## 3 Results
### Ndvi
#### 3.3.2 The Spatial Variation Characteristics  
The distribution of improved, stable, and degraded vegetation inside ZINNR accounted for 96.93%, 1.11%, and 1.96%, respectively (Table 9). In contrast, outside ZINNR, they are 93.31%, 2.10%, and 4.59%. The vegetation improvement area was 3.62% greater inside than outside, and the vegetation degradation area was 2.63% less inside than outside. As shown in Figure 8a, the area of vegetation improvement in the ZINNR was far greater than the area of vegetation degradation inside and outside. The areas with improved vegetation were predominantly located in the central region of the NNR and the south-east outside the NNR. Areas with slight vegetation improvement were predominantly distributed in the northeast and southwest regions of the NNR and various regions outside the NNR. Areas with stable vegetation were mainly found in the southwest region. In contrast, areas with slight and significant vegetation degradation were primarily located near water bodies and impervious lands.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & & \multicolumn{4}{c}{**Area Percentage**} \\ \cline{4-7} \(\beta\) & **Z** & **NDVI Trend** & \multicolumn{2}{c}{**ZINNR**} & \multicolumn{2}{c}{**MdfNNR**} \\ \cline{4-7}  & & & **Inside** & **Outside** & **Inside** & **Outside** \\ \hline \(\geq\)0.0005 & \(\geq\)1.96 & Significantly improved & 64.17\% & 62.40\% & 39.71\% & 38.88\% \\ \(\geq\)0.0005 & \(-\)1.96–1.96 & Slightly improved & 32.76\% & 30.91\% & 48.64\% & 44.08\% \\ \(-\)0.0005–0.0005 & \(-\)1.96–1.96 & Stable & 1.11\% & 2.10\% & 4.84\% & 5.55\% \\ \(<\)\(-\)0.0005 & \(-\)1.96–1.96 & Slightly degraded & 1.67\% & 4.04\% & 6.74\% & 11.00\% \\ \(<\)\(-\)0.0005 & \(<\)\(-\)1.96 & Severely degraded & 0.28\% & 0.55\% & 0.08\% & 0.50\% \\ \hline \hline \end{tabular}
\end{table}
Table 9: Trend of NDVI of ZINNR, and MdfNNR.  
Figure 7: Inter-annual variation of NDVI in each study area during 2000–2020. ZIIn represents the inside of ZINNR, ZIout represents the outside of ZINNR, ZIInTrend represents the NDVI change trend line inside ZINNR, ZIOutTrend represents the NDVI change trend line outside ZINNR. The same goes for MdfNNR.  
The areas with improved vegetation, stable vegetation, and degraded vegetation in MdfNNR account for 88.35%, 4.84%, and 6.82%, respectively (Table 9). Conversely, outside MdfNNR, they are 82.96%, 5.55%, and 11.49%. The improved vegetation area was 5.39% greater inside than outside, and the degraded vegetation area was 4.68% less inside than outside. As shown in Figure 8b, the area of vegetation improvement was far greater than the area of vegetation degradation, whether inside MdfNNR or outside. Areas of notable vegetation improvement were predominantly situated in the southwest, whereas areas of slight improvement and stable vegetation were more dispersed. Regions with minor vegetation degradation were primarily found near roads, and areas with severe vegetation degradation were chiefly located near impervious land.  
The time series analysis comparing the two PAs shows that ZINNR has a higher percentage of areas with improving NDVI trends than MdfNNR. Specifically, the percentage is 8.59% higher in ZINNR. For significantly improving trends, ZINNR has 24.46% more area  
Figure 8: Theil-Sen change trend and Mann–Kendall test of NDVI. (**a**): ZINNR, (**b**): MdfNNR.  
than MdfNNR. For slightly improving trends, ZINNR has 15.88% less area than MdfNNR. On the other hand, the percentage of areas with degrading NDVI trends is 4.86% lower in ZINNR than in MdfNNR. For severely degrading trends, ZINNR has 0.06% more area than MdfNNR. For slightly degrading trends, ZINNR has 6.96% less area than MdfNNR. However, the percentage of areas with stable NDVI is 3.45% lower in ZINNR than in MdfNNR, indicating relatively stable NDVI in MdfNNR. In summary, the overall NDVI condition is better in ZINNR compared to MdfNNR.