIs, the normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), and near-infrared reflectance of vegetation (NIRv) to droughts based on standardized precipitation-evapotranspiration index (SPEI) of different time scales across different vegetation types in a typical drought year in China. SIF showed a timely response to the drought event with negative change and decreased more significantly than NDVI, EVI, and NIRv for all vegetation types. The relationships between the change of SIF and 3-month SPEI were the best in grasslands and forests (r > 0.6, p < 0.05). SIF in croplands was more affected by soil moisture and closely related to long-term SPEIs (>3 months). Our work provides a comprehensive understanding of SIF sensitivity to drought across different vegetation types and multiple temporal scales.