## 4 Discussion
### Possible Reasons for T\({}_{\text{min}}\) in Determining Plant Growth over the TP
One potential explanation is that an elevation in \(T_{\text{min}}\) may lead to a decrease in the volume of endosperm cells during the vegetation's mature stage [53], and the accelerated rate of vegetation autotrophic respiration [54] may lead to a shortened grain-filling period for the vegetation [55]. In addition, this study reveals a stronger correlation between air temperature and vegetation growth in seasonal frozen grounds and permafrost regions compared to unfrozen grounds (Figure 7 and Table 1). This is in good agreement with [PERSON] et al. [56], who reported that temperature at high altitude (>3500 m) has a stronger influence on NDVI than at lower altitudes. The results of the GeoDetector further confirmed that the explanation of air temperature on vegetation growth is highest in seasonal frozen regions, followed by permafrost. One possible explanation for this may be related to the fact that in seasonal frozen soil regions and in permafrost regions, the increasing rates of \(T_{\text{min}}\) and \(T_{\text{max}}\) are higher than in unfrozen regions (Figure 5). Additionally, the unfrozen region of the vegetation area typically receives sufficient precipitation and light. In contrast, the seasonal frozen grounds and permafrost regions are located at relatively higher altitudes, which experience colder and drier climates, and which undergo surface soil freeze-thaw cycles [57; 58; 59]. The rise in air temperature has led to an earlier timing of seasonal thaw during the past decades, and the relative increase in plant-available moisture will further promote vegetation growth [60]. Finally, an interesting finding of this study is the asymmetric influence of \(T_{\text{min}}\) and \(T_{\text{max}}\) on vegetation growth. Specifically, the results show that \(T_{\text{min}}\) is the dominant factor influencing plant growth in the western TP, while vegetation in the eastern area is predominantly affected by \(T_{\text{max}}\). The restricted soil freeze-thaw conditions in the western alpine region make it mainly controlled by \(T_{\text{min}}\), as reported by [PERSON] et al. [44] By contrast, \(T_{\text{max}}\) is significantly negatively correlated with NDVI and GPP in part of the western TP (Figure 6b). This result may be explained by the fact that in regions with less precipitation, daytime warming can cause higher evapotranspiration and lower soil water content, and higher T\({}_{\rm max}\) can exacerbate the effects of drought. Therefore, the arid climate, especially the water deficit due to the high T\({}_{\rm max}\), will lead to a weak correlation between T\({}_{\rm max}\) and plant growth [57], and it will even restrict the growth of vegetation. Additionally, a decrease in NDVI can lower latent heat and increase sensible heat, leading to further warming [61]. With increasing temperatures, significant changes in soil moisture within the root zone adversely impact vegetation photosynthesis in relatively arid regions [62]. [PERSON] et al. [63] have also proposed that an increase in daytime temperature is beneficial for plant growth and its ecosystem carbon sequestration function in most humid regions, but that it is not favorable for plant growth in arid regions. Moreover, ecological processes are also considered as critical factors influencing the differential effects of T\({}_{\rm min}\) and T\({}_{\rm max}\) on plant growth. The increases in T\({}_{\rm max}\) and T\({}_{\rm min}\) affect different plant species, and each displays unique adaptability. For plant species in different frozen soil regions, there are variations in the timing of leaf unfolding and senescence adjustments to adapt to seasonal changes [64], and this adaptation allows them to optimize carbon uptake and minimize water loss, thereby ensuring their survival and resilience in response to changing environmental conditions [65].