Beyond Homogenization: Spatio-Temporal Dynamics of Urban Vitality and the Nonlinear Role of Built Environment in Shenyang’s Historic Urban Area

The vitality dynamics of historic urban areas under high tourism pressure and their underlying mechanisms remain not fully understood, posing a challenge to sustaining their uniqueness against homogenized redevelopment. To explore this issue, this study utilises human mobility data and an XGBoost-SHAP model to examine the spatio-temporal dynamics of block-level vitality and to uncover the nonlinear effects of built environment factors in Shenyang, China. The results indicate that: (1) Diverging from the commuting patterns of general urban areas, the vitality of historic urban areas presents unique spatio-temporal shifts, transitioning from commercial centers on weekdays to a commercial-cultural mix during holidays. (2) The determinants of vitality vary temporally, shifting from accessibility-oriented (subway) on weekdays to heritage-oriented (state historic sites) during holidays. (3) By applying the ‘Three-Factor Theory’ from satisfaction research to decode nonlinear effects, the study classifies factors into Performance (functional density), Basic (proximity to water bodies), and Excitement (distance to subway and state historic sites). The findings guide urban renewal to prioritize systemic and sustainable vitality across the historic urban areas rather than maximizing vitality in specific locations.