## 3 Results
### Interannual Variations in Carbon Fluxes  
By simulating the forest carbon fluxes in Yunnan Province from 2020 to 2060, we observe that the annual means of GPP were 2388.76, 2348.97, and 2344.50 gCm\({}^{-2}\cdot\)yr\({}^{-1}\) in the SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios, respectively (Figure 4). The comparison shows that the SSP1-2.6 scenario had the highest annual mean GPP and the smallest IQR (interquartile range), while the other two scenarios had greater variability in GPP (Figure 5). The three different scenarios show a significant upward trend in GPP, with increased rates of 14.98, 15.46, and 16.30 gCm\({}^{-2}\cdot\)yr\({}^{-1}\), respectively, indicating that GPP increased the fastest in the SSP5-8.5 scenario. Meanwhile, the 5-year moving average of GPP showed that the SSP1-2.6 scenario had a higher GPP than the other scenarios until 2040 and after 2050. Between 2030 and 2040, the GPP for SSP5-8.5 was clearly decreasing.  
The annual means of the ER values were 2254.82, 2227.71, and 2228.59 gCm\({}^{-2}\cdot\)yr\({}^{-1}\) in the SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios, respectively, with increasing trends of 17.28, 17.67, and 18.25 gCm\({}^{-2}\cdot\)yr\({}^{-1}\), respectively. The results of the comparison showed that the SSP2-4.5 scenario had the smallest annual average ER and the lowest rate of change.  
The simulation of NPP found that the highest annual average value of NPP for the next 40 years was 844.84 gCm\({}^{-2}\cdot\)yr\({}^{-1}\) in the SSP1-2.6 scenario, which was significantly higher than that in SSP2-4.5 (817.94 gCm\({}^{-2}\cdot\)yr\({}^{-1}\)) and SSPS-8.5 (818.38 gCm\({}^{-2}\cdot\)yr\({}^{-1}\)). The 5-year sliding average showed that the NPP growth trend continued until the 2050s and peaked in 2052, after which it began to trend downward, and the NPP under the SSP1-2.6 scenario after the 2030s was higher than that in the other scenarios (Figure 5).  
Figure 3: Performance of FORCCHN in simulating the ER, GPP, and NEP of Xishuang Banna forests at different time scales. (**a**) daily scale data; (**b**)monthly scale data; (**c**)annual scale data.  
By comparing the future carbon sequestration potential of Yunnan forest ecosystems under three different emissions scenarios, the carbon sequestration under the SSP1-2.6 scenario was significantly higher than that under the other scenarios. The annual mean values of NEP under the SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios were 133.94, 121.26, and 121.41 gCm\({}^{-2}\).yr\({}^{-1}\), respectively (Figure 4), and the 5-year moving average showed that NEP will peak and show a fluctuating decreasing trend from 2027 to 2040, followed by a rapid decrease in the next 10 years. NEP under SSP5-8.5 was lower than SSP1-2.6  
Figure 4: Interannual variation in carbon fluxes in forest ecosystems from 2020 to 2060.  
Figure 5: Violin plot of carbon fluxes in forest ecosystems from 2020 to 2060. (The tops and bottoms of each ‘box’ are the 25 th and 75 th percentiles of the samples, respectively. The point in the middle of each box denotes the median value. The upper and lower whiskers are the 5 th and 95 th percentiles of the samples, respectively).  
in 2025-2038 and 2043-2058, but higher than the other scenarios in 2060, which results in higher NEP variability in the SSP5-8.5 scenario than in SSP1-2.6 and SSP2-4.5. The reason for this phenomenon was that the GPP growth rate was higher than the ER growth rate in the 2030s under the SSP1-2.6 scenario.