A large-scale field experiment of artificially caused landslides with replications revealed the response of the ground-dwelling beetle community to landslides

Precipitation-induced landslides, which are predicted to increase under the changing climate, may have large impacts on insect community properties. However, understanding of how insect community properties shift following landslides remains limited because replicated research involving landslides, which are large-scale disturbances with stochastic natural causes, is difficult. To tackle this issue, we conducted a large-scale field experiment by artificially causing landslides at multiple sites. We established 12 landslide sites, each 35 m x 35 m, and 6 undisturbed sites in both planted and natural forests and collected ground-dwelling beetles 1 year later. We found that forest type (i.e., pre-disturbance vegetation) did not affect the structure of a ground-dwelling beetle community disturbed by a landslide (landslide community), but the structure of an undisturbed community was affected by forest type. Moreover, the structures of landslide and undisturbed communities were completely different, possibly because landslides create harsh environments that act as an ecological filter. Thus, a niche-selection process may have a critical role in community assembly at landslide sites. There were no significant differences in species diversity between undisturbed and landslide communities, suggesting that landslides to not reduce species richness overall. However, among-site variability in species composition was much greater at landslide sites than at undisturbed sites. This result suggests that stochastic colonization predominated at the landslide sites more than undisturbed sites. Synthesis and applications. Overall, our results suggest that both deterministic and stochastic processes are critical in community assembly, at least in the early post-landslide stage. Our large-scale manipulative field experiment with replications has thus resulted in new insights into biological community properties after a landslide.