Species composition and community structure of a 20 hm2 plot of mid-mountain moist evergreen broad-leaved forest on the Mts. Ailaoshan, Yunnan Province, China

Abstract

Aims: The mid-mountain moist evergreen broad-leaved forest is a montane forest vegetation type developed in the subtropical climate zones of China. However, the community structure of the forest has never been reported based on large sized plots. The present study investigated the tree species composition and community structure within a 20 hm2 plot, serving as the fundamentals for analyzing the relationships between environmental factors and spatial distribution of tree species, and a basic platform for monitoring long-term forest dynamics in the future. Methods: We established a 20 hm2 plot in a forest at Xujiaba on Mts. Ailaoshan, Jingdong County, Yunnan Province in 2014. The plot was set up in accordance to the protocols of the Center for Tropical Forest Science (CTFS). All free-standing woody plants with a diameter at breast height (DBH) 1 cm were positioned, mapped, tagged, measured and identified to species in the plot. Important findings :A total of 44 168 free-standing individuals with DBH 1 cm were recorded, belonging to 104 species, 63 genera and 36 families. Trees of Fagaceae, Theaceae and Lauraceae are dominant species. At the level of genus, the floristic composition was primarily represented by both tropical (46.0%) and temperate (38.1%) elements. The 22 individual species with importance value d 1 contributed 84.6% to the total abundance. The three most abundant species were Camellia forrestii, Vaccinium duclouxii and Symplocos ramosissima. Four tree species (Lithocarpus hancei, L. xylocarpus, Castanopsis wattii and Schima noronhae) had the largest basal areas, and they were also the dominant canopy tree species in the plot. The DBH distribution of all individuals in the plot showed a reversed J pattern, indicating numerous recruiting populations. Such a pattern was applicable to C. forrestii and S. ramosissima as well. Forty-nine rare species (those with individual number fewer than 20 in the plot) accounted for 47.1% of the species total. Evergreen species dominated the life form spectrum of the plot, making up for 94.7%, 96.2% and 94.0% in terms of importance value, total abundance and total basal area, respectively.