The city is preparing to remove 20 trees that are dead or dying in Copley Square. The Boston Parks and Recreation Department and the Friends of Copley Square said at a public meeting Wednesday that the trees, all London Plane trees and all infected with a canker stain fungus, are scheduled to be removed starting early next week. The section of the park closest to Boylston Street will see the most dramatic change when the trees are removed, city officials said. A total of 16 trees will be removed near Boylston Street, and another four will be removed in an area close to St. James Avenue. All but two of the trees will be replaced with new species of trees. The two that will not be replaced are located in an area of high foot traffic and activity, near St. James Avenue.