The relative importance of drought stress and neighbor richness on plant- plant interactions shifts over a short time

Exploring how plant-plant interactions between species and their neighbors vary with biotic and abiotic factors is vital to understanding community assembly mechanisms in the context of global changes. In this study, using a dominant species (Leymus chinensis (Trin.) Tzvel.) in the semiarid Inner Mongolia steppe as the target species and ten other species as neigh-bors, we carried out a microcosm experiment to evaluate how drought stress, neighbor richness and season affected the relative neighbor effect (Cint) (the ability to reduce growth of target species). The factor of season interactively affected the effect of drought stress or neighbor richness on Cint. In the summer, drought stress decreased Cint directly and indirectly by decreasing SLA hierarchical distance and neighbor biomass. In the subsequent spring, drought stress increased Cint, and neighbor richness increased Cint directly and indirectly by increasing neighbor community functional dispersion (FDis) and neighbor biomass. Specifically, SLA hierarchical distance was positively associated with neighbor biomass, while height hierarchical distance was negatively associated with neighbor biomass in both seasons, which increased Cint. These findings show that the relative importance of drought stress and neighbor richness on Cint shifted over seasons, which provides strong empirical evidence of how plant-plant interactions respond to changes in biotic and abiotic factors in the semiarid Inner Mongolia steppe over a short-term time. Furthermore, this study provides novel insight into commu-nity assembly mechanisms in the context of climatic aridity and biodiversity loss in semiarid regions.

Automated summary

This study investigated how drought stress, neighbor richness, and season affected the relative neighbor effect in the semiarid Inner Mongolia steppe. The results showed that the effects of drought stress and neighbor richness on the neighbor effect depended on the season. These findings provide empirical evidence of the dynamic nature of plant-plant interactions in response to biotic and abiotic factors.