Landform and lithospheric development contribute to the assembly of mountain floras in China.

Although it is well documented that mountains tend to exhibit high biodiversity, how geological processes affect the assemblage of montane floras is a matter of ongoing research. Here, we explore landform-specific differences among montane floras based on a dataset comprising 17,576 angiosperm species representing 140 Chinese mountain floras, which we define as the collection of all angiosperm species growing on a specific mountain. Our results show that igneous bedrock (granitic and karst-granitic landforms) is correlated with higher species richness and phylogenetic overdispersion, while the opposite is true for sedimentary bedrock (karst, Danxia, and desert landforms), which is correlated with phylogenetic clustering. Furthermore, we show that landform type was the primary determinant of the assembly of evolutionarily older species within floras, while climate was a greater determinant for younger species. Our study indicates that landform type not only affects montane species richness, but also contributes to the composition of montane floras. To explain the assembly and differentiation of mountain floras, we propose the 'floristic geo-lithology hypothesis', which highlights the role of bedrock and landform processes in montane floristic assembly and provides insights for future research on speciation, migration, and biodiversity in montane regions.

[Natural regeneration of young Excentrodendron hsienmu in karst mountainous region in Southwest Guangxi, China].

A field survey was conducted in the karst mountainous region in Pingguo County of Southwest Guangxi, China to explore the structural characteristics, spatial distribution pattern, and growth dynamics of young Excentrodendron hsienmu as well as the main environmental factors affecting the natural regeneration of the E. hsienmu population. In the study area, the population structure of the young E. hsienmu was stable, and exhibited a clumped spatial pattern for the seedlings and seedling sprouts. The ground diameter growth and height growth of the young E. hsienmu presented the same variation trend, i. e., the ground diameter increased with increasing height. The ground diameter growth and height growth of the E. hsienmu seedlings were limited by population density, i. e., decreased with increasing population density. The correlation analysis showed that the trees more than 2.5 m in height and the shrubs were the major stand factors affecting the natural regeneration of young E. hsienmu, while the herbs had no significant correlation with the regeneration. The percentage of covered rock also had no significant effects on the regeneration. Kruskal-Wallis ANOVA showed that there existed significant differences in the height and ground diameter of young E. hsienmu at different slope degrees and slope positions. The population density, height, and ground diameter had significant differences across slope aspects. The natural regeneration of young E. hsienmu was comprehensively affected by the species biological characteristics, intraspecific competition, interspecific competition, heterogeneous habitat, and anthropogenic disturbances.

[Effects of topographic factors on the distribution patterns of ground plants with different growth forms in montane forests in North Guangdong, China].

By using canonical correspondence analysis (CCA), this paper studied the effects of small-scale topographic changes on the distribution patterns of ground plants with different growth forms in the montane evergreen broad-leaved forest in Chebaling National Nature Reserve of North Guangdong, China. It was observed that slope aspect, slope grade, and slope position had significantly integrative effects on the distribution patterns of four growth form ground plants (fern, liana, herb, and shrub). Slope aspect had significant effects on the distribution patterns of all four ground plants but slope position didn't have, whereas slope grade only affected the distribution pattern of shrub significantly. From shady slope to semi-shady slope, and to semi-sunny slope, the abundance of the four growth form ground plants decreased gradually, indicating that shade plants were dominant in the ground vegetation of subtropical montane evergreen broad-leaved forest. Most shrubs were shade-tolerant species, and their change patterns of richness and diversity with slope aspect were the same as the change pattern of abundance. Shrubs were sensitive to the change of slope grade, and richer on gentle slopes. In hilly and low mountains, slope position changed little, and had less effects on the distribution patterns of ground plants. At stand-level, horizontal topographic factor (slope grade aspect) had much greater effects on the distribution patterns of ground plants, as compared with vertical topographic factors (slope grade and slope position), which suggested that slope aspect was the major factor affecting the water and heat conditions in subtropical montane forest.