The researchers studied how plant communities change on Mt. Mao'er in China as you go higher up the mountain. They looked at 16 different areas at different altitudes and found that the types of trees and plants varied a lot. Trees were tallest in the middle of the mountain, but there were more different types of trees at lower altitudes. The number of tree species decreased as you went higher up. The diversity of plants was lower at higher altitudes. The areas closer together had more similar plants than areas further apart. The main factor affecting the plants was how high up they were on the mountain, not the slope or direction they faced.