The researchers used satellite data to study how different types of grasslands in northern Xingjiang changed over time. They looked at five types of grasslands and found that the Enhanced Vegetation Index (EVI) values were lower than the Normalized Difference Vegetation Index (NDVI) values. The EVI values changed similarly to NDVI values, but EVI was more stable in some grasslands. Overall, the study showed that EVI was lower but steadier than NDVI in most grasslands studied.