Unveiling the spatio-temporal patterns of vegetation growth influenced by diverse urban intensity gradients

Urban vegetation plays a pivotal role in mitigating environmental challenges, yet its growth is influenced by both positive and negative impacts of urbanization. The spatio-temporal dynamics of these dual effects, particularly the indirect benefits, remain insufficiently explored. Taking Chengdu as a case study, we applied two complementary urban intensity gradients, a conceptual (local) and a physical (rural-urban) approach, to quantify urbanization's impacts on vegetation, as measured by net primary productivity (NPP), and to investigate temporal and spatial variations. Both approaches indicate that urbanization initially has a negative effect on vegetation, but transitions to positive impact as overall urban intensity increases. The conceptual gradient analysis demonstrates a marked temporal increase in positive indirect effect, rising from 0.99 % in 2000 to 49.51 % in 2010 and reaching 85.15 % in 2018, highlighting significant temporal variability in vegetation enhancement. Meanwhile, the physical gradient reveals pronounced spatial heterogeneity, with stable and prominent indirect compensation effects in suburban areas compared to urban cores. These findings deepen the understanding of urban vegetation dynamics and provide valuable guidance for targeted vegetation management and sustainable urban planning.