The researchers studied tree and shrub diversity in oak forests in Ilam province. They looked at how factors like elevation, slope, and aspect, as well as stand characteristics like canopy density and number of trees, affected the variety of species. They found that the middle elevation areas had the most species, while south-facing slopes had the most diversity. As slopes increased, diversity generally increased but then decreased after 60%. Canopy density and number of trees had a positive relationship with species richness but a negative relationship with diversity and evenness.