LOCHIEL, Ariz. — Federal agents dismantled a protest encampment in the San Rafael Valley on Monday, arresting 10 people and cutting down a cottonwood tree activists estimated was about 200 years old. The protesters had spent more than two months occupying a stand of four cottonwoods near the border, where a proposed second border wall would pass. Conservation advocate Russ McSpadden of the Center for Biological Diversity said some demonstrators remained in the trees for 71 days. Video of the operation shows agents surrounding a tree as a crew used a cherry picker to remove a protester. Activists said the tree was cut down shortly afterward. One protester described about 50 masked federal agents entering the camp, which activists said was on private property. Protesters also questioned how agents were identified, saying some wore tape over their badges. Some people arrested had been released by Tuesday, while others remained in custody, according to activists. The confrontation is part of broader opposition to the Trump administration’s plans for a second border wall in southern Arizona. Activists said demonstrations would continue; on Tuesday, one protester was in a cottonwood on the Mexican side of the border.