The researchers studied vegetation coverage in Ningxia from 1999 to 2009. They found that vegetation was highest in the Liupanshan Mountains and Yellow River irrigation areas, and lowest in the middle arid zone. Overall, vegetation coverage increased in most areas during this time. The study showed that precipitation fluctuations and temperature increases were key factors influencing vegetation growth. In areas with more rain, vegetation tended to be higher, while warmer temperatures promoted crop growth and increased vegetation coverage.