The researchers studied the diversity of plant species in European forests. They counted the number of different plant species in over 73,000 forest plots and used computer models to understand why some areas have more plant species than others. They found that areas with more diverse plant species tend to be in the southeastern part of Europe. Factors like temperature, type of rock, and terrain shape play a big role in determining plant diversity. This information helps us better understand the variety of plants in European forests and how different factors affect their growth.