## 3 Results
### Spatiotemporal Pattern of Carbon Fluxes
#### 3.1.3 Trend Distribution of Carbon Fluxes  
The carbon fluxes of the alpine grasslands in the study area were significantly increased using the Sen-MK approach. The GPP of TRSR alpine grassland demonstrated an overall rising trend over the 34-year time range (Figure 7). The locations with significant GPP increases accounted for the majority (90.12%); the regions with significant GPP decreases accounted for only 4.79%, indicating a remarkable upward trend in grassland ecosystem productivity. The regions with significant increases, increases, significant decreases, and decreases in NEP accounted for 48.60%, 43.98%, 0.21%, and 7.22% of the total area, respectively. The significantly increased pixels were mainly apparent in the YRSP's western and southern regions, as well as in the majority of the HRSP. There were only a few isolated and dispersed areas with significant NEP declines, such as Dali County, east of the TRSR. There were contrasts in the improvement effect of carbon fluxes in various time frames. From 1985 to 2000 (Figure 8a), the regions that increased significantly, accounting for 22.84% of GPP, were mostly concentrated in the western YRSP and the areas around the HRSP. However, between 2001 and 2018, approximately 68.53% of the grassland exhibited a significantly increasing tendency. Only 1.38% of the district saw a decrease, which was, for the most part, dispersed in the eastern part of the YRSP. Thus, grassland GPP increased significantly between 2001 and 2018 compared to the 1985-2000 period. A comparison of NEP in these two time periods revealed that the proportion of substantial increases in NEP in 2000-2018 (5.77%) was greater than that in 1985-2000 (2.11%). Additionally, the region with a considerable NEP decline after 2000 (0.21%) was reduced compared to that in the previous decade (1.49%). According to the geographical distribution, the dramatic decline in NEP from 1985 to 2000 was localized in the TRSR's northeastern region. The western YRSP saw a significant increase from 2001 to 2018. As a whole, NEP after 2000 was slightly greater than before. Figure 6: Area proportion of the different carbon flux distribution intervals. Carbon flux patterns across the three sub-park sections were investigated at different intervals of time (Figure 8). The grassland GPP increased dramatically across all three sub-park regions throughout the 34-year time range. The area with the greatest increase in GPP was the HRSP (96.12%). Meanwhile, the YRSP (94.97%) and LRSP (84.15%) regions with increased GPP were roughly comparable. Across the three sub-park regions, the percentages of locations with GPP reductions were all low. Prior to the 21 st century, the three sub-park areas had a low percentage of regions that experienced significant increases in GPP. The percentages of significant increases in GPP in the YRSP, HRSP, and LRSP were  
Figure 8: Area percentages of changes in GPP (**a**) and NEP (**b**) in different regions. Figure 7: The spatial distribution of the trend of alpine grassland GPP (**a**,**c**,**e**) and NEP (**b**,**d**,**f**) in the TRSR during the different periods. 36.74%, 31.65%, and 5.28%, respectively. In contrast, there was a considerable spike in the number of regions with a significant increase in GPP after the 21 st century for the three source regions. The area with the greatest increase in GPP also had the greatest share of the YRSP (84.34%). The proportions were identical in the HRSP (75.14%) and LRSP (49.16%) source areas, and practically no location showed a significant decrease in GPP. The NEP of the sub-park regions followed the same pattern as the GPP. In all three sub-park areas, the Prairie NEP expanded over the 34-year period. The proportion of regions with significantly increased NEP in both the YRSP and the HRSP was greater than 70%. Only 16.21% of the LRSP area had a significant increase in NEP, which was noteworthy to administrators.