Fig. 9: Altitudinal frequency distribution of SRSCs from the Southern Dynasties and the early Ming period.

This figure presents two histograms comparing the elevation preferences of SRSCs from a the Southern Dynasties and b the early Ming period. The x-axis represents elevation (altitude in meters), while the y-axis indicates the quantity of SRSCs within each altitude range. Panel (a) shows that SRSCs from the Southern Dynasties are concentrated in low-altitude zones, particularly between 9–18 m, suggesting a strong preference for flat, river-adjacent terrain. In contrast, panel b reveals that SRSCs from the early Ming period shift slightly toward higher elevations, with most sites distributed between 13 and 43 m, indicating a broader altitudinal tolerance and potential changes in site selection criteria over time. These frequency distributions reflect evolving burial practices and highlight the influence of geographical and cultural factors in the spatial planning of spirit roads across different dynastic periods.