The Sudbury Valley Trustees and the city’s Conservation Commission are holding an informational presentation and a site visit this week to detail a land stewardship project aimed at restoring pitch pine and scrub oak barrens to the Desert Natural Area in Marlborough and Sudbury. The 12-acre portion of the larger ecosystem area involves land owned by the Sudbury Valley Trustees in Memorial Forest and Marlborough conservation land. The first phase of the project will involve clearing small- and medium-sized trees and all shrubs from the area, followed by a prescribed burn. A session describing the project will be held from 7 to 9 p.m. Thursday in the Assabet River National Wildlife Refuge Visitors Center, 680 Hudson Road in Sudbury. Also, a site walk will be held from 10 a.m. to noon Saturday, beginning in the parking lot at Concord Road and Hemenway Street in Marlborough.