Spatiotemporal Evolution of Urban Expansion in Zhengzhou City: Impacts on Ecological Environment Quality

As the core growth pole of the Central Plains Urban Agglomeration, Zhengzhou's rapid urbanization has significantly disrupted regional ecological security patterns. This study integrates multi-temporal Landsat remote sensing data (2000-2020) to develop an Improved Remote Sensing Ecological Index (IRSEI) that synthesizes fractional vegetation cover (FVC), normalized difference built-up index (NDBI), and land surface temperature (LST). Combining a Geographically and Temporally Weighted Regression (GTWR) model, we systematically quantify the ecological response mechanisms to urban expansion across 12 counties/districts in Zhengzhou. Results reveal three key insights: First, spatial patterns exhibit “monocentric dominance-gradient differentiation,” with the southeastern plains (Zhongmu County, Xinzheng City) experiencing an annual expansion intensity of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{8. 2 1 \%}$</tex>, driving increases of 35.6% in patch density and 59.4% in landscape shape index, while the northwestern ecological barrier zone (Dengfeng City, Xingyang City) maintained a maximum patch index above 0.62 under ecological conservation redline constraints. Second, IRSEI evolution displays a “rise-then-decline” trend, with its mean value fluctuating from 0.469 (2000) to 0.487 (2020). Ecological quality improved by 12.6% in northwestern mountainous areas, whereas the southeastern core zone (Jinshui District, Zhongyuan District) suffered a 7.3% IRSEI decline due to synergistic heat island effects and construction land sprawl. Third, GTWR modeling identifies expansion intensity and landscape morphology as dominant drivers, where a 1-unit increase in southeastern urban expansion intensity reduces IRSEI by 0.38, with landscape fragmentation explaining 68% of ecological degradation. This research provides a quantitative basis for balancing territorial spatial development and ecological conservation in the Zhengzhou Metropolitan Area, and the IRSEI-GTWR framework offers a novel methodology for sustainable urban agglomeration assessments.