 If you look closely at Ponderosa pine forests almost anywhere, you will see evidence of fire. These scars are caused by ground fires that periodically sweep through this forest, fires that move through so rapidly that they may damage a portion of the tree trunk, but do not generally kill the tree. Mature Ponderosa pine have several features that allow them to survive ground fires. One thing is this thick bark that protects the tissues that conduct food and water and accomplish growth in the plant. As they get older, Ponderosa pine naturally lose their lower branches, which makes it harder for the fast-moving ground fires to reach the crown. Fire is a natural, recurring aspect of the ecology where Ponderosa pines grow. Tree ring data and historical photos such as these from Custer's 1874 expedition indicate that fire was then frequent in the Black Hills. The natural result was a pine savanna, widely spaced trees with grasses and wildflowers on the forest floor. You can see in this photo of the same spot that pine trees have spread to new areas and the trees are more numerous and closer together. There are more small and medium-sized trees that can carry fire to the crowns of mature trees and kill them. Selective logging accomplishes many of the same ecological benefits in Ponderosa pine forests without fire by thinning them and reducing the fuel load. Both fire and human management have a role in keeping our forests healthy. I'm Gene Gade from the University of Wyoming Cooperative Extension Service.