Abstract: Wuyi Mountain is the key region of highest biodiversity in southeast China, and its peak Huanggang Mountain has a typical altitudinal belt of subtropical vegetation on the northwestern slope. In order to better understand the variations in plant species diversity along the altitudinal gradient, five altitudinal ranges with distinct vegetation types were selected on the northwest slope of Huanggang Mountain (900-2000 m, and denoted by gradients 1, 2, 3, 4 and 5 from low to high altitudes), and α and β diversity indices were used to quantify plant species diversity. The results showed that the mean richness of families, genera, and species in communities as well as the mean individuals and species of trees followed a decreasing trend with the increase of  the elevation, and gradient 1 showed significant differences with gradients 3, 4 and 5 (P<0.05). α diversity index also showed a decreasing trend with the increase of altitude. Gleason richness index of gradient 1 showed significant differences with gradients 3, 4 and 5 (P<0.05), but Shannon diversity index of gradient 1 only showed a significant difference with that of the gradient 5 (P<0.05), while Pielou evenness index did not show significant difference (P>0.05). However, β diversity index and mean species density followed a V-typed trend (firstly decrease, and then increase) in the different gradients. Diversity indices of trees didn’t show the same trend as the communities, but the difference of Pielou index showed the same results in the different gradients. Taken together, the results indicated that the communities in low altitudinal gradient were characterized by high plant diversity, while that in middle altitudinal gradient showed lowest density.

Key words: Pinus elliottii, red soil, nitrogen addition, hydrolase activity, oxidase activity