Objective This paper investigates the composition and structural characteristics of woody plants in the permanent monitoring sample plots of Niumulin Nature Reserve, Fujian Province of eastern China, aiming to provide an important reference for deeper understanding of vegetation diversity.

Method Taking the Niumulin Nature Reserve in Fujian Province as research subject, a 3.04 ha permanent monitoring sample plot was established within the reserve. Woody plants with DBH≥ 1 cm within the sample plot were surveyed and identified. The species composition, diameter and height class structure, species and abundance accumulation curve, and stand structure characteristics of the sample plots were analyzed.

Result (1) A total of 121 woody plant species with DBH ≥ 1 cm were identified in Niumulin, belonging to 36 families and 64 genera. The top three species by importance value were Castanopsis carlesii, Pinus massoniana, and Eurya loquaiana, all with importance values less than 0.1, the dominance of these species was not significant. Common, occasional, and rare species accounted for 50.41%, 23.97%, and 25.62% of the total species, respectively. (2) The relationship between number of sample plots and species richness showed a sharp increase in species with less than 13 sample plots, followed by a decrease in the rate of increase thereafter. (3) The structure of DBH was similar to that of height structure, both following an inverted “J”-shaped pattern. Dominant species like C. carlesii and E. loquaiana showed an increasing type in DBH class structure, while P. massoniana exhibited a declining type. (4) Except for individual density, 19 sample plots showed no significant differences in breast height per unit stand area, volume per unit stand area and biomass per unit stand area. The mean biomass per unit stand area of the Niumulin sample plot was 270.84 t/ha.

Conclusion These results indicate that the Niumulin forest is rich in species, but the dominant species are not prominent and belong to the growth type. The stand productivity is slightly lower than that of the average in Fujian Province. However, with forest succession and development, the stand productivity of this forest will have great growth potential in the future.