EAST BERLIN, DEC. 7 -- An atmosphere of youthful, 1960s-style rebellion prevails at the Environment Library coffee shop, a gathering place for East Germany's small but growing dissident movement.

Psychedelic paintings cover the walls of the cramped, smoke-filled cafe in a building owned by the nearby Protestant Zion Church. Most male clients sport beards and shoulder-length hair, although a few prefer a punk style.

This year, two themes have dominated talk at the coffee shop: Soviet leader Mikhail Gorbachev's reform program, and the East German government's reluctance to embrace it.

Gorbachev's "new thinking" has emboldened the dissidents and encouraged them to assert themselves more openly in the past two years than at any time since 1983, according to dissident leaders and western diplomats.

Opposition activism has risen particularly since the summer, partly because the authorities were reluctant to crack down during Berlin's much-publicized 750th anniversary and in advance of East German leader Erich Honecker's landmark visit to West Germany in September.

But the authorities moved against the dissidents two weeks ago. They detained several dozen activists, confiscated dissident literature and seized six mimeograph machines and a typewriter in a basement room in the same church-owned complex as the Environment Library. The experience here underlines the tendency implicit in Gorbachev's policy of glasnost, or openness, to encourage increased dissent in Eastern Europe, according to western diplomats and other political analysts.

Here in one of the East Bloc's most regimented states, Gorbachev is more popular with the opposition than with the communist leadership.

"With the change in the Soviet Union, people have much greater hope," Carlo Jordan, 36, an activist and philosophy teacher, said in an interview last week at the Environment Library.

"Perhaps things can change more now than when change was attempted in Poland" by the Solidarity movement in the early 1980s, before Gorbachev came to power, he said.

The dissidents, who prefer to be called "independent activists," have launched newsletters criticizing government policies on the environment, disarmament and human rights.

In an unusual display of public dissent, they paraded in September with banners and placards demanding the right to travel to the West and an end to the military draft. One banner simply bore a quote by Gorbachev saying that "democracy" was as necessary as "air to breathe."

That protest occurred when about 1,000 independent activists joined government-backed participants and foreign groups in an authorized peace march honoring the late Swedish prime minister and disarmament advocate Olaf Palme.

In another sign of increased dissent, pop music fans clashed with police for three straight nights in June when the authorities sought to prevent the youths from gathering near the Berlin Wall to eavesdrop on open-air concerts in West Berlin.

The disturbances, in which scores were arrested, were the most serious in East Germany in nearly 10 years. The youths chanted, "The wall must go!" and "Gorbachev! Gorbachev!"

The East German dissident movement remains tiny and cautious compared to Solidarity. But the increased activism worried the authorities enough to trigger the crackdown on Nov. 24, in which police raided church-owned buildings for the first time since the 1950s.

Between 35 and 40 activists were detained briefly here and in three other cities, dissident leaders said. One of the seized mimeograph machines had been used to produce the Environment Page, one of the more popular dissident newsletters. The other five machines did not work, organizers at the Environment Library said.

Two activists who were caught producing the Environment Page were held for four days before being released. A criminal investigation was begun against them and two others, but their lawyer now says that the charges probably will be dropped.

Air pollution is a sensitive issue in East Germany, where the soft coal burned by electric plants produces a particularly heavy and irritating smoke. Activists established the Environment Library in September 1986 to gather environmental information that they say is suppressed by the authorities.

Police charged that the mimeograph machine seized here also was used to produce the more controversial newsletter Grenzfall, or Borderline Case. The title is a double entendre, referring both to the heavily fortified border between East and West Germany and to a political perspective that tests the boundaries of communist policies.

Environment Library organizers and Grenzfall editors denied that the newsletter was produced in the church building's basement. Grenzfall does not enjoy church patronage.

The dissident movement depends heavily on the protection of East Germany's Protestant Church, which provides the activists with meeting rooms and other logistical support. The church is the only influential organization that is independent of the state here.

Grenzfall, founded in June 1986, prints between 700 and 800 copies of each monthly issue and is produced by the Peace and Human Rights Initiative.

The newsletter includes mild, often humorous criticisms of the government, particularly on travel issues. "It is very difficult to say at the moment what will happen" after the police action, said Peter Grimm, an editor.

Grimm and other analysts noted that the government, despite its open skepticism of Gorbachev's policies, has shown signs of tolerating greater freedoms this year. Authorizations for brief trips to West Germany have risen sharply, and the government-controlled newspapers have grown more willing to publish stories about social problems.