Diversity patterns of medicinal plants along elevational gradients across forest layers in Meihua Mountains, Fujian

Introduction Elucidating the diversity patterns and elevational distribution of medicinal plants is essential for biodiversity conservation and sustainable utilization in montane ecosystems. However, the variation in diversity across forest vertical layers and its responses to environmental gradients in mid-subtropical regions remain poorly understood. Methods We surveyed medicinal plants in 93 plots across five elevational gradients (450–1800 m) in Meihua Mountain National Nature Reserve, China. Species composition and community structure in the tree, shrub, and herb layers were analyzed using importance values, α -diversity indices, and β-diversity metrics. Principal coordinate analysis (PCoA) and correlation analysis were performed to examine diversity patterns and identify their environmental drivers, respectively. Results A total of 503 medicinal plant species (267 genera, 98 families) were recorded. Species richness followed the order shrub herb tree layer. Community composition showed clear elevational replacement. α -diversity declined overall with elevation, with significant unimodal patterns in shrub and herb layers but no clear trend in the tree layer. Species turnover was highest in the shrub layer and lowest in the tree layer, peaking at low to mid elevations. Elevation exerted stronger effects on β -diversity in shrub and herb layers than in the tree layer. Canopy closure was negatively correlated with shrub-layer α -diversity, whereas longitude and slope were positively associated with tree- and herb-layer diversity, respectively. Discussion This study demonstrate that medicinal plant diversity in mid-subtropical mountains is jointly shaped by vertical stratification and environmental filtering. The higher sensitivity of shrub and herb layers highlights their key role in maintaining biodiversity, whereas tree-layer stability reflects greater resistance to environmental variation. Canopy structure regulates understory diversity, with additional layer-specific effects from topographic and spatial factors. These results provide new insights into diversity maintenance mechanisms and offer guidance for conservation and forest management of medicinal plant resources.