Native American tribes are legal entities with their own property rights that look somewhat like sovereign inholdings within the borders of the U.S. Some of their land borders U.S. Forest land, so there is a need to coordinate. They also rely on some centralized services of the Forest Service, like fire fighting, that they struggle to capably provide by themselves.
The Office of Tribal Relations (OTR) serves as a single point of contact for Tribal issues and works to ensure that relevant programs and policies are efficient, easy to understand, accessible, and developed in consultation with the American Indians and Alaska Native constituents they impact.
From Forest Service-----
Tribal Relations Specialists play a critical role in the government-to-government trust responsibility that is crucial to the health and sustainability of many of our nation’s most treasured landscapes. They serve as the point of contact for American Indian Tribes; work with Tribal Councils, Tribal Leaders, and officials of other agencies; and serve as partnership coordinators for programs involving collaboration and consultation with American Indian Tribes.
Many tribes are treated as mini nations within the US with their own treaties negotiated between them and the US. They often border Federal land. They often have waterways and water rights that impact/restrict/are tied by treaty to federal land waterways. They may also have shared animal management plans. You kind of need someone who understand the treaties and policies of the nations you work with on a daily basis.