Abstract: Climate change has significantly altered the carbon and water cycles of terrestrial ecosystems. Climate change and the extended vegetation growing season enhanced ecosystem gross primary production (GPP). However, the relative contributions of climate drivers and vegetation phenology to GPP remain unclear. Based on satellite-derived vegetation phenology and GPP datasets from 1982 to 2018, we investigated the spatiotemporal patterns of GPP and its drivers in the Jinsha River watershed. We found that the growing season GPP significantly increased from 1982 to 2018, which was primarily attributed to changes in the growing season length (GSL) and temperature. The effect of GSL on GPP was the highest (r = 0.34), with its effect being larger than that of temperature, precipitation and radiation in 41% of the watershed. Importantly, the area where GPP was predominantly influenced by GSL increased by 12% in grid cells during the period of 2001–2018 compared with 1982–2000, indicating that GSL was playing an increasingly important role in driving GPP. Our findings highlight the dynamic responses of GPP to climate change and the associated phenological variations, which are crucial for improving the understanding of the terrestrial carbon balance.

Key words: climate change, growing season length, gross primary production, dynamic drivers, Jinsha River watershed