LHASA, June 18 (Xinhua) -- Ali Prefecture in southwest China's Tibet Autonomous Region will invest over 70 million yuan (around 11 million U.S. dollars) on a tree planting project this year, local authorities said Monday.

The project aims to plant trees on 2,267 hectares in the prefecture, according to the local forestry bureau.

With an average altitude of more than 4,500 meters, Ali Prefecture has a harsh natural environment. Residents have long been troubled by sand, wind and drought.

Tree planting projects were launched in the area in 1970s and 1980s. The environment has improved in recent years with more funding and effective measures undertaken such as introducing cold- and drought-resistant tree varieties.

Between 2012 and 2017, over 100 million yuan was invested to plant over 10 million trees in the prefecture.

The Shiquanhe Basin is a key battlefield against desertification. Statistics show that the average annual precipitation in the basin has increased to 138 millimeters from 73 mm in 1990s.

Nyima Phuntsog, an official with the bureau, said that the survival rates of many tree species, such as rose willow, have exceeded 80 percent thanks to measures including nutrient solution injections and heat preservation cotton wrapping.

"The next step is taking good care of these trees to make them survive longer," Nyima Phuntsog said.