## 3 Results
### Trends in Climatic Factors and Their Mechanisms of Influence on ET
The effect of TMP (Figure 12f) on Et showed a negative contribution in the central and southern regions and a positive contribution in some northern regions. The contribution of the RAD (Figure 12g) to Et is more dispersed, showing a mixed distribution of regional positive and negative contributions. The contribution of VPD (Figure 12h) to Et is negative in most areas of the study area, especially in the southern and central regions, but the positive contribution of VPD to Et in some parts of the central region is very significant (\(>\)3 mm/a). Figure 12i-l show the contribution of different climatic factors to the change in Ei. The contribution of PRE (Figure 12i) to Ei is positive in most regions. The contribution of TMP (Figure 12j) to Ei is positive in the northern region and some central regions, while the southern region shows a negative contribution. The contribution of the RAD (Figure 11k) to Ei is small, with most areas ranging from \(-\)0.5 to 0.5 mm/a. The contribution of VPD (Figure 12l) to Ei is mostly negative in the study area, especially in the southern region. Figure 12m-p shows the contribution of different climatic factors to Es changes. The contribution of PRE (Figure 12m) to Es is positive in most regions, but the overall contribution is small. The contribution of TMP (Figure 12n) to Es showed a positive and negative mixed spatial pattern, mainly concentrated in the northern and central positive contribution areas. The contribution of the RAD (Figure 12o) to Es is small in most regions, ranging from \(-\)0.5 to 0.5 mm/a. The contribution of VPD (Figure 12p) to Es is mostly negative in the study area, especially in the southern region, showing a significant negative contribution. In order to study the ET and its driving mechanism in the Helong region more clearly, we also analyzed the dominant factors of ET, Et, Ei, and Es under four climate impact factors (PRE, TMP, RAD, and VPD) and vegetation change scenarios simulated by the PT-JPL model. The results of the dominant factor analysis of ET showed that TMP was the main factor affecting its change, accounting for 37.2%. The areas dominated by VPD, PRE, and RAD accounted for 21.9%, 30.5%, and 10.4%, respectively (Figure 13a). For Et, the dominant influence factor is VPD, and its dominant influence area accounts for 67.8%. Compared with ET, the dominant influence area of VPD is significantly increased. For Ei, the dominant influence area of TMP and RAD increased to 37.8% and 40.1%, respectively, and only the dominant influence area of PRE remained stable at a low level of 0.3%. For Es, the dominant influence area of TMP continued to increase, while the dominant influence area of RAD and VPD continued to decrease, reaching 11.8% and 33.8%, respectively, and the dominant influence area of PRE remained at a level of 0.3%. From a distribution point of view, the dominant influence area of TMP is distributed in all regions except the northern and northeastern edges; the dominant influence areas of PRE are mainly distributed in the north and west; the dominant influence area of RAD is distributed in the western region; and the dominant influence areas of VPD are scattered throughout the HLS. TMP had significant effects on ET, Et, Ei, and Es, especially in the central and southern regions. PRE mainly played a leading role in the northern and western regions. RAD had a greater impact on the west, while VPD had a relatively scattered impact on the components of ET. The GOF indices of the structural models constructed by ET, Et, Ei, and Es are 0.58, 0.53, 0.57, and 0.43, respectively (Figure 14). Therefore, from a mathematical point of view, the model that we constructed is feasible. The overall explanation rate of driving factors for ET is more than 68.9%, the overall explanation rate for Et is more than 73.4%, the overall explanation rate for Ei is more than 62.5%, and the overall explanation rate for Es is 7.8%, which is at a low level. Please refer to Table 4 for the specific path coefficient values.