Niche and Interspecific Associations of Understory Vegetation Communities in Remnant Urban Mountain Vegetation

(1) the herbaceous layer exhibited the greatest sensitivity to urbanisation, with a marked decline in species diversity (Shannon-Wiener Diversity Index, Margalef Index) in highly urbanised regions, accompanied by a significant increase in ecological niche differentiation; (2) conversely, the shrub layer demonstrated enhanced ecological niche stability and favorable interspecific relationships, with species such as Zanthoxylum planispinum experiencing substantial niche expansion, particularly in urbanised areas. Other species exhibited considerable ecological niche expansion. (3) Soil variables, such as organic carbon, pH, and total phosphorus, significantly influenced community diversity, with varying driving mechanisms along the urbanisation gradient. In conclusion, by changing soil conditions and interspecific competition patterns, the urbanisation gradient impacts the richness and organisation of understory plant communities. This discovery advances our knowledge of the "urban ecosystem filter" notion and offers a solid scientific foundation for managing urban green spaces and preserving biodiversity.