## 3 Results
### Correlation between ANPP and Climate Factors and Heterogeneity Distribution on Elevation Gradient  
According to Figure 9, from 2001 to 2018 in the study area, both the annual average temperature and total precipitation exhibited an upward trend. Figure 10 shows the distribution of the annual average temperature and total precipitation in the study area. The inter-annual variation in the annual average temperature was substantial, while the increase in total precipitation was relatively stable. The annual average temperature increased at a rate of 0.02 \({}^{\circ}\)C yr\({}^{-1}\), and the speed of precipitation increase was 14.90 mm yr\({}^{-1}\). Figure 8: Effects of human activities and climate change on ANPP under eight scenarios. Figure 9: Trends in precipitation and annual mean temperature from 2001 to 2018. A partial correlation analysis was utilized to examine the relationship between climatic factors (annual total precipitation and annual average temperature) from 2001 to 2018 and ANPP in the study area. Figure 11 indicates the partial correlation coefficient between ANPP and temperature, where areas with a significant positive correlation were primarily located on both sides of the Daba Mountains spanning across Shaanxi and Sichuan provinces, both flanks of the Daliang Mountains and Wulian Peaks, and other mentioned regions. This suggests that in these areas, a rise in temperature facilitated the growth of ANPP, whereas it impeded it otherwise. Regions with a significantly negative correlation were more concentrated in specific zones mentioned, indicating that in these parts, a temperature increase was detrimental to ANPP growth, and a decrease was favorable instead. Figure 11 represents the partial correlation coefficient between ANPP and precipitation. Interestingly, areas within the study region where the ANPP was significantly correlated with precipitation exhibited pronounced spatial differences. The areas with positive correlations primarily occupied the central, western, and northern parts of the study region, while negative correlations were concentrated in the southeastern coastal sections. Significant positive correlation areas predominantly occurred in specific mentioned mountainous and provincial regions, indicating that an increase in precipitation was beneficial to the enhancement of the ANPP in these locations, whereas it led to a  
Figure 11: Partial correlation coefficient between ANPP and (**a**) precipitation and (**b**) annual mean temperature. Figure 10: Spatial distribution of (**a**) precipitation and (**b**) mean annual temperature from 2001 to 2018.  
decrease in the ANPP otherwise. Conversely, areas with a significantly negative correlation were mainly located in particular ecological protection zones and other mentioned areas, implying that increased precipitation in these regions was not conducive to ANPP growth, but a reduction in precipitation facilitates it. The annual average temperature and total precipitation also exhibited different heterogeneous distributions at various altitudinal gradients. With the increase in altitude, both the annual average temperature and the total precipitation were in an overall declining trend (Figure 12). Regarding the correlation between ANPP and annual average temperature or total precipitation, if more than 50% of the pixels within a specific altitude range exhibited a positive (negative) correlation between ANPP and temperature (precipitation), it was determined that ANPP has a positive (negative) correlation with temperature (precipitation) in that range. Within 50 elevation bins ranging from 0 to 5000 m (at 100 m intervals), 82% of the bins showed a positive correlation between the ANPP and the annual average temperature, while 18% displayed a negative correlation, only occurring within the 1900 m to 2800 m elevation range.