Long-term ecological change is often hard to document without reliable baseline data. We obtained baseline data for and resurveyed 80 forest understory communities in Wisconsin first surveyed 50 yr ago. Sixty-two sites were in the forested region of northern Wisconsin, and 18 were in the agricultural region of southern Wisconsin. For 50 yr, the number of sites with nonnative plants increased from 4 to 62. Species richness in 1950 had little influence on nonnative species establishment by 2002, and nonnative species did not seem to influence rates of native species loss over time.

Additional index words: Ecologically invasive, forest, monitoring, plant, species loss, Wisconsin.