The researchers studied how different factors like altitude and wetness affect the number of plant species in a specific area in Eastern China. They looked at the relationship between these factors and plant diversity by analyzing data from Kaihua County. The results showed that altitude and wetness have a significant impact on the number of plant species present. Plant diversity increases with altitude up to a certain point, and wetter areas tend to have more plant species. However, factors like slope and aspect did not show a clear relationship with plant diversity. The researchers used different models to predict plant diversity, with the Generalized Additive Model showing a strong correlation with the actual number of plant species observed. This study helps us understand how topography influences plant diversity in the middle sub-tropical region of Eastern China.