Abstract: [Objective] The study was intended to understand the characteristics of community structure of the mixed forest of subtropical evergreen and deciduous broad-leaved trees in Mulinzi National Nature Reserve, Hubei Province.[Method] A 15 hm² large plot was established following the field protocol of the CTFS in 2014 in Mulinzi National Nature Reserve, Hubei Province. All freestanding trees with diameter at breast height (DBH) ≥1 cm were mapped and identified to species.[Result] In the studied community, species richness and abundance increased with the decrease of tree heights in vertical layers, and decreased with the increase of DBH,, and the DBH classes showed an inverse J-shape. Ten species types were classified according to the diameter classes, most species were mainly distributed in the smaller diameters. Some dominant populations were clustered in one special class or evenly distributed in each class, this situation indicated that dominant species would have a concentrated or successive regeneration. Eurya alata was the dominant species of DBH<10 cm, and Fagaceae species were the dominant species in other DBH classes. Over 60% individuals of most populations were mainly distributed at the lowest tree layers, and the DBH of over 85% individuals was less than 10 cm, which suggested that these species have good regeneration, and the populations were in progressive succession. Based on the characteristics of height and DBH classes, the 25 dominant species were divided into 4 types. 16 species such as Quercus engleriana, Padus avium, and Cyclobalanopsis multinervis showed expanding populations; 3 species such as Betula luminifera, Populus adenopoda and Populus lasiocarpa were stabilizing recently but would become recession in future; 2 species including Fagus lucida and Castanea henryi displayed declining population; and 4 species (Quercus fabri, Cyclobalanopsis phanera, Tilia chinensis and Fagus engleriana population) showed alternative increasing and declining and fluctuation of the number of individuals.[Conclusion] It is concluded that the freestanding trees were small in the mixed forest of subtropical evergreen and deciduous broad-leaved trees in Mulinzi National Nature Reserve, trees of large DBH and height classes were few. Most dominant populations and even the communities were at the stage of progressive succession with good natural regeneration.

Key words: forest dynamic plot, evergreen and deciduous broad-leaved mixed forest, vertical structure, diameter class, Mulinzi Nature Reserve