ABSTRACT This study analyzed the understory plant diversity and influencing environmental factors in the Ghimbo Bonca Lida Customary Forest, Kampar, Riau. Data were collected in April–May 2025 using systematic sampling on 13 plot lines (2x2m subplots). Identified results showed 41 understory species from 25 families. The Shannon-Wiener Diversity Index (H') was high for herbs (H' = 3.27) …