Optical remote sensing for capturing recent vegetation phenology changes

Accurately tracking vegetation phenology is crucial for understanding ecosystem responses to climate change, yet different remote sensing methods yield varying estimates. Traditional indices like MODIS NDVI often overestimate the duration of active photosynthesis compared to solar-induced chlorophyll fluorescence (SIF), which more directly measures photosynthetic activity. In grasslands, precipitation is increasingly shaping late-season phenology, a trend projected to intensify. Despite climate-driven shifts in growing season length, the green-up to senescence ratio has remained stable in northern ecosystems, suggesting intrinsic biotic regulation. These findings underscore the need for multi-sensor approaches to refine phenological assessments and improve Earth system modeling.