Thousands of students and soldiers rose early to plant trees amid a sandstorm alert on Wednesday, the 28th Tree-planting Day in Beijing's neighboring Inner Mongolia Autonomous Region, local officials said.

The planting day was part of an ongoing effort by Beijing and several nearby provinces to improve the air quality. Inner Mongolia has long been a major source of sandstorms in the capital area.

The regional meteorological observatory posted an orange sandstorm alert on Wednesday, saying that a sandstorm would hit the region in 12 hours or has already appeared, after a sandstorm moved into neighboring Mongolia on Wednesday morning.

Inner Mongolia has been fighting desertification for many years. About 1.2 billion trees have been planted over the past 27 years, representing 256 million person-days of work. The region now has 312 million mu (about 20.8 million hectares) of forest, covering 17.57 percent of the land area, officials said. The percentage of forest cover will rise to 20 percent by 2010 and 23 percent by 2020, they said.

Planting efforts mean that forest acreage has increased by 11 million mu, up 3 percent, and desert area reduced by 38 million mu, down 22.16 percent, over the past eight years, according to local statistics.

The region has also tamed 21.72 million mu of grassland and planted 32.5 million mu of forest since the 1990s, statistics show.

Dusty weather and sandstorms are expected to hit northern provinces from the northwest Xinjiang Uygur Autonomous Region to the northeast provinces of Liaoning and Jilin in the next two days, said the China Meteorological Administration on Tuesday.