Reduced rodent-mediated seed dispersal at forest edge hinders regeneration

Nearly 20 % of the world's remaining forests are within 100 m of an edge, and over 70 % of the world's forests are within 1 km of a forest edge, highlighting widespread forest fragmentation in global tree cover. While forest edges, particularly those resulting from anthropogenic activities such as timber harvesting and deforestation, have been extensively studied for their ecological significance and high biodiversity, the impacts of plant-animal interactions on forest regeneration across edge-to-interior gradients remain poorly understood. We hypothesized that edge effects impede forest regeneration by disrupting rodent-mediated seed dispersal, potentially exacerbating edge influence. To test this, we examined the seed dispersal patterns of Quercus wutaishanica mediated by rodents across four forest edge-to-interior distance gradients (0, 20, 40, and 60 m) in Dongling Mountain, located in the Taihang Mountains of China, using a plastic-tagged seed tracking method to monitor the dispersal dynamics. The results demonstrated that distance from the forest edge significantly influenced seed dispersal and predation by rodents, with seed removal rates increasing significantly as distance from the forest edge increased. Notably, a higher proportion of seeds were intact in situ at the forest edge, while the proportion of scatterhoarding activity was predominantly observed in the forest interior. Although seed dispersal distance exhibited a gradual increase with greater distance from the forest edge, this trend was not statistically significant. Furthermore, only one seedling survived during the following spring, located 40 m from the forest edge. These findings indicate that reduced rodent-mediated dispersal efficiency near edges creates a spatial bottleneck for regeneration, potentially exacerbating edge degradation through delayed recruitment.