Cong Zhou, Akihiro Nakamura, Xiaoyang Song, Masatoshi Katabuchi

Artificial light at night (ALAN) demonstrated a new ecological factor that influences organisms through multi-approach. Yet, the impacts of ALAN on understory plants remain largely unknown. We evaluated whether ALAN would affect leaf mass per area (LMA) of understory plants through a two-year field light experiment in a tropical rubber plantation in south China. We hypothesized that ALAN could impact the understory in two ways: by directly supplementing light to aboveground plant parts (which increases LMA) and indirectly affecting soil nutrient composition by attracting insects (which decreases LMA). We selected two species: Colocasia gigantea, representing shade-torelant species, and Melastoma candidum, representing light-demanding species. We measured canopy openness, LMA, soil nutrients, and individual distance away from light resources. We found a negative relationship between LMA and the strength of ALAN, indicating that ALAN may influence LMA more indirectly by enhancing soil nutrient availability rather than directly acting as a light resource. This relationship was significant for Colocasia gigantea but not for Melastoma candidum. These results suggest that ALAN might have complex and species-specific impacts on the understory ecosystem.