Ecological Quality Changes and Influencing Factors of Land-Cover Ecological Units in Jiaxing City Based on Temporally Enhanced RSEI

Reliable interannual ecological quality comparisons are essential for regional management, but conventional remote sensing ecological index (RSEI) assessments may be affected by year-specific normalization and principal component analysis (PCA). We developed a temporally enhanced RSEI (tRSEI) for Jiaxing City using Landsat observations from six years (2000, 2005, 2010, 2015, 2020, and 2025), integrating full-time-series standardization, unified PCA, and full-time-series normalization. We compared tRSEI with conventional RSEI, assessed cropland, forestland, grassland, and non-vegetated areas, and identified influencing factors using an optimal-parameter geographical detector. The first principal component explained 72.78% of the variance, and tRSEI closely agreed with conventional RSEI at the pixel scale (R2 = 0.9789–0.9991). tRSEI retained expected relationships with greenness, wetness, heat, and dryness. Ecological quality generally declined, fluctuated, and then recovered. Mean tRSEI values were 0.6760 for cropland, 0.5164 for forestland, 0.4316 for grassland, and 0.3457 for non-vegetated areas. Cropland showed the highest ecological quality but slight degradation, forestland the greatest temporal stability, and non-vegetated areas the greatest interannual variability. Nighttime lights, GDP, and population density were major explanatory factors, with population density becoming more influential over time. These findings support temporally consistent ecological assessments and differentiated management.