Abstract: The alpine canyon regions of Southwest China serve as a vital ecological security barrier for the country. Photosynthesis plays a crucial role in maintaining ecosystem equilibrium. Understanding the characteristics of vegetation photosynthetic dynamics and their driving mechanisms holds significant practical value for assessing ecosystem health and addressing climate change challenges. We utilized GOSIF data to analyze spatiotemporal variations of vegetation photosynthesis through Sen+MK trend analysis, coefficient of variation, and Hurst index. We further employed geographical detector techniques to investigate the mechanisms underlying spatial differentiation. The results showed that: (1) From 2001 to 2020, the solarinduced chlorophyll fluorescence (SIF) in the alpine canyon area of Southwest China showed a slow and fluctuating upward trend, with a spatial pattern of “high in the south and low in the north”. As the altitude decreased, the SIF showed an increasing trend. (2) The spatial distribution of the overall trend of SIF showed significant heterogeneity, with an increasing proportion of 64.82%, mainly distributed in the northern part of Yunnan Province, as well as Liangshan Yi Autonomous Prefecture and Garze Tibetan Autonomous Prefecture in Sichuan Province. (3) The SIF exhibited good overall stability, while regions distributed at altitudes above 4500 meters showed relatively low stability. The Hurst index was slightly lower than 0.5, indicating that the variation trend of SIF would be generally stable with small fluctuations in the future, and the spatial distribution of its future variation trend is basically consistent with the current spatial pattern of SIF variation trend. (4) The dominant factors driving the spatial differentiation of photosynthetic dynamics were elevation, temperature, evapotranspiration, and precipitation. Compared to single-factor analysis results, the interaction effects revealed that extreme climatic factors exhibited higher levels of influence. These findings provided references for ecosystem conservation and climate change research in the alpine canyon regions of Southwest China.

Key words: vegetation photosynthetic dynamics, solar-induced chlorophyll fluorescence (SIF), driving mechanism, remote sensing, alpine canyon area of Southwest China