Objectives This study aims to investigate the seed plant resources in the Liulianling Provincial Nature Reserve of Hainan Province and conduct a biogeographical analysis. The goal is to understand the distribution patterns of seed plants within the reserve, thereby providing a scientific basis for biodiversity conservation, resource utilization, and ecological construction.

Methods A combination of field surveys using line transects and sample plots, supplemented by a literature review, was employed. We established 15 transects and 15 plots to collect data. The species composition, the areal-types of families and genera, and the species diversity characteristics of the seed plant flora were analyzed.

Results The results indicated that: (1) A total of 512 seed plant species belonging to 324 genera and 104 families were recorded in the reserve. Among them, gymnosperms accounted for 3 species, 3 genera, and 3 families; dicotyledons accounted for 440 species, 265 genera, and 86 families, and monocotyledons accounted for 69 species, 56 genera, and 15 families. (2) Small families and monotypic families accounted for 46.15% and 39.42% respectively of all the families; monotypic genera accounted for 73.46% of the total genera. (3) The geographical elements of both families and genera in the reserve were distinctly tropical in nature. The families can be classified into 10 areal-types and 9 subtypes, with pantropical distribution being dominant. The genera were categorized into 13 areal-types and 7 subtypes, among which pantropical distribution and tropical Asia distribution account for 24.07% and 22.84% of the non-cosmopolitan genera, respectively. (4) The species diversity index was highest in the shrub layer, followed by the tree layer, and lowest in the herb layer. The Shannon-Wiener index, Simpson dominance index and Pilou evenness index all exhibited consistent trends across these vertical layers.

Conclusions The seed plant diversity in the reserve was rich, and its floristic composition was complex. Therefore, future conservation and management efforts should prioritize the scientific preservation of transitional flora and the maintenance of diverse vegetation structural layers.