Study on the spatiotemporal variations of vegetation phenology in China based on solar-induced chlorophyll fluorescence.

This study analyzed the temporal and spatial dynamics of vegetation phenology using high-resolution solar-induced chlorophyll fluorescence (HCSIF) data combined with meteorological and land use data. Regression, stability, continuity, and correlation analyses were conducted to evaluate the effects of climate change on vegetation phenology in China over the past 20 years. The results showed that, first, the start of the season (SOS) ranged from early January to mid-May and the end of the season (EOS) from mid-August to late December, with an average growing season (LOS) of 8 months. Over 20 years, SOS advanced by 0.02 days/year, EOS was delayed by 0.23 days/year, and LOS lengthened by 0.13 days/year. Second, most vegetation types exhibited delayed EOS and prolonged LOS, except grasslands and shrubs, which showed slightly advanced EOS and shortened LOS. Cultivated land and natural vegetation experienced the most significant changes, with SOS advancing by 0.66 days/year, EOS delaying by 0.97 days/year, and LOS increasing by 1.37 days/year. Lastly, elevation and urbanization had notable effects: every 500-m elevation increase advanced SOS by 3.67 days, delayed EOS by 2.87 days, and extended LOS by 6.53 days; a 10% urbanization increase led to a 1.37 days/year SOS advance, 2.22 days/year EOS delay, and 3.09 days/year LOS extension. Meteorological factors strongly influenced the phenological changes, particularly in cultivated and natural vegetation.