[Dynamic monitoring of ecological environment in loess hilly and gully region of Loess Plateau based on remote sensing: A case study on Fuxian County in Shaanxi Province. Northwest China].

Based on the principal component analysis (PCA), four ecological evaluation indicators including vegetation index, wet index, land surface temperature and soil index were combined to evaluate the ecological environment quality of Fuxian County in hilly and gully area of Loess Plateau from year 1995 to 2014. The results showed that the RSEI integrated RS and PCA method could reveal regional ecological changes objectively and quantitatively. The level of overall regional ecological status in Fuxian County was good with a high vegetation fraction and rich biodiversity. The synthetical ecological environment quality index increased from 3.17 to 3.53 indicating the ecological environment had been improved greatly in recent 20 years. The area with best ecological environment quality was located in Niuwu town. The magnitude of change increased progressively from northwest to southeast, and the biggest change occurred in Jiaodao and Nandaode towns. From 1995 to 2014, the areas with decreased and increased ecological environment quality were 16.7% and 42.7% of the study area, respectively, and the improved regions were mainly distributed in plateau and hilly area in the center, rocky low mountainous area in northeast and the Ziwuling Nature Reserve area in southwest of the county.