## 4 Discussion
### Response of NPP to Meteorological Factors in Different Grasslands Cover Types  
Grasslands with different cover types displayed different variation characteristics. High-coverage grasslands had a low increase rate, but low-coverage grasslands had a high increase rate. The NPP variation of medium-coverage grasslands and their responses to climate factors fall between high-coverage and low-coverage grasslands. Meteorological factors play a crucial role in shaping these trends (Figure 8b). Our research provides insights into how climate change interacts with all three types of grasslands of the TP.  
Precipitation is the most significant factor affecting NPP in low-coverage grasslands, and radiation has no effect, while temperature has a negative effect (Figure 9). This is due to the geographic distribution of low-coverage grasslands in the TP. On the one hand, precipitation increases in low-coverage grasslands, mitigating the impact of soil water deficits. It has been demonstrated that wetter and warmer climatic conditions will alleviate low-temperature constraints and promote the growth of alpine vegetation [70; 71]. In regions with lower precipitation, NPP shows a rapid increase with precipitation until it reaches a threshold [72]. On the other hand, low-coverage grassland is predominantly situated in the permafrost region of the west-central plateau, and more permafrost water is released into the soil under the impact of global warming. However, higher temperatures may enhance soil evapotranspiration, exacerbating soil moisture deficits at higher elevations and leading to a declining trend in the effect of temperature on NPP. Previous studies have indicated that climate warming may impede vegetation growth on the TP by increasing soil moisture deficits, which is consistent with the findings of this study [73; 74]. Precipitation is the dominant factor of NPP change in high-coverage grassland, followed by radiation and temperature factors. However, the NPP change of high-coverage grassland in the eastern and southern regions of the TP is influenced most by temperature and radiation. That is because seasonally frozen soil maintains relatively high soil moisture content during the growing season and it promotes the impact of radiation and temperature.  
At the same time, it is important to consider the influence of non-meteorological factors. China has implemented ecological restoration projects, which have helped reduce grassland degradation caused by grazing. [PERSON] et al. [75] found that grazing intensity (14.5%) had a lower impact on controlling Above-ground Net Primary Production (ANPP) grassland dynamics compared to precipitation (29.0%). However, precipitation variability was identified as the key factor for increasing alpine grassland ANPP across the plateau. Meanwhile, under different precipitation patterns, summer precipitation can provide a  
Figure 10: Temporal trends of meteorological factors (precipitation, radiation, temperature) from 1979 to 2018, the dashed lines represents a linear trend.  
more effective water supply to the vegetation than meltwater from snowfall or glaciers [69]. The NPP of grasslands on the Tibetan Plateau is expected to increase due to the combined effects of meteorological and non-meteorological factors. In terms of stability, precipitation and temperature variability have a greater impact on the stability of alpine meadows, while temperature variability does not significantly affect grassland stability [76]. It is predicted that the vulnerability of alpine meadows to climate change in the west-central Tibetan Plateau will decrease in the future [77].