Background Seed production and seed morphological traits are two important biological indicators of plant fruiting, reflecting the reproductive potential and adaptability of plants to the environment. The variation of seed production and morphological traits is common in woody plants and affects population dynamics, community species composition, and the maintenance of biodiversity. Thus, the interannual variation of seed production and seed morphological traits of Castanopsis fargesii were analyzed at population and individual levels. On this basis, the reproductive strategy of C. fargesii was discussed, so as to provide a data support for large-scale research on the dynamics of plant fruiting.

Methods Taking the 23 individuals in 0.50 hm² permanent monitoring plot of evergreen broad-leaved forest in Jinyun Mountain as the research object, we collected the seeds from 2013—2021. First the number of seeds were counted, then seed mass was weighted, seed height and width were measured after being air-dried. Seed production was defined as seed density, then the interannual coefficients of variation of seed production and morphological traits at population-level and individual-level were calculated, respectively. We used generalized linear mixed models to analyze the relationship between seed production and seed morphological traits.

Results 1) Totally 36 572 mature seeds of C. fargesii were collected during 9 years, and the seed production was 98.30 seeds/(m²·a); The interannual variation of seed production was significant both at population-level and individual-level (P < 0.05), among which the production in 2014, 2018 and 2021 were significantly higher than those in other years. 2) The average seed mass was (0.50±0.19) g, and the average coefficient of variation was 0.39. The ratio of height to width was relatively stable between years, the average coefficient of variation was 0.04. The variation of seed mass and H/W ratio of C. fargesii mainly came from inter-individuals, with the average Gini coefficients were 59.16% and 69.77%, respectively.

Conclusions 1) The seed production of C. fargesii showed clear masting signs, and the interval was about 3-4 years. The reproductive ability of different individuals in the population was quite different. 2) The intraspecific variation of seed mass and H/W ratio of C. fargesii was at a high level, which mainly from the inter-individuals. In addition, the seed mass also differed interannually, and it decreased with the increase of seed production, which suggested that mast-seeding may led to the reduction of seed mass. In contrast, the H/W ratio of seed was relatively stable between years, and had no significant correlation with seed production.