## 3 Results
### Spatial-Temporal Change of Vegetation Coverage  
The annual average FVC in Harbin ranges between 35.57%-47.41%, and vegetation coverage varies regionally (Figure 7a). The overall spatial distribution of FVC in Harbin exhibits that the urban fringe region is obviously higher than the central region. The average FVC in the Nangang district is 0.39, consisting mainly of extremely high grade and low grade, occupying 40.14% and 22.68% of its area, respectively. The highest average FVC in the Pingfang district is 0.81, which is mainly extremely high grade and high grade, taking up 49.46% and 23.56% of its area, respectively. Overall, the very high grade accounts for  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **2005** & **2010** & **2015** & **2020** \\ \hline SHDI & 1.0285 & 1.0915 & 1.0927 & 1.0743 \\ SHEI & 0.574 & 0.6092 & 0.6098 & 0.5996 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Changes in the landscape-level metrics in Harbin between 2005–2020.  
Figure 6: Changes in landscape pattern metrics of (**a**) PLAND; (**b**) NP; (**c**) PD; (**d**) LSI; (**e**) ED; (**f**) DIVISION from 2005 to 2020.  
the largest area proportion, which fills about 50.98% of Harbin's area, mainly distributed in the Songbei and Daowai districts (424.22 km\({}^{2}\) and 322.98 km\({}^{2}\)), while it has the least distribution in the Pingfang district (48.85 km\({}^{2}\)).  
Figure 7: The average values (**a**) and coefficient of variations (**b**) for vegetation coverage in Harbin from 2004 to 2020.  
The coefficient of variation reflects the discrete degree and temporal variability through time in 2004-2020 (Figure 7b), which was divided into four classes using the geometrical interval classification method, including very stable (0\(\sim\)0.2), stable (0.2\(\sim\)0.4), unstable (0.6\(\sim\)0.8), and very unstable (0.8\(\sim\)1.0). The spatial pattern of the coefficient of variation exhibits that the vegetation in the study area is stable overall, but fluctuates in the local area. The under stable class (\(Cv<0.4\)) accounts for 86.54% of Harbin's area, which is mainly distributed in the Songbei and Daowai districts. The unstable class (\(0.6<Cv<0.8\)) is distributed mainly in the Daoli and Songbei districts, accounting for 9.46% of Harbin's area. The area with a high fluctuation class (\(Cv>0.8\)) is concentrated in the urban region in the Daowai and Songbei districts, accounting for 4.0% of Harbin's area.  
Combining the linear regression slope method and F test, the spatial pattern and variability of vegetation coverage can be described to reflect the FVC trends. From 2004 to 2020, the variation trends of FVC ranged from \(-0.05\)-\(0.06\). A decreasing trend in vegetation cover was noted in most areas of Harbin (Figure 8), with an extremely significant decrease in about 142.78 km\({}^{2}\), accounting for 5.85% of Harbin's land (\(p<0.01\)). Insignificantly decreased vegetation coverage (\(p>0.05\)) accounted for the largest area (1281.26 km\({}^{2}\), approximately 52.47%), and was more evenly distributed in each district, taking up about half of each district's land. In the contract, the regions with increased vegetation coverage only accounted for 31.53%. The regions where FVC significantly increased comprise only 7.48% of Harbin's area (\(p<0.05\)), which was mainly found in the southern part of the Songbei and northern Daowai districts, and least in the Nangang district. Additionally, the stable vegetation coverage change area of 3.01% was mainly distributed in the main urban area, with an area of about 73.44 km\({}^{2}\). In general, most regions exhibited insignificant FVC changes, accounting for 76.51%. Significant changes were mainly found in the interior of the Pingfang district and along the Songhua river in the Daowai district (Figure S1).