Timber harvesting not only provides the resource for a broad variety of wood products but it can also be a valuable management tool for maintaining a healthy population of trees that can resist insects and diseases. Forest Service scientists at the agecny's Rocky Mountain Research Station are working with other scientists to investigate the short- and long-term resiliency of the understory vegetation of ponderosa pine forests to a variety disturbances associated with timber harvest.They chose the Black Hills National Forest to conduct their research given its long history of timber harvest. Its first timber sale occurred in 1899 and since then, all land suitable for timber harvest has been logged one-to-four times. Using established study sites in active timber cutting units, scientists compared 1-, 2-, 3- and 7-year post-harvest data with pre-harvest information. Findings indicate that the understory vegetation is very resilient, often approaching pre-harvest condition within a few years. Scientists also found that expansion of invasive plant species appears to be restricted to a few heavily disturbed sites. Although much of the post-harvest focus is usually on trees, the understory vegetation is largely responsible for providing ecosystems services such as cycling nutrients and maintaining biological diversity.