Ecological niches and interspecific associations of dominant species in herbaceous communities at karst valley waterfall sources in Hunan Dehang Geopark

This study explored the niche characteristics, interspecific relationships, and stability of dominant species within the herbaceous communities located at the sources of three waterfalls in Dehang Geopark. A comprehensive analytical framework integrating niche width estimation, variance ratio (R_V), χ² testing, Spearman rank correlation, association coefficient (AC), and M. Gordon stability assessment was applied. Results indicated that: (1) Artemisia indica Willd. at Dalongdong Waterfall, Oenanthe javanica (Blume) DC. and Pilea notata C. H. Wright at Liusha Waterfall, and Gynostemma pentagynum Z. P. Wang at Xiannv Waterfall exhibited the broadest niche widths. Overall niche overlap values were low, with many species pairs showing zero overlap, reflecting weak interspecific competition and limited similarity in resource utilization among dominant taxa. (2) Interspecific associations were not significantly negative, and the χ² test, Spearman correlation, and C_A values collectively revealed that dominant species were largely distributed independently, characterized by low degrees of association. (3) M. Gordon stability analysis demonstrated that herbaceous communities across the three waterfall regions maintained relatively high stability, with the Xiannv Waterfall community exhibiting the greatest resilience, followed by Dalongdong Waterfall, and Liusha Waterfall showing comparatively lower stability. Notably, community stability did not exhibit a positive correlation with the strength of interspecific associations.