## 4 Results  
### Spatial Zoning in the Su-Xi-Chang Region  
#### 4.1.1 The Collate Partitioned Data  
The year 2018 is selected as the research period in order to avoid inaccuracies caused by inconsistent statistical coverage. Figure 3 represents the spatial distribution of four factors, while Figure 3a is the NPP-VIIRS annual total DN value. Overall, the circular layer characteristic of the center-transition-periphery structure is very prominent. Patches with a large number of high-value nighttime light areas are concentrated in six cities. Additionally, the connection between the patches is strong, exhibiting obvious spatial aggregation characteristics. This distribution coincides with the characteristics of the regional urbanization mode of the urban agglomeration.  
The total value of _GPP_ shows that the Su-Xi-Chang region has an excellent environment background. Apart from water and construction land, _GPP_ in most regions is at a medium-high level. The red area represents the high value of _GPP_ and is mainly located in hilly areas in the southwest and west of the urban agglomeration. Forest and grass vegetation at the periphery have a high level of _GPP_, while water areas have a 0 _GPP_. The edge area with intertwining cultivated and construction lands is located at the intermediate transition zone. The core area of the urban agglomeration is located in the inner region.  
As shown in the map of traffic network density, the spatial distribution of the traffic road network density exhibits a multi-core, indicating that the Su-Xi-Chang region is connected as an accessible whole. In addition, Suzhou, Wuxi, Kunshan, and Changzhou together are seen as the peak traffic area, while road network density in other areas is low. Overall, spatial distribution is hierarchical and extends from the peak area to the lowest area. The blue area represents the area with the lowest traffic network density, namely, the natural ecological one. Medium density represented in yellow is distributed in a ring band around the peak area and has become the transition zone between the core area of the urban agglomeration and the natural ecological area. This \"ring band\" characteristic conforms to the traditional definition of an urban edge area.  
In 2018, the highest annual _LST_ was about 36.46 \({}^{\circ}\)C, the lowest was about 18.46 \({}^{\circ}\)C, and the average about 20.33 \({}^{\circ}\)C in the Su-Xi-Chang region. In combination with the spatial distribution diagram of _LST_, it is evident that the spatial distribution characteristics of _LST_ in the study area are high in the plains and low in mountains and rivers. In addition, the spatial distribution of _LST_ has formed an enormous and continuous integrated _LST_ patch of high value. The low-value _LST_ areas are concentrated in the hilly and mountainous areas in the southwest and the Yangtze River and Tai Lake. Land cover types in these areas are mainly forest vegetation, rivers, and lakes with high specific heat capacity, less human  
Figure 3: Partitioned data; (**a**) The NPP-VIIRS annual total DN value; (**b**) The total value of _GPP_; (**c**) The traffic network density map; (**d**) Spatial distribution of annual mean _LST_.  
activity, and less anthropogenic heat emissions. As a result, these factors together form the spatial agglomeration of low-value \(LST\) areas.