About 200 monks sit cross-legged in a shady courtyard at the 585-year-old Sera Monastery and loudly debate Buddhist scriptures on a sunny afternoon.
Outwardly, Sera is one of Tibet's most important and best-preserved Buddhist centers. But within, much has changed under communist rule, the result of strict controls on religion that activists say endanger the future of Tibet's unique Buddhist culture.
Under 1994 guidelines from China's Communist Party, the government limits numbers of monks, restricts religious teaching and requires monks to attend political classes and denounce the Dalai Lama, the leader of their faith, according to a report last month by a foreign monitoring group.
Sera, once home to more than 5,000 monks, now has 550.
"The religion is under more threat in its homeland than ever before," said Kate Saunders, one of the authors of a report from the International Campaign for Tibet.
Buddhism is part of nearly every aspect of daily life for ordinary Tibetans. China views this devotion to the religion and the Dalai Lama, who lives in exile in India, as a threat to its supremacy.
Communist troops took over Tibet in 1951 and Beijing contends the Himalayan region has been Chinese territory for centuries. Many Tibetans say they were effectively independent for much of that time.
Thousands of Tibetan monasteries and temples were destroyed during the ultra-leftist political violence of the Cultural Revolution of 1966-76, along with key religious texts.
Chinese leaders accuse the Dalai Lama, who fled in 1959 after a failed uprising, of pursuing independence. He says he wants only autonomy for the region to preserve its language and culture.
Because of the pressure, the Dalai Lama is "more popular than ever," said Robert Thurman, a former Tibetan Buddhist monk who is a professor at Columbia University in New York. "He has become a symbol of freedom to all Tibetans."
The Chinese government "is trying to suppress Tibetan Buddhism in more subtle ways than in the past, but just as fiercely," Thurman said.
According to the International Campaign for Tibet report, official controls are threatening knowledge of Tibetan Buddhism's esoteric doctrines, lowering the quality of religious teaching by limiting classroom time for young monks and blocking other monks and nuns from traveling to receiving instruction.
The restrictions are a topic of enormous sensitivity with officials and monks alike.
"I can say that there is absolutely no effect on Buddhism, no diluting of the religion going on," Xiao Bai, deputy mayor of Lhasa, the Tibetan capital, said at a news conference arranged by the government for foreign reporters. "We are trying to restore what was undermined or destroyed during the Cultural Revolution."
Asked about the Dalai Lama, Xiao read from a statement that denounced him as a "splittist" and wouldn't answer questions. Other officials at the event refused to disclose details on monastery quotas and patriotic education classes.
According to official Chinese sources, Tibet has 1,700 temples and monasteries and 46,000 clergy.
Zhao Yuyuan, deputy director of nationality and religion for Lhasa's city government, said he did not wish to reveal how many Tibetans applied to be monks every year and how many are accepted. He would only say that candidates must "love the country, love patriotic Buddhism ... and have a good cultural education."
At Jokhang, Tibet's most sacred temple, Thup Ten, a monk of 20 years, insists there have been no changes.
"It's the same practice before and now," he told reporters under the gaze of government officials.
Togme Soba, a 31-year-old monk at Sera, talked readily about his daily routine and curriculum. But when asked about patriotic education and the Dalai Lama, he said: "It's best you don't ask me this."
Monks are under pressure to endorse a boy chosen by Beijing in 1995 as the reincarnation of the Panchen Lama, the No. 2 figure in Tibetan Buddhism. Another boy chosen by the Dalai Lama was taken into custody by security forces three days after his identity was publicly revealed. The boy, Gedun Choekyi Nyima, has not been seen since.
On Saturday, Xiao said he is doing well in school and is "in good health and leading a normal and happy life," but refused to say where. Xiao said the boy has not been made available to reporters so that his life can be "normalized" at his family's request.
Though the Dalai Lama is long absent, pilgrims who visit the Potala and Norbulinka Palaces — his former winter and summer homes — prostrate themselves before his throne.
"Devotion to the Dalai Lama is probably the one thing that binds virtually all Tibetans together," Saunders said by phone from London.
"We want him to come back," said a 30-year-old Sera monk. "Someday we will get the results we have been shouting for."