Abstract:

Aims: The Nanling mountains serve as a key ecological corridor and transition zone between the mid- and south-subtropical regions of China. Both the tropical and temperate floras converge in this region, and therefore it is the northern or southern distributional boundaries of many plant species. 

Methods: Based on 16 1-ha forest dynamic monitoring plots established across the Guangdong Nanling National Nature Reserve, covering all main vegetation types spanning the whole region, we analyzed the species composition, floristic characteristics, size distribution, and spatial distributions of woody plants with ≥ 1 cm DBH (diameter at breast height). 

Results: There were 75,141 individual trees and shrubs (100,923 stems including branches) in these 16 plots, belonging to 582 species, 220 genera, and 78 families. Among them, we identified 137 tropical genera (398 species; 62% of total genera, 68% of total species) and 80 temperate genera (174 species; 36% of total genera, 30% of total species), and 3 cosmopolitan genera (10 species). The plot with the highest richness had 229 species, while the plot with the lowest had only 87 species. The dominant species in the tree layer varied across plots, effectively representing the main forest types in the Nanling Mountains. Overall, all the plots exhibited stable inverse J-shaped size distributions for all the individuals together, but dominant species in each plot and the same species among the plots varied considerably in size distribution. The results of species-area curves suggested dramatic differences in the species accumulation rates and saturation thresholds among the 16 plots. On average, when a 400 m² plot is sampled, only 30% of total plant richness is covered, while 90% species coverage is achieved when the plot size of 6,600 m².is surveyed. Spatial distribution patterns varied significantly across different vegetation types and diameter classes. Dominant species showed distinct habitat preferences, and the same species (e.g., Schima superba and Pinus massoniana) displayed divergent spatial patterns across plots. 

Conclusion: This study demonstrates large variations in plant species composition, community structure, and species’ spatial distributions among distinct vegetation types of the Nanling Mountains. These results provide the basis for long-term biodiversity monitoring in subtropical montane forests and the development of the national park network.

Key words: Nanling Mountains, subtropical forest, evergreen broad-leaved forest, community structure, species diversity