[Decade dynamics of species composition and diversity of mountaintop mossy dwarf forest on the Yangming Mountains, Hunan Province, China.]

Three monitoring plots were established in the Yangming Mountains mossy dwarf forest concentration zone in the Yangmingshan National Nature Reserve in Hunan Province in 2005. The changes of species composition and diversity during 2005-2016 were analyzed from species numerical characteristics, species importance value, diameter class structure, height structure, and species diversity. The results showed that from 2005 to 2016, the individual number for ≥1.0 cm diameter at ground height (DGH) in tree layer decreased by 30.9%. Viburnum dilatatum decreased greatest with 98.6%, and Rhododendron fortunei decreased least with 1.8%. Species richness was increased, and evenness was decreased. Except for R. fortunei, the importance values of all the species decreased significantly after ten years, indicating that R. fortunei was the dominant species in the dwarf forest. The diameter-class distribution of species in the dwarf forest was arranged at 1 cm level. The density of small-diameter (1 cm≤DGH＜6 cm) species was higher, but that of medium-diameter (6 cm≤DGH＜15 cm) and large-diameter (15 cm≤DGH) was lower. The diameter-class distribution of R. fortunei exhibited a reversed 'J' shape, and the height of community increased from 2005 to 2016, indicating the population had a stable and well-developing trend. The other species were poorly renewed and their diameter-class structure was irregular. Generally, the Patrick and Menhinick richness indices and the Simpson index were increased, and the Shannon and Pielou indices were decreased during the ten years.