The HANTS-fitted data in the vegetation growing season can improve RSEI accuracy in revealing the spatiotemporal patterns of ecological quality in Yuxi of China

Abstract

Yuxi, a region of active economic development in China's central Yunnan Plateau, is subject to the ecological pressures brought about by rapid urbanization. In order to provide a scientific rationale for making decisions about environmental management, a long-term and accurate methodology for appraising and evaluating the ecological condition is required. Firstly, this study used 30 m-resolution Landsat data to reconstruct four indices, including greenness, wetness, dryness, and heat, during the vegetation growth period in Yuxi from 2000 to 2020 by using the HANTS filtering method. Secondly, we computed the annual RSEI using reconstructed indices to assess ecological quality in Yuxi. Thirdly, through Sen + MK trend analysis, spatial auto-correlation analysis, and geographical detectors on year-by-year RSEI, the spatiotemporal pattern and determinants of Yuxi's ecological quality were revealed. The results showed that: (1) vegetation seasons obviously affect the accuracy of the RSEI, and the data of the vegetation growing season is suggested to construct the RSEI model; (2) HANTS can effectively optimize the ecological indices of constructing the RSEI model, making the missing data filling smoother and more continuous. The reconstructed RSEI and the original RSEI have an absolute difference ranging between − 0.15 and 0.15; (3) the comprehensive ecological quality of Yuxi is moderate according to the RSEI mean value (0.5413), and the ecological quality of mountainous areas is better than that of valleys and plains. Yuxi's ecological quality manifests a clear center-edge pattern. (4) Between 2000 and 2020, the ecological quality of Yuxi exhibited a fluctuation and slightly rising trend as a whole, and the alteration in land utilization patterns was the primary determinant of Yuxi’s ecological quality shift, especially forestry land and impervious surface. Based on Yuxi, a city on the Central Yunnan Plateau, this study can serve as a reference for scientific decision-making regarding sustainable development and ecological protection.