Under global climate change, climate warming and changing precipitation patterns would greatly affect plant phenology and photosynthetic capacity and hence affect the gross primary productivity (GPP) of the sensitive alpine meadow. To deeply understand the variations in GPP, it is important to clarify the joint effects of plant phenology and photosynthetic capacity. In this study, 10-year continuous flux and microclimatic data and in situ phenology period observation data were used to explore the roles of growing season length (GSL) and the seasonal maximal capacity of carbon uptake (GPP_max) on annual cumulative gross primary productivity (GPP_ann). The results indicated that the temperature and water conditions, especially water conditions, dominated GSL and GPP_max and hence determined GPP_ann. Both GSL and GPP_max were dominated by annual precipitation, and the soil water content in August also showed a strong influence over them. GSL and GPP_max together could explain 87% of the variation in GPP_ann. Compared with GSL, GPP_max had stronger effects on the interannual variability (IAV) in GPP_ann. This study provides a new perspective on clarifying the proximate causes of IAV in GPP_ann. The IAV in GPP_ann of alpine ecosystems could be determined by these two key underlying processes, the length of the carbon uptake period and amplitude. These results are of critical importance for improving our ability to predict future changes in alpine meadow ecosystems.

在全球气候变化下，气候变暖和降水模式的变化将极大地影响植物物候和光合能力，从而影响敏感高寒草甸的总初级生产力（GPP）。要深入了解 GPP 的变化，重要的是要阐明植物物候和光合能力的共同影响。本研究利用 10 年连续通量和小气候数据以及原地物候期观测数据，探讨生长期（GSL）和季节最大碳吸收能力（GPP _max）对年累计总初级生产力的影响。 （GPP_安）。结果表明，温度和水分条件，尤其是水分条件，决定了 GSL 和 GPP _max，因此决定了 GPP _ann。GSL 和 GPP _max均以年降水量为主，8 月份土壤含水量也表现出强烈的影响。GSL 和 GPP _{max一起可以解释 GPP ann}中 87% 的变化。与 GSL 相比，GPP _{max对 GPP ann}的年际变率（IAV）的影响更大。_{本研究为阐明 GPP ann}中 IAV 的近因提供了新的视角。GPP 中的_IAV高山生态系统的数量可以由这两个关键的潜在过程决定，即碳吸收期的长度和幅度。这些结果对于提高我们预测高寒草甸生态系统未来变化的能力至关重要。