Abstract:

Aims Understanding the spatial patterns and maintenance mechanisms of biodiversity is one of the central issues in ecology and biogeography. Specifically, altitudinal patterns of biodiversity have been widely explored to represent to mimic the latitudinal patterns. However, previous studies on altitudinal patterns of plant diversity have focused mainly on the taxonomic diversity, with less attention paid to the comprehensive information of taxonomic, phylogenetic evolution and functional traits. In this study, we explored maintenance mechanisms of diversity of forest communities in Mount Guandi, by comparing the altitudinal patterns of taxonomic, phylogenetic and functional diversity, based on the systematic investigation of forest communities.
Methods 52 forest plots, each with an area of 30 m × 20 m and divided into six subplots (10 m × 10 m), were investigated along the altitudinal gradient (1 409-2 150 m) in Mount Guandi, Shanxi. Name, diameter at breast height (DBH) and height were identified and measured for each tree stem with DBH ≥3 cm at each plot; name, average height, coverage and basal diameter for each shrub species were identified and measured in two of the six subplots; name, abundance, coverage and average height for each herbaceous species were identified and measured for one quadrat of 1 m × 1 m in each subplot. The indices of taxonomic, phylogenetic and functional α and β diversity were then calculated.
Important findings Species richness (S), phylogenetic diversity (PD) and functional richness (FRic) increased along the altitudinal gradient, especially in altitudes above 1 800 m. Total β diversity (β_total) and replacement β diversity (β_repl) increased, while the richness difference (β_rich) decreased, along the altitudinal gradient. The patterns of taxonomic, phylogenetic and functional diversity were significantly different between woody and herbaceous plants. S and Shannon-Wiener diversity (H′) of herbaceous plants increased more obvious along the altitude than those of woody plants. Topographic factors regulated the pattern of the herbaceous plant richness, while historical process regulated the woody plant richness. Along the altitude, β_total increased more obvious for the woody plants than for the herbaceous plants. β_repl and β_rich of woody plant showed a unimodal pattern and U-shaped pattern, while those of herbaceous plants increased or decreased, respectively. Taxonomic, phylogenetic and functional β diversity of both woody and herbaceous plants among communities increased with the environmental and geographical distances. Environmental distance had a relatively stronger effects than geographical distance on β diversity of woody plants, while environmental distance and geographical distance jointly influenced β diversity of the herbaceous plants.

Key words: taxonomic diversity, phylogenetic diversity, functional diversity, altitudinal pattern, forest community, Mount Guandi