I'm looking for academic works on—or containing something on this topic—the role of trees & forests in human societies. For instance: forests as a resource (for example sawmills), trees have been used as landmarks, places of political gatherings, hanging trees, etc.
You may be interested in Conrad Totman's The Green Archipelago: Forestry in Pre-Industrial Japan.
Professor Totman raises the critical question of how Japan’s steeply mountainous woodland has remained biologically healthy despite centuries of intensive exploitation by a dense human population that has always been dependent on wood and other forest products. Mindful that in global terms this has been a rare outcome, and one that bears directly on Japan’s recent experience as an affluent, industrial society, Totman examines the causes, forms, and effects of forest use and management in Japan during the millennium to 1870. He focuses mainly on the centuries after 1600 when the Japanese found themselves driven by their own excesses into programs of woodland protection and regenerative forestry.
Japan's case is absolutely fascinating because they were on the verge of ecological catastrophe in the late 1500s, with over-use of the forests, and managed to come back from that through some of the earliest state/community comprehensive forestry management programs in the world. (If you've ever seen Miyazaki's "Princess Mononoke, btw, this is the historical context of that film, with forestry exploitation and management portrayed in supernatural terms.) Given that forest management is now a global issue, this Japanese history is particularly interesting.