## 2 Materials and Methods
### Evaluation of the Indicator of Carbon Sequestration Ability  
In this study, the ecological nodes represent the vegetation ecosystems in their locations. Researchers usually use GPP or NPP to express the carbon sequestration capacity of vegetation. GPP represents the ability of green plants to fix CO\({}_{2}\) from the atmosphere through photosynthesis, while NPP is GPP minus the part consumed by autotrophic respiration [46]. In forest or grassland ecosystems as a whole, the amount of CO\({}_{2}\) excreted through soil respiration may be higher than that fixed by green plants. In addition, the carbon changes caused by external disturbances (e.g., forest fires) to the ecosystem need to be considered. Therefore, we believe that NBP (net biome productivity) better reflects  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Resistance Type** & **Factor** & **Level** & **Ecological Resistance Value** \\ \hline Topography and landform & DEM & \textless{}1000 m & 1 \\  & & 1000–1500 m & 3 \\  & & 1500–3000 m & 5 \\  & & 3000–4500 m & 7 \\  & & \textgreater{}4500 m & 9 \\  & Slope & \(\textasci{}0.2\)\(\textasci{}0\) & 1 \\  & & 2–5\(\textasci{}0\) & 3 \\  & & 5–8\(\textasci{}0\) & 5 \\  & & 8–14\(\textasci{}0\) & 7 \\  & & \textgreater{}14\(\textasci{}0\) & 9 \\ Vegetation cover & NDVI & \textless{}0.2 & 9 \\  & & 0.2–0.4 & 7 \\  & & 0.4–0.6 & 5 \\  & & 0.6–0.8 & 3 \\  & & \textgreater{}0.8 & 1 \\ Hydrology & MNDWI & \textless{}0.05 & 9 \\  & & \textasci{}0.05–0.02 & 7 \\  & & \textasci{}0.02–0.02 & 5 \\  & & 0.02–0.08 & 3 \\ Density & Residential density & \textgreater{}0.08 & 1 \\  & & 0.08–0.24 & 3 \\  & & 0.24–0.44 & 5 \\  & & 0.44–0.66 & 7 \\  & & \textgreater{}0.66 & 9 \\ Road network & \textless{}0.02 & 1 \\ Density & 0.02–0.06 & 3 \\  & & 0.06–0.1 & 5 \\  & & 0.1–0.16 & 7 \\  & & \textgreater{}0.16 & 9 \\ Water network & \textless{}0.17 & 9 \\ Density & 0.17–0.43 & 7 \\  & & 0.43–0.84 & 5 \\  & & 0.84–1.53 & 3 \\  & & \textgreater{}1.53 & 1 \\ Railway network density & \textless{}0.003 & 1 \\  & & 0.003–0.01 & 3 \\  & & 0.01–0.02 & 5 \\  & & 0.02–0.04 & 7 \\  & & \textgreater{}0.04 & 9 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Ecological resistance factor evaluation system.  
the overall net carbon sequestration capacity of vegetated ecosystems [47]. The calculation formula of NBP is  
\[NBP=GPP-Ra-Rh-NR, \tag{3}\]  
where \(GPP\) represents the gross primary productivity, \(Ra\) represents the autotrophic respiration consumption, \(Rh\) is the heterotrophic respiration consumption (soil respiration), and \(NR\) is the photosynthetic product consumed by non-respiratory metabolism.  
NBP is a vegetation productivity concept applied at the landscape scale, and its unit is g-C m\({}^{-2}\).year\({}^{-1}\), with positive or negative values. Actually, NBP is numerically the value of carbon sources or sinks in terrestrial ecosystems in global change studies. A positive NBP value indicates that the vegetation ecosystem as a whole is a carbon sink, fixing more carbon per unit time than it emits. Conversely, a negative NBP value indicates that the ecosystem as a whole is a carbon source, fixing less carbon per unit time than it emits. The magnitude of the absolute value of the NBP value indicates the strength of the net sequestration or emission of CO\({}_{2}\) by the vegetated ecosystem, i.e., the strength of the carbon sequestration capacity [46].