LHASA, May 31 (Xinhua) -- Leaning on the grassland, their elbows and knees on the ground, villagers from Biru County in southwest China's Tibet Autonomous Region search for a precious gift of nature -- caterpillar fungus.

Biru County, at an altitude of over 4,500 meters, is an ideal place to harvest high-quality caterpillar fungus. The fungus has a long history in traditional Chinese medicine. It is widely believed to be a precious medicinal mushroom with health benefits.

China is the largest caterpillar fungus producer in the world, with production bases distributed across the Tibet Autonomous Region and the provinces of Qinghai, Sichuan, Gansu and Yunnan.

This year, more than 50,000 locals made the trek up the hills in Biru County in May, which is the prime picking period.

Qime Garde, 43, is among the locals participating in this year's harvest season, which lasts some 45 days. Holding a hoe in one hand, she searches carefully for signs of the fungus, scanning the grassland for dark brown sprouts.

"I have dug up 20 fungi today, a fairly good harvest," she said.

Local pickers like Qime Garde always backfill the soil immediately after digging up a fungus. Backfilling is a method aimed at protecting the grassland on the hill and providing opportunities for the fungus to grow in the following years.

Authorities in Biru County also charge fungus pickers a fee for ecological restoration and grassland maintenance, preservation and management.

In 2021, the output of caterpillar fungus in the city of Nagqu, which administers Biru County, was 24,200 kilograms, with an output value of approximately 3 billion yuan (about 450 million U.S. dollars). In addition to sales, the fungus has also brought to Nagqu more tourists who look for a different travel experience.

Baqen County, which is about 260 kilometers from Biru, launched a caterpillar fungus harvest festival last year. The second iteration of the festival is being prepared this year.

Norbu Samdrup, a fungus picker, said the booming business has helped raise his family income.

In his tent by the hill where he picks the fungus, the rain has just stopped. "More caterpillar fungus will grow from the soil after the rain," Norbu Samdrup said while counting his haul for the day. "I believe the harvest tomorrow will be even better."