Ecological potential–productivity mismatch in complex-terrain cities: NPP dynamics within TARSEI-derived high-potential areas in Hangzhou, China

High ecological potential areas are widely used to guide ecological protection, but their vegetation productivity function may not change consistently with their spatial extent. This issue is important in complex-terrain cities, where mountains, plains, and urban expansion create strong spatial heterogeneity. Taking Hangzhou, China, as a case study, this study applied the previously developed Terrain-Adjusted Remote Sensing Ecological Index (TARSEI) to identify TARSEI-derived high ecological potential areas (HEPAs) across six spring and summer periods from 2013 to 2025. CASA-estimated net primary productivity (NPP) was used to examine productivity dynamics and HEPA-NPP coupling/mismatch, with MOD17 GPP used for relative consistency assessment. HEPAs were mainly concentrated in the southwestern mountains, where high-potential zones covered 64.1% of the region on average, compared with 25.0% in the northeastern plain and urban region. From 2013 to 2025, HEPAs first declined and later partly recovered, while the main ecological cores remained stable. In summer, HEPA area decreased by 17.41%, whereas mean NPP increased by 4.94%. A larger HEPA area did not always mean higher NPP per unit area. CASA-estimated NPP showed strong temporal consistency with MOD17 GPP ( r = 0.93). The results indicate that ecological potential and vegetation productivity intensity are related but non-equivalent, suggesting that both indicators should be considered when prioritizing conservation in complex-terrain cities.