## 4 Discussion
Overall, most previous studies have shown that SIF data provide a new way to evaluate and estimate the impacts of environmental stress on vegetation growth. Integrating structural information from the NDVI and physiological information from GOSIF measurements will enhance our understanding of the alpine vegetation response to frost dynamics on the Third Pole. There are certain limitations and uncertainties in this study. First, meteorological forcing data have a relatively sparse resolution, resulting in the occasional misidentification of frost days. The definition of frost days in most studies uses 0 \({}^{\circ}\)C as the freezing threshold, but this may result in uncertainties when comparing frost occurrences between the Third Pole and other regions [8]. Therefore, future studies still need ground-based observational data to validate the robustness of the calculation of frost days. Another limitation relates to satellite vegetation observations in the region. Additionally, NDVI products in the Third Pole, as measurements of vegetation activities, may also be affected by clouds, snow cover, or land degradation. Despite the superior spatial and temporal resolution of the GOSIF (0.05\({}^{\circ}\)) compared to earlier SIF products and its extensive data record spanning from 2000 to the present, compared to MODIS data, the GOSIF data are still subject to uncertaintiesarising from factors including meteorological reanalysis data, the quality of OCO-2 SIF, biases in the enhanced vegetation index, and imperfect modeling methods [31; 56]. The different spatial representativeness among meteorological forcing data, MODIS NDVI data, MODIS phenology data, and OCO-2 GOSIF data can also lead to uncertainties in the study. Additionally, our study used only correlation analysis to study the relationship between the GOSIF or NDVI and environmental factors such as frost, temperature, precipitation, and radiation in different seasons. The diverse environmental influences on alpine vegetation were accessed in this study. Moreover, different vegetation types exhibited varied responses to frost, attributed to differences in photosynthetic capacity and metabolic capacities, as well as the duration of their required growing periods. Future studies could focus on frost events to analyze frost effects on different vegetation types and multi-source technology integration. By combining with leaf- and canopy-level auxiliary measurements, satellite SIF validation and mechanistic understanding of the relationship between SIF and photosynthesis are important in this study [57]. In other words, ground-observed SIF at local scales and satellite SIF at the regional scales would be valuable for examining the mechanisms in the future [58]. In the context of global climate change in alpine regions expected to be two to three times faster in the 21 st century than in the 20 th century [59], alpine ecosystems remain the areas most affected by future climate change and will continue to require significant attention in the future [60]. In order to mitigate the ecological, climatological, and social consequences of future climate change, we must understand and quantify the vulnerability of alpine ecosystems to climate variability. In fact, understanding vegetation dynamics of Alpine ecosystems can provide insight into future vegetation-climate feedback [61]. It would be beneficial to broader ecological and climatological implications, particularly in relation to the management of alpine ecosystems under climate change [62].