The plan would mean cutting down the oak grove where protesters have been perching for months.
School officials say one female tree-sitter allegedly bit an arborist and was taken into custody by police.
Authorities say they won't try to yank protesters out of the trees, but they've begun sending in teams to cut supply lines and dismantle some living structures.
A campus spokesman says "the university has been tolerant and that tolerance is coming to an end," adding "we're really hoping that at some point there'll be an outbreak of common sense."
