As one of the most extensive terrestrial ecosystems, forests support diverse ecological functions but are increasingly threatened by disturbance and degradation. Landslides have become one of major causes of forest disturbance due to the increased frequency of their occurrence in recent decades. Landslides, along with subsequent soil erosion, create new biotic and abiotic environmental conditions. , These newly created conditions could govern post-landslide succession and colonization success of seedlings. However, this process remains poorly understood. At a fine scale, interactions among seedlings with different identities (e.g., species and genotype) are expected to shape colonization through affecting seedling performance. Plant interactions, particularly facilitation, may play a crucial role in post-landslide succession but have not received sufficient attention. Meanwhile, rill erosion, which is a fine-scale soil erosion driven by water flow and soil movement following a landslide, has yet to be explored in terms of its impact on newly colonized seedlings. This study examines how these new biotic and abiotic conditions interact to shape seedling performance, aiming to provide insights for forest restoration in landslide-affected areas.

This study was conducted in an artificial landslide experiment with three replicates, which featured an approximately homogeneous initial environment. During the first growing season, we continuously monitored the performance of newly colonized seedlings of Abies sachalinensis (hereafter, Abies) in these post-landslide areas. The spatial distance between Abies seedlings and conspecific/heterospecific neighbors, the genetic distance between focal seedlings and conspecific neighbors based on SNPs obtained by MIG-seq, and the spatial distance from the seedlings to the rill edge were used as measurements of biotic and abiotic influences.

In the post-landslide area, newly recruited Abies seedlings primarily exhibited spatial clustering with conspecific neighbors. Neighbor identity and rill erosion interacted to influence the survival of focal Abies seedlings. Proximity to heterospecific neighbors significantly improved seedling survival, whereas survival decreased near rills. On the other hand, the three adjacent populations estimated were generally genetically clustered according to sites, and there was significant genetic differentiation among them. The influence of the genetic distance between focal seedlings and their nearest neighbors on the growth of the focal seedlings significantly depends on their spatial distance. The higher genetic relatedness promoted the growth of focal seedlings within close spatial distance, while this relationship reversed when the spatial distance increased.

Our study indicates that fine-scale biotic and abiotic conditions play a role in interactively shaping seedling performance.