It's party time at "People's Perch."

The crew of protesters who climbed into the oak trees next to UC Berkeley's Memorial Stadium the day of the Big Game in 2007 are celebrating the anniversary of their arboreal blockade today, reaffirming their vow to stay in the foliage and protect the trees from university bulldozers.

"We're following our hearts. We're serving a righteous cause," said Shem, 25, one of the core group of a dozen or so tree-sitters who've rotated in and out of the oaks. As a rule, the tree-sitters don't give out their real names. "People call us crazy monkey hippies, but this is the greatest thing I've ever done. I feel like I'm truly alive."

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The protest has become what may be the longest-running urban tree-sit in the world, according to Karen Pickett of the Bay Area Coalition for the Headwaters, which monitors environmental protests internationally. It's also become an inspiration and training ground for those who want to launch other tree-sits, she said.

"Quite literally, it's taught people the ropes," she said. "It's so accessible to the public and so visible to the community that it's become iconic in the ecological movement."

The tree-sitters are hoping to protect the oaks, redwoods, laurels and other trees in the grove from a University of California plan to build a $125 million sports training center. The university has said it would plant two saplings and one mature tree for each one that's removed. All but two or three of the trees were planted after the stadium was built in 1923, but at least one of the trees, which protesters call the Sentinel Oak, is more than a century old.

To encourage the protesters to climb down, the university has surrounded the grove with two chain-link fences topped with barbed wire, shines floodlights on the tree houses throughout the night, and has secured a judge's order declaring the protest illegal. UC police have issued more than 200 citations and made dozens of arrests. When arrested, protesters face five days in jail and a $1,000 fine - one sitter has been arrested nine times and spent some earthbound time in Alameda County's Santa Rita Jail.

An Alameda Superior Court judge is expected to rule by early January on the fate of the oak grove.

The university, meanwhile, is increasingly fed up with the scene, which some call "People's Perch" after the university's decadeslong trouble at People's Park.

"Whatever the outcome of the court case, we'll obviously abide by the law," Vice Chancellor Nathan Brostrom said Friday. "Unfortunately, we don't have a reciprocal commitment from the people in the trees. They need to come down, regardless of the outcome of the case."

One of those who has been arrested is Midnight Matt, 51, who's provided ground support from Day One at the protest. He said he is undeterred by the beefed-up law enforcement and, like the other protesters, won't leave until the university promises to build its training center elsewhere.

"I think the university is acting very arrogantly and needs to be checked," he said Friday morning, after staying up all night providing security and provisions at the grove. "We're staying with it, no matter what."

The protest may soon reach a climax if the judge decides the university can build the training center. UC officials have said they'd begin construction immediately, which would almost certainly lead to a confrontation with the tree-sitters.

Both sides say they want to avoid violence.

"The only thing that would get the protesters down is if the university decides to look at alternate sites," Pickett said. "Nothing else."

Price of protest

UC Berkeley officials say the tree-sitters have cost the school $367,000 since the protest began one year ago:

$100,000

Police staffing

$125,000

Private security

$37,000

First fence around protest site

$80,000

Second fence around protest site

$25,000

Equipment, cleanup and other costs

Source: UC Berkeley

How protesters will mark anniversary

Here is how tree-sitters will celebrate the first anniversary of their protest today:

-- 11:30 a.m.: news conference by attorneys Tony Serra, Dennis Cunningham and others who say UC police are intimidating the protesters and their supporters.

-- Noon to 6 p.m.: rally with music, dancing, speeches, face painting, poster-making.

-- 1 p.m. news conference with Save the Bay co-founder Sylvia McLaughlin, Native American activists, Country Joe McDonald and UC Berkeley students.